[uml-devel] [PATCH] um: Switch clocksource to hrtimers

[uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Thomas Meyer]

Switch the UML clocksource from interval timers to posix interval timers
and move to a monotonic timer.

This fixes suspend&resume related timer issues and improves network
performance as TCP state machines are now fed with the correct time;
also correct QoS and traffic shaping.

Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
---

diff --git a/arch/um/Makefile b/arch/um/Makefile
index e4b1a96..43ef190 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -130,7 +130,7 @@ export LDS_ELF_FORMAT := $(ELF_FORMAT)
 # The wrappers will select whether using "malloc" or the kernel allocator.
 LINK_WRAPS = -Wl,--wrap,malloc -Wl,--wrap,free -Wl,--wrap,calloc
 
-LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt))
+LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt)) -lrt
 
 # Used by link-vmlinux.sh which has special support for um link
 export CFLAGS_vmlinux := $(LINK-y) $(LINK_WRAPS) $(LD_FLAGS_CMDLINE)
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 08eec0b..5949cae 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -219,7 +219,7 @@ extern int set_umid(char *name);
 extern char *get_umid(void);
 
 /* signal.c */
-extern void timer_init(void);
+extern void timer_set_signal_handler(void);
 extern void set_sigstack(void *sig_stack, int size);
 extern void remove_sigstack(void);
 extern void set_handler(int sig);
@@ -240,12 +240,16 @@ extern void um_early_printk(const char *s, unsigned int n);
 extern void os_fix_helper_signals(void);
 
 /* time.c */
-extern void idle_sleep(unsigned long long nsecs);
-extern int set_interval(void);
-extern int timer_one_shot(int ticks);
-extern long long disable_timer(void);
+extern void os_idle_sleep(unsigned long long nsecs);
+extern int os_timer_create(void* timer);
+extern int os_timer_set_interval(void* timer, void* its);
+extern int os_timer_one_shot(int ticks);
+extern long long os_timer_disable(void);
+extern long os_timer_remain(void* timer);
 extern void uml_idle_timer(void);
+extern long long os_persistent_clock_emulation(void);
 extern long long os_nsecs(void);
+extern long long os_vnsecs(void);
 
 /* skas/mem.c */
 extern long run_syscall_stub(struct mm_id * mm_idp,
diff --git a/arch/um/include/shared/skas/stub-data.h b/arch/um/include/shared/skas/stub-data.h
index f6ed92c..f98b9e2 100644
--- a/arch/um/include/shared/skas/stub-data.h
+++ b/arch/um/include/shared/skas/stub-data.h
@@ -6,12 +6,12 @@
 #ifndef __STUB_DATA_H
 #define __STUB_DATA_H
 
-#include <sys/time.h>
+#include <time.h>
 
 struct stub_data {
-	long offset;
+	unsigned long offset;
 	int fd;
-	struct itimerval timer;
+	struct itimerspec timer;
 	long err;
 };
 
diff --git a/arch/um/include/shared/timer-internal.h b/arch/um/include/shared/timer-internal.h
new file mode 100644
index 0000000..03e6f21
--- /dev/null
+++ b/arch/um/include/shared/timer-internal.h
@@ -0,0 +1,13 @@
+/*
+ * Copyright (C) 2012 - 2014 Cisco Systems
+ * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ */
+
+#ifndef __TIMER_INTERNAL_H__
+#define __TIMER_INTERNAL_H__
+
+#define TIMER_MULTIPLIER 256
+#define TIMER_MIN_DELTA  500
+
+#endif
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index f17bca8..d0bbd01 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -27,6 +27,7 @@
 #include <kern_util.h>
 #include <os.h>
 #include <skas.h>
+#include <timer-internal.h>
 
 /*
  * This is a per-cpu array.  A processor only modifies its entry and it only
@@ -201,11 +202,8 @@ void initial_thread_cb(void (*proc)(void *), void *arg)
 
 void arch_cpu_idle(void)
 {
-	unsigned long long nsecs;
-
 	cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
-	nsecs = disable_timer();
-	idle_sleep(nsecs);
+	os_idle_sleep(UM_NSEC_PER_SEC / UM_HZ);
 	local_irq_enable();
 }
 
diff --git a/arch/um/kernel/skas/clone.c b/arch/um/kernel/skas/clone.c
index 289771d..814ec8b 100644
--- a/arch/um/kernel/skas/clone.c
+++ b/arch/um/kernel/skas/clone.c
@@ -24,6 +24,7 @@ void __attribute__ ((__section__ (".__syscall_stub")))
 stub_clone_handler(void)
 {
 	struct stub_data *data = (struct stub_data *) STUB_DATA;
+	timer_t timerid;
 	long err;
 
 	err = stub_syscall2(__NR_clone, CLONE_PARENT | CLONE_FILES | SIGCHLD,
@@ -35,8 +36,14 @@ stub_clone_handler(void)
 	if (err)
 		goto out;
 
-	err = stub_syscall3(__NR_setitimer, ITIMER_VIRTUAL,
-			    (long) &data->timer, 0);
+	/* create posix interval timer */
+	err = stub_syscall3(__NR_timer_create, CLOCK_MONOTONIC, 0l, (long) &timerid);
+	if (err)
+		goto out;
+
+	/* set interval to the given value from copy_context_skas0() */
+	err = stub_syscall4(__NR_timer_settime, (long) timerid, 0l,
+						(long) &data->timer, 0l);
 	if (err)
 		goto out;
 
diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c
index 117568d..d15966c 100644
--- a/arch/um/kernel/time.c
+++ b/arch/um/kernel/time.c
@@ -1,4 +1,5 @@
 /*
+ * Copyright (C) 2012-2014 Cisco Systems
  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  * Licensed under the GPL
  */
@@ -8,10 +9,12 @@
 #include <linux/interrupt.h>
 #include <linux/jiffies.h>
 #include <linux/threads.h>
+#include <linux/spinlock.h>
 #include <asm/irq.h>
 #include <asm/param.h>
 #include <kern_util.h>
 #include <os.h>
+#include <timer-internal.h>
 
 void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
 {
@@ -22,18 +25,20 @@ void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
 	local_irq_restore(flags);
 }
 
-static void itimer_set_mode(enum clock_event_mode mode,
+static void timer_set_mode(enum clock_event_mode mode,
 			    struct clock_event_device *evt)
 {
 	switch (mode) {
 	case CLOCK_EVT_MODE_PERIODIC:
-		set_interval();
+		os_timer_set_interval(NULL, NULL);
 		break;
 
+	case CLOCK_EVT_MODE_ONESHOT:
+		os_timer_one_shot(1);
+
 	case CLOCK_EVT_MODE_SHUTDOWN:
 	case CLOCK_EVT_MODE_UNUSED:
-	case CLOCK_EVT_MODE_ONESHOT:
-		disable_timer();
+		os_timer_disable();
 		break;
 
 	case CLOCK_EVT_MODE_RESUME:
@@ -41,68 +46,74 @@ static void itimer_set_mode(enum clock_event_mode mode,
 	}
 }
 
-static int itimer_next_event(unsigned long delta,
+static int timer_next_event(unsigned long delta,
 			     struct clock_event_device *evt)
 {
-	return timer_one_shot(delta + 1);
+	return os_timer_one_shot(delta);
 }
 
-static struct clock_event_device itimer_clockevent = {
-	.name		= "itimer",
+static struct clock_event_device timer_clockevent = {
+	.name		= "posix-timer",
 	.rating		= 250,
 	.cpumask	= cpu_all_mask,
 	.features	= CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
-	.set_mode	= itimer_set_mode,
-	.set_next_event = itimer_next_event,
-	.shift		= 32,
+	.set_mode	= timer_set_mode,
+	.set_next_event = timer_next_event,
+	.shift		= 0,
+	.max_delta_ns	= 0xffffffff,
+	.min_delta_ns	= TIMER_MIN_DELTA, //microsecond resolution should be enough for anyone, same as 640K RAM
 	.irq		= 0,
+	.mult		= 1,
 };
 
-static irqreturn_t um_timer(int irq, void *dev)
+static irqreturn_t um_timer_irq(int irq, void *dev)
 {
-	(*itimer_clockevent.event_handler)(&itimer_clockevent);
+	(*timer_clockevent.event_handler)(&timer_clockevent);
 
 	return IRQ_HANDLED;
 }
 
-static cycle_t itimer_read(struct clocksource *cs)
+static cycle_t timer_read(struct clocksource *cs)
 {
-	return os_nsecs() / 1000;
+	return os_nsecs() / TIMER_MULTIPLIER;
 }
 
-static struct clocksource itimer_clocksource = {
-	.name		= "itimer",
+static struct clocksource timer_clocksource = {
+	.name		= "timer",
 	.rating		= 300,
-	.read		= itimer_read,
+	.read		= timer_read,
 	.mask		= CLOCKSOURCE_MASK(64),
 	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
-static void __init setup_itimer(void)
+static void __init timer_setup(void)
 {
 	int err;
 
-	err = request_irq(TIMER_IRQ, um_timer, 0, "timer", NULL);
-	if (err != 0)
+	err = request_irq(TIMER_IRQ, um_timer_irq, IRQF_TIMER, "hr timer", NULL);
+	if (err != 0) {
 		printk(KERN_ERR "register_timer : request_irq failed - "
 		       "errno = %d\n", -err);
+		return;
+    }
+
+    err = os_timer_create(NULL);
+    if (err != 0) {
+        printk(KERN_ERR "creation of timer failed - errno = %d\n", -err);
+        return;
+    }
 
-	itimer_clockevent.mult = div_sc(HZ, NSEC_PER_SEC, 32);
-	itimer_clockevent.max_delta_ns =
-		clockevent_delta2ns(60 * HZ, &itimer_clockevent);
-	itimer_clockevent.min_delta_ns =
-		clockevent_delta2ns(1, &itimer_clockevent);
-	err = clocksource_register_hz(&itimer_clocksource, USEC_PER_SEC);
+	err = clocksource_register_hz(&timer_clocksource, NSEC_PER_SEC/TIMER_MULTIPLIER);
 	if (err) {
 		printk(KERN_ERR "clocksource_register_hz returned %d\n", err);
 		return;
 	}
-	clockevents_register_device(&itimer_clockevent);
+	clockevents_register_device(&timer_clockevent);
 }
 
 void read_persistent_clock(struct timespec *ts)
 {
-	long long nsecs = os_nsecs();
+	long long nsecs = os_persistent_clock_emulation();
 
 	set_normalized_timespec(ts, nsecs / NSEC_PER_SEC,
 				nsecs % NSEC_PER_SEC);
@@ -110,6 +121,6 @@ void read_persistent_clock(struct timespec *ts)
 
 void __init time_init(void)
 {
-	timer_init();
-	late_time_init = setup_itimer;
+	timer_set_signal_handler();
+	late_time_init = timer_setup;
 }
diff --git a/arch/um/os-Linux/internal.h b/arch/um/os-Linux/internal.h
deleted file mode 100644
index 0dc2c9f..0000000
--- a/arch/um/os-Linux/internal.h
+++ /dev/null
@@ -1 +0,0 @@
-void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc);
diff --git a/arch/um/os-Linux/main.c b/arch/um/os-Linux/main.c
index df9191a..6e36f0f 100644
--- a/arch/um/os-Linux/main.c
+++ b/arch/um/os-Linux/main.c
@@ -163,13 +163,13 @@ int __init main(int argc, char **argv, char **envp)
 
 	/*
 	 * This signal stuff used to be in the reboot case.  However,
-	 * sometimes a SIGVTALRM can come in when we're halting (reproducably
+	 * sometimes a timer signal can come in when we're halting (reproducably
 	 * when writing out gcov information, presumably because that takes
 	 * some time) and cause a segfault.
 	 */
 
-	/* stop timers and set SIGVTALRM to be ignored */
-	disable_timer();
+	/* stop timers and set timer signal to be ignored */
+	os_timer_disable();
 
 	/* disable SIGIO for the fds and set SIGIO to be ignored */
 	err = deactivate_all_fds();
diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
index 7b605e4..4a9be55 100644
--- a/arch/um/os-Linux/signal.c
+++ b/arch/um/os-Linux/signal.c
@@ -13,7 +13,6 @@
 #include <kern_util.h>
 #include <os.h>
 #include <sysdep/mcontext.h>
-#include "internal.h"
 
 void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
 	[SIGTRAP]	= relay_signal,
@@ -23,7 +22,8 @@ void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
 	[SIGBUS]	= bus_handler,
 	[SIGSEGV]	= segv_handler,
 	[SIGIO]		= sigio_handler,
-	[SIGVTALRM]	= timer_handler };
+	[SIGALRM]	= timer_handler
+};
 
 static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
 {
@@ -38,7 +38,7 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
 	}
 
 	/* enable signals if sig isn't IRQ signal */
-	if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGVTALRM))
+	if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGALRM))
 		unblock_signals();
 
 	(*sig_info[sig])(sig, si, &r);
@@ -55,8 +55,8 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
 #define SIGIO_BIT 0
 #define SIGIO_MASK (1 << SIGIO_BIT)
 
-#define SIGVTALRM_BIT 1
-#define SIGVTALRM_MASK (1 << SIGVTALRM_BIT)
+#define SIGALRM_BIT 1
+#define SIGALRM_MASK (1 << SIGALRM_BIT)
 
 static int signals_enabled;
 static unsigned int signals_pending;
@@ -78,46 +78,47 @@ void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
 	set_signals(enabled);
 }
 
-static void real_alarm_handler(mcontext_t *mc)
+static void timer_real_alarm_handler(mcontext_t *mc)
 {
 	struct uml_pt_regs regs;
 
 	if (mc != NULL)
 		get_regs_from_mc(&regs, mc);
 	regs.is_user = 0;
-	unblock_signals();
-	timer_handler(SIGVTALRM, NULL, &regs);
+	timer_handler(SIGALRM, NULL, &regs);
 }
 
-void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
+void timer_alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
 {
 	int enabled;
 
 	enabled = signals_enabled;
 	if (!signals_enabled) {
-		signals_pending |= SIGVTALRM_MASK;
+		signals_pending |= SIGALRM_MASK;
 		return;
 	}
 
 	block_signals();
-
-	real_alarm_handler(mc);
+	timer_real_alarm_handler(mc);
 	set_signals(enabled);
 }
 
-void timer_init(void)
+void timer_set_signal_handler(void)
 {
-	set_handler(SIGVTALRM);
+	set_handler(SIGALRM);
 }
 
 void set_sigstack(void *sig_stack, int size)
 {
-	stack_t stack = ((stack_t) { .ss_flags	= 0,
-				     .ss_sp	= (__ptr_t) sig_stack,
-				     .ss_size 	= size - sizeof(void *) });
+	stack_t stack = ((stack_t) {
+	            .ss_flags = 0,
+				.ss_sp    = (__ptr_t) sig_stack,
+				.ss_size  = size - sizeof(void *)
+	});
 
-	if (sigaltstack(&stack, NULL) != 0)
+	if (sigaltstack(&stack, NULL) != 0) {
 		panic("enabling signal stack failed, errno = %d\n", errno);
+	}
 }
 
 static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
@@ -129,10 +130,9 @@ static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
 
 	[SIGIO] = sig_handler,
 	[SIGWINCH] = sig_handler,
-	[SIGVTALRM] = alarm_handler
+	[SIGALRM] = timer_alarm_handler
 };
 
-
 static void hard_handler(int sig, siginfo_t *si, void *p)
 {
 	struct ucontext *uc = p;
@@ -186,9 +186,9 @@ void set_handler(int sig)
 
 	/* block irq ones */
 	sigemptyset(&action.sa_mask);
-	sigaddset(&action.sa_mask, SIGVTALRM);
 	sigaddset(&action.sa_mask, SIGIO);
 	sigaddset(&action.sa_mask, SIGWINCH);
+	sigaddset(&action.sa_mask, SIGALRM);
 
 	if (sig == SIGSEGV)
 		flags |= SA_NODEFER;
@@ -281,8 +281,8 @@ void unblock_signals(void)
 		if (save_pending & SIGIO_MASK)
 			sig_handler_common(SIGIO, NULL, NULL);
 
-		if (save_pending & SIGVTALRM_MASK)
-			real_alarm_handler(NULL);
+		if (save_pending & SIGALRM_MASK)
+			timer_real_alarm_handler(NULL);
 	}
 }
 
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index 908579f..f669f9d 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -47,7 +47,7 @@ static int ptrace_dump_regs(int pid)
  * Signals that are OK to receive in the stub - we'll just continue it.
  * SIGWINCH will happen when UML is inside a detached screen.
  */
-#define STUB_SIG_MASK ((1 << SIGVTALRM) | (1 << SIGWINCH))
+#define STUB_SIG_MASK ((1 << SIGALRM) | (1 << SIGWINCH))
 
 /* Signals that the stub will finish with - anything else is an error */
 #define STUB_DONE_MASK (1 << SIGTRAP)
@@ -199,12 +199,23 @@ static int userspace_tramp(void *stack)
 {
 	void *addr;
 	int err;
+	timer_t timer;
+
+	struct stub_data *data = (struct stub_data *) stack;
 
 	ptrace(PTRACE_TRACEME, 0, 0, 0);
 
 	signal(SIGTERM, SIG_DFL);
 	signal(SIGWINCH, SIG_IGN);
-	err = set_interval();
+
+	err = os_timer_create(&timer);
+	if (err) {
+		printk(UM_KERN_ERR "userspace_tramp - creation of timer failed, "
+		       "errno = %d\n", err);
+		exit(1);
+	}
+
+	err = os_timer_set_interval(&timer, &data->timer);
 	if (err) {
 		printk(UM_KERN_ERR "userspace_tramp - setting timer failed, "
 		       "errno = %d\n", err);
@@ -271,8 +282,9 @@ int userspace_pid[NR_CPUS];
 int start_userspace(unsigned long stub_stack)
 {
 	void *stack;
-	unsigned long sp;
+	unsigned long sp, remain;
 	int pid, status, n, flags, err;
+	struct stub_data *data = (struct stub_data *) stub_stack;
 
 	stack = mmap(NULL, UM_KERN_PAGE_SIZE,
 		     PROT_READ | PROT_WRITE | PROT_EXEC,
@@ -292,6 +304,18 @@ int start_userspace(unsigned long stub_stack)
 	else
 		flags |= SIGCHLD;
 
+	remain = os_timer_remain(NULL);
+	if (remain == 0)
+		remain = UM_NSEC_PER_SEC / UM_HZ;
+
+	*data = ((struct stub_data) { 
+			.timer  = ((struct itimerspec)
+				{ .it_value.tv_sec  = 0,
+				  .it_value.tv_nsec = remain,
+				  .it_interval.tv_sec  = 0,
+				  .it_interval.tv_nsec = UM_NSEC_PER_SEC / UM_HZ })
+	});
+
 	pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
 	if (pid < 0) {
 		err = -errno;
@@ -308,7 +332,7 @@ int start_userspace(unsigned long stub_stack)
 			       "errno = %d\n", errno);
 			goto out_kill;
 		}
-	} while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGVTALRM));
+	} while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGALRM));
 
 	if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
 		err = -EINVAL;
@@ -341,8 +365,6 @@ int start_userspace(unsigned long stub_stack)
 
 void userspace(struct uml_pt_regs *regs)
 {
-	struct itimerval timer;
-	unsigned long long nsecs, now;
 	int err, status, op, pid = userspace_pid[0];
 	/* To prevent races if using_sysemu changes under us.*/
 	int local_using_sysemu;
@@ -351,13 +373,8 @@ void userspace(struct uml_pt_regs *regs)
 	/* Handle any immediate reschedules or signals */
 	interrupt_end();
 
-	if (getitimer(ITIMER_VIRTUAL, &timer))
-		printk(UM_KERN_ERR "Failed to get itimer, errno = %d\n", errno);
-	nsecs = timer.it_value.tv_sec * UM_NSEC_PER_SEC +
-		timer.it_value.tv_usec * UM_NSEC_PER_USEC;
-	nsecs += os_nsecs();
-
 	while (1) {
+
 		/*
 		 * This can legitimately fail if the process loads a
 		 * bogus value into a segment register.  It will
@@ -428,19 +445,7 @@ void userspace(struct uml_pt_regs *regs)
 			case SIGTRAP:
 				relay_signal(SIGTRAP, (struct siginfo *)&si, regs);
 				break;
-			case SIGVTALRM:
-				now = os_nsecs();
-				if (now < nsecs)
-					break;
-				block_signals();
-				(*sig_info[sig])(sig, (struct siginfo *)&si, regs);
-				unblock_signals();
-				nsecs = timer.it_value.tv_sec *
-					UM_NSEC_PER_SEC +
-					timer.it_value.tv_usec *
-					UM_NSEC_PER_USEC;
-				nsecs += os_nsecs();
-				break;
+			case SIGALRM:
 			case SIGIO:
 			case SIGILL:
 			case SIGBUS:
@@ -487,8 +492,8 @@ __initcall(init_thread_regs);
 
 int copy_context_skas0(unsigned long new_stack, int pid)
 {
-	struct timeval tv = { .tv_sec = 0, .tv_usec = UM_USEC_PER_SEC / UM_HZ };
 	int err;
+	unsigned long remain;
 	unsigned long current_stack = current_stub_stack();
 	struct stub_data *data = (struct stub_data *) current_stack;
 	struct stub_data *child_data = (struct stub_data *) new_stack;
@@ -499,11 +504,19 @@ int copy_context_skas0(unsigned long new_stack, int pid)
 	 * prepare offset and fd of child's stack as argument for parent's
 	 * and child's mmap2 calls
 	 */
-	*data = ((struct stub_data) { .offset	= MMAP_OFFSET(new_offset),
-				      .fd	= new_fd,
-				      .timer    = ((struct itimerval)
-					           { .it_value = tv,
-						     .it_interval = tv }) });
+	remain = os_timer_remain(NULL);
+	if (remain == 0)
+		remain = UM_NSEC_PER_SEC / UM_HZ;
+
+	*data = ((struct stub_data) { 
+			.offset	= MMAP_OFFSET(new_offset),
+			.fd     = new_fd,
+			.timer  = ((struct itimerspec)
+					     { .it_value.tv_sec  = 0,
+					       .it_value.tv_nsec = remain,
+					       .it_interval.tv_sec  = 0,
+					       .it_interval.tv_nsec = UM_NSEC_PER_SEC / UM_HZ })
+	});
 
 	err = ptrace_setregs(pid, thread_regs);
 	if (err < 0) {
diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c
index e9824d5..0e2bb7d 100644
--- a/arch/um/os-Linux/time.c
+++ b/arch/um/os-Linux/time.c
@@ -1,4 +1,5 @@
 /*
+ * Copyright (C) 2012-2014 Cisco Systems
  * Copyright (C) 2000 - 2007 Jeff Dike (jdike{addtoit,linux.intel}.com)
  * Licensed under the GPL
  */
@@ -10,177 +11,172 @@
 #include <sys/time.h>
 #include <kern_util.h>
 #include <os.h>
-#include "internal.h"
+#include <string.h>
+#include <timer-internal.h>
 
-int set_interval(void)
-{
-	int usec = UM_USEC_PER_SEC / UM_HZ;
-	struct itimerval interval = ((struct itimerval) { { 0, usec },
-							  { 0, usec } });
-
-	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
-		return -errno;
+static timer_t event_high_res_timer = 0;
 
-	return 0;
+static inline long long timeval_to_ns(const struct timeval *tv)
+{
+	return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
+		tv->tv_usec * UM_NSEC_PER_USEC;
 }
 
-int timer_one_shot(int ticks)
+static inline long long timespec_to_ns(const struct timespec *ts)
 {
-	unsigned long usec = ticks * UM_USEC_PER_SEC / UM_HZ;
-	unsigned long sec = usec / UM_USEC_PER_SEC;
-	struct itimerval interval;
-
-	usec %= UM_USEC_PER_SEC;
-	interval = ((struct itimerval) { { 0, 0 }, { sec, usec } });
+	return ((long long) ts->tv_sec * UM_NSEC_PER_SEC) +
+		ts->tv_nsec;
+}
 
-	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
-		return -errno;
+long long os_persistent_clock_emulation (void) {
+	struct timespec realtime_tp;
 
-	return 0;
+	clock_gettime(CLOCK_REALTIME, &realtime_tp);
+	return timespec_to_ns(&realtime_tp);
 }
 
 /**
- * timeval_to_ns - Convert timeval to nanoseconds
- * @ts:		pointer to the timeval variable to be converted
- *
- * Returns the scalar nanosecond representation of the timeval
- * parameter.
- *
- * Ripped from linux/time.h because it's a kernel header, and thus
- * unusable from here.
+ * os_timer_create() - create an new posix (interval) timer
  */
-static inline long long timeval_to_ns(const struct timeval *tv)
-{
-	return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
-		tv->tv_usec * UM_NSEC_PER_USEC;
+int os_timer_create(void* timer) {
+
+	timer_t* t = timer;
+
+	if(t == NULL) {
+		t = &event_high_res_timer;
+	}
+
+	if (timer_create(
+		CLOCK_MONOTONIC,
+		NULL,
+		t) == -1) {
+		return -1;
+	}
+	return 0;
 }
 
-long long disable_timer(void)
+int os_timer_set_interval(void* timer, void* i)
 {
-	struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } });
-	long long remain, max = UM_NSEC_PER_SEC / UM_HZ;
+	struct itimerspec its;
+	unsigned long long nsec;
+	timer_t* t = timer;
+	struct itimerspec* its_in = i;
 
-	if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0)
-		printk(UM_KERN_ERR "disable_timer - setitimer failed, "
-		       "errno = %d\n", errno);
+	if(t == NULL) {
+		t = &event_high_res_timer;
+	}
 
-	remain = timeval_to_ns(&time.it_value);
-	if (remain > max)
-		remain = max;
+	nsec = UM_NSEC_PER_SEC / UM_HZ;
 
-	return remain;
-}
+	if(its_in != NULL) {
+		its.it_value.tv_sec = its_in->it_value.tv_sec;
+		its.it_value.tv_nsec = its_in->it_value.tv_nsec;
+	} else {
+		its.it_value.tv_sec = 0;
+		its.it_value.tv_nsec = nsec;
+	}
 
-long long os_nsecs(void)
-{
-	struct timeval tv;
+	its.it_interval.tv_sec = 0;
+	its.it_interval.tv_nsec = nsec;
 
-	gettimeofday(&tv, NULL);
-	return timeval_to_ns(&tv);
-}
+	if(timer_settime(*t, 0, &its, NULL) == -1) {
+		return -errno;
+	}
 
-#ifdef UML_CONFIG_NO_HZ_COMMON
-static int after_sleep_interval(struct timespec *ts)
-{
 	return 0;
 }
 
-static void deliver_alarm(void)
+/**
+ * os_timer_remain() - returns the remaining nano seconds of the given interval
+ *                     timer
+ * Because this is the remaining time of an interval timer, which correspondends
+ * to HZ, this value can never be bigger than one second. Just
+ * the nanosecond part of the timer is returned.
+ * The returned time is relative to the start time of the interval timer.
+ * Return an negative value in an error case.
+ */
+long os_timer_remain(void* timer)
 {
-	alarm_handler(SIGVTALRM, NULL, NULL);
-}
+	struct itimerspec its;
+	timer_t* t = timer;
 
-static unsigned long long sleep_time(unsigned long long nsecs)
-{
-	return nsecs;
-}
+	if(t == NULL) {
+		t = &event_high_res_timer;
+	}
 
-#else
-unsigned long long last_tick;
-unsigned long long skew;
+	if(timer_gettime(t, &its) == -1) {
+		return -errno;
+	}
+
+	return its.it_value.tv_nsec;
+}
 
-static void deliver_alarm(void)
+int os_timer_one_shot(int ticks)
 {
-	unsigned long long this_tick = os_nsecs();
-	int one_tick = UM_NSEC_PER_SEC / UM_HZ;
+	struct itimerspec its;
+	unsigned long long nsec;
+	unsigned long sec;
 
-	/* Protection against the host's time going backwards */
-	if ((last_tick != 0) && (this_tick < last_tick))
-		this_tick = last_tick;
+    nsec = (ticks + 1);
+    sec = nsec / UM_NSEC_PER_SEC;
+	nsec = nsec % UM_NSEC_PER_SEC;
 
-	if (last_tick == 0)
-		last_tick = this_tick - one_tick;
+	its.it_value.tv_sec = nsec / UM_NSEC_PER_SEC;
+	its.it_value.tv_nsec = nsec;
 
-	skew += this_tick - last_tick;
+	its.it_interval.tv_sec = 0;
+	its.it_interval.tv_nsec = 0; // we cheat here
 
-	while (skew >= one_tick) {
-		alarm_handler(SIGVTALRM, NULL, NULL);
-		skew -= one_tick;
-	}
-
-	last_tick = this_tick;
+	timer_settime(event_high_res_timer, 0, &its, NULL);
+	return 0;
 }
 
-static unsigned long long sleep_time(unsigned long long nsecs)
+/**
+ * os_timer_disable() - disable the posix (interval) timer
+ * Returns the remaining interval timer time in nanoseconds
+ */
+long long os_timer_disable(void)
 {
-	return nsecs > skew ? nsecs - skew : 0;
+	struct itimerspec its;
+
+	memset(&its, 0, sizeof(struct itimerspec));
+	timer_settime(event_high_res_timer, 0, &its, &its);
+
+	return its.it_value.tv_sec * UM_NSEC_PER_SEC + its.it_value.tv_nsec;
 }
 
-static inline long long timespec_to_us(const struct timespec *ts)
+long long os_vnsecs(void)
 {
-	return ((long long) ts->tv_sec * UM_USEC_PER_SEC) +
-		ts->tv_nsec / UM_NSEC_PER_USEC;
+	struct timespec ts;
+
+	clock_gettime(CLOCK_PROCESS_CPUTIME_ID,&ts);
+	return timespec_to_ns(&ts);
 }
 
-static int after_sleep_interval(struct timespec *ts)
+long long os_nsecs(void)
 {
-	int usec = UM_USEC_PER_SEC / UM_HZ;
-	long long start_usecs = timespec_to_us(ts);
-	struct timeval tv;
-	struct itimerval interval;
-
-	/*
-	 * It seems that rounding can increase the value returned from
-	 * setitimer to larger than the one passed in.  Over time,
-	 * this will cause the remaining time to be greater than the
-	 * tick interval.  If this happens, then just reduce the first
-	 * tick to the interval value.
-	 */
-	if (start_usecs > usec)
-		start_usecs = usec;
-
-	start_usecs -= skew / UM_NSEC_PER_USEC;
-	if (start_usecs < 0)
-		start_usecs = 0;
-
-	tv = ((struct timeval) { .tv_sec  = start_usecs / UM_USEC_PER_SEC,
-				 .tv_usec = start_usecs % UM_USEC_PER_SEC });
-	interval = ((struct itimerval) { { 0, usec }, tv });
-
-	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
-		return -errno;
+	struct timespec ts;
 
-	return 0;
+	clock_gettime(CLOCK_MONOTONIC,&ts);
+	return timespec_to_ns(&ts);
 }
-#endif
 
-void idle_sleep(unsigned long long nsecs)
+/**
+ * os_idle_sleep() - sleep for a given time of nsecs
+ * @nsecs: nanoseconds to sleep
+ */
+void os_idle_sleep(unsigned long long nsecs)
 {
 	struct timespec ts;
 
-	/*
-	 * nsecs can come in as zero, in which case, this starts a
-	 * busy loop.  To prevent this, reset nsecs to the tick
-	 * interval if it is zero.
-	 */
-	if (nsecs == 0)
-		nsecs = UM_NSEC_PER_SEC / UM_HZ;
-
-	nsecs = sleep_time(nsecs);
-	ts = ((struct timespec) { .tv_sec	= nsecs / UM_NSEC_PER_SEC,
-				  .tv_nsec	= nsecs % UM_NSEC_PER_SEC });
-
-	if (nanosleep(&ts, &ts) == 0)
-		deliver_alarm();
-	after_sleep_interval(&ts);
+	if (nsecs <= 0) {
+		return;
+	}
+
+	ts = ((struct timespec) {
+			.tv_sec  = nsecs / UM_NSEC_PER_SEC,
+			.tv_nsec = nsecs % UM_NSEC_PER_SEC
+	});
+
+	clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, NULL);
 }




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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Anton Ivanov]

Same story.

Overall works quite well, the moment I give it the "dselect upgrade 
test" the userspace hangs.

Kernel continues to work - forwarding, icmp, uml_mconsole are fine.

A.

On 17/05/15 10:25, Thomas Meyer wrote:
> Switch the UML clocksource from interval timers to posix interval timers
> and move to a monotonic timer.
>
> This fixes suspend&resume related timer issues and improves network
> performance as TCP state machines are now fed with the correct time;
> also correct QoS and traffic shaping.
>
> Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
> ---
>
> diff --git a/arch/um/Makefile b/arch/um/Makefile
> index e4b1a96..43ef190 100644
> --- a/arch/um/Makefile
> +++ b/arch/um/Makefile
> @@ -130,7 +130,7 @@ export LDS_ELF_FORMAT := $(ELF_FORMAT)
>   # The wrappers will select whether using "malloc" or the kernel allocator.
>   LINK_WRAPS = -Wl,--wrap,malloc -Wl,--wrap,free -Wl,--wrap,calloc
>   
> -LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt))
> +LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt)) -lrt
>   
>   # Used by link-vmlinux.sh which has special support for um link
>   export CFLAGS_vmlinux := $(LINK-y) $(LINK_WRAPS) $(LD_FLAGS_CMDLINE)
> diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
> index 08eec0b..5949cae 100644
> --- a/arch/um/include/shared/os.h
> +++ b/arch/um/include/shared/os.h
> @@ -219,7 +219,7 @@ extern int set_umid(char *name);
>   extern char *get_umid(void);
>   
>   /* signal.c */
> -extern void timer_init(void);
> +extern void timer_set_signal_handler(void);
>   extern void set_sigstack(void *sig_stack, int size);
>   extern void remove_sigstack(void);
>   extern void set_handler(int sig);
> @@ -240,12 +240,16 @@ extern void um_early_printk(const char *s, unsigned int n);
>   extern void os_fix_helper_signals(void);
>   
>   /* time.c */
> -extern void idle_sleep(unsigned long long nsecs);
> -extern int set_interval(void);
> -extern int timer_one_shot(int ticks);
> -extern long long disable_timer(void);
> +extern void os_idle_sleep(unsigned long long nsecs);
> +extern int os_timer_create(void* timer);
> +extern int os_timer_set_interval(void* timer, void* its);
> +extern int os_timer_one_shot(int ticks);
> +extern long long os_timer_disable(void);
> +extern long os_timer_remain(void* timer);
>   extern void uml_idle_timer(void);
> +extern long long os_persistent_clock_emulation(void);
>   extern long long os_nsecs(void);
> +extern long long os_vnsecs(void);
>   
>   /* skas/mem.c */
>   extern long run_syscall_stub(struct mm_id * mm_idp,
> diff --git a/arch/um/include/shared/skas/stub-data.h b/arch/um/include/shared/skas/stub-data.h
> index f6ed92c..f98b9e2 100644
> --- a/arch/um/include/shared/skas/stub-data.h
> +++ b/arch/um/include/shared/skas/stub-data.h
> @@ -6,12 +6,12 @@
>   #ifndef __STUB_DATA_H
>   #define __STUB_DATA_H
>   
> -#include <sys/time.h>
> +#include <time.h>
>   
>   struct stub_data {
> -	long offset;
> +	unsigned long offset;
>   	int fd;
> -	struct itimerval timer;
> +	struct itimerspec timer;
>   	long err;
>   };
>   
> diff --git a/arch/um/include/shared/timer-internal.h b/arch/um/include/shared/timer-internal.h
> new file mode 100644
> index 0000000..03e6f21
> --- /dev/null
> +++ b/arch/um/include/shared/timer-internal.h
> @@ -0,0 +1,13 @@
> +/*
> + * Copyright (C) 2012 - 2014 Cisco Systems
> + * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
> + * Licensed under the GPL
> + */
> +
> +#ifndef __TIMER_INTERNAL_H__
> +#define __TIMER_INTERNAL_H__
> +
> +#define TIMER_MULTIPLIER 256
> +#define TIMER_MIN_DELTA  500
> +
> +#endif
> diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
> index f17bca8..d0bbd01 100644
> --- a/arch/um/kernel/process.c
> +++ b/arch/um/kernel/process.c
> @@ -27,6 +27,7 @@
>   #include <kern_util.h>
>   #include <os.h>
>   #include <skas.h>
> +#include <timer-internal.h>
>   
>   /*
>    * This is a per-cpu array.  A processor only modifies its entry and it only
> @@ -201,11 +202,8 @@ void initial_thread_cb(void (*proc)(void *), void *arg)
>   
>   void arch_cpu_idle(void)
>   {
> -	unsigned long long nsecs;
> -
>   	cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
> -	nsecs = disable_timer();
> -	idle_sleep(nsecs);
> +	os_idle_sleep(UM_NSEC_PER_SEC / UM_HZ);
>   	local_irq_enable();
>   }
>   
> diff --git a/arch/um/kernel/skas/clone.c b/arch/um/kernel/skas/clone.c
> index 289771d..814ec8b 100644
> --- a/arch/um/kernel/skas/clone.c
> +++ b/arch/um/kernel/skas/clone.c
> @@ -24,6 +24,7 @@ void __attribute__ ((__section__ (".__syscall_stub")))
>   stub_clone_handler(void)
>   {
>   	struct stub_data *data = (struct stub_data *) STUB_DATA;
> +	timer_t timerid;
>   	long err;
>   
>   	err = stub_syscall2(__NR_clone, CLONE_PARENT | CLONE_FILES | SIGCHLD,
> @@ -35,8 +36,14 @@ stub_clone_handler(void)
>   	if (err)
>   		goto out;
>   
> -	err = stub_syscall3(__NR_setitimer, ITIMER_VIRTUAL,
> -			    (long) &data->timer, 0);
> +	/* create posix interval timer */
> +	err = stub_syscall3(__NR_timer_create, CLOCK_MONOTONIC, 0l, (long) &timerid);
> +	if (err)
> +		goto out;
> +
> +	/* set interval to the given value from copy_context_skas0() */
> +	err = stub_syscall4(__NR_timer_settime, (long) timerid, 0l,
> +						(long) &data->timer, 0l);
>   	if (err)
>   		goto out;
>   
> diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c
> index 117568d..d15966c 100644
> --- a/arch/um/kernel/time.c
> +++ b/arch/um/kernel/time.c
> @@ -1,4 +1,5 @@
>   /*
> + * Copyright (C) 2012-2014 Cisco Systems
>    * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
>    * Licensed under the GPL
>    */
> @@ -8,10 +9,12 @@
>   #include <linux/interrupt.h>
>   #include <linux/jiffies.h>
>   #include <linux/threads.h>
> +#include <linux/spinlock.h>
>   #include <asm/irq.h>
>   #include <asm/param.h>
>   #include <kern_util.h>
>   #include <os.h>
> +#include <timer-internal.h>
>   
>   void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
>   {
> @@ -22,18 +25,20 @@ void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
>   	local_irq_restore(flags);
>   }
>   
> -static void itimer_set_mode(enum clock_event_mode mode,
> +static void timer_set_mode(enum clock_event_mode mode,
>   			    struct clock_event_device *evt)
>   {
>   	switch (mode) {
>   	case CLOCK_EVT_MODE_PERIODIC:
> -		set_interval();
> +		os_timer_set_interval(NULL, NULL);
>   		break;
>   
> +	case CLOCK_EVT_MODE_ONESHOT:
> +		os_timer_one_shot(1);
> +
>   	case CLOCK_EVT_MODE_SHUTDOWN:
>   	case CLOCK_EVT_MODE_UNUSED:
> -	case CLOCK_EVT_MODE_ONESHOT:
> -		disable_timer();
> +		os_timer_disable();
>   		break;
>   
>   	case CLOCK_EVT_MODE_RESUME:
> @@ -41,68 +46,74 @@ static void itimer_set_mode(enum clock_event_mode mode,
>   	}
>   }
>   
> -static int itimer_next_event(unsigned long delta,
> +static int timer_next_event(unsigned long delta,
>   			     struct clock_event_device *evt)
>   {
> -	return timer_one_shot(delta + 1);
> +	return os_timer_one_shot(delta);
>   }
>   
> -static struct clock_event_device itimer_clockevent = {
> -	.name		= "itimer",
> +static struct clock_event_device timer_clockevent = {
> +	.name		= "posix-timer",
>   	.rating		= 250,
>   	.cpumask	= cpu_all_mask,
>   	.features	= CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
> -	.set_mode	= itimer_set_mode,
> -	.set_next_event = itimer_next_event,
> -	.shift		= 32,
> +	.set_mode	= timer_set_mode,
> +	.set_next_event = timer_next_event,
> +	.shift		= 0,
> +	.max_delta_ns	= 0xffffffff,
> +	.min_delta_ns	= TIMER_MIN_DELTA, //microsecond resolution should be enough for anyone, same as 640K RAM
>   	.irq		= 0,
> +	.mult		= 1,
>   };
>   
> -static irqreturn_t um_timer(int irq, void *dev)
> +static irqreturn_t um_timer_irq(int irq, void *dev)
>   {
> -	(*itimer_clockevent.event_handler)(&itimer_clockevent);
> +	(*timer_clockevent.event_handler)(&timer_clockevent);
>   
>   	return IRQ_HANDLED;
>   }
>   
> -static cycle_t itimer_read(struct clocksource *cs)
> +static cycle_t timer_read(struct clocksource *cs)
>   {
> -	return os_nsecs() / 1000;
> +	return os_nsecs() / TIMER_MULTIPLIER;
>   }
>   
> -static struct clocksource itimer_clocksource = {
> -	.name		= "itimer",
> +static struct clocksource timer_clocksource = {
> +	.name		= "timer",
>   	.rating		= 300,
> -	.read		= itimer_read,
> +	.read		= timer_read,
>   	.mask		= CLOCKSOURCE_MASK(64),
>   	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
>   };
>   
> -static void __init setup_itimer(void)
> +static void __init timer_setup(void)
>   {
>   	int err;
>   
> -	err = request_irq(TIMER_IRQ, um_timer, 0, "timer", NULL);
> -	if (err != 0)
> +	err = request_irq(TIMER_IRQ, um_timer_irq, IRQF_TIMER, "hr timer", NULL);
> +	if (err != 0) {
>   		printk(KERN_ERR "register_timer : request_irq failed - "
>   		       "errno = %d\n", -err);
> +		return;
> +    }
> +
> +    err = os_timer_create(NULL);
> +    if (err != 0) {
> +        printk(KERN_ERR "creation of timer failed - errno = %d\n", -err);
> +        return;
> +    }
>   
> -	itimer_clockevent.mult = div_sc(HZ, NSEC_PER_SEC, 32);
> -	itimer_clockevent.max_delta_ns =
> -		clockevent_delta2ns(60 * HZ, &itimer_clockevent);
> -	itimer_clockevent.min_delta_ns =
> -		clockevent_delta2ns(1, &itimer_clockevent);
> -	err = clocksource_register_hz(&itimer_clocksource, USEC_PER_SEC);
> +	err = clocksource_register_hz(&timer_clocksource, NSEC_PER_SEC/TIMER_MULTIPLIER);
>   	if (err) {
>   		printk(KERN_ERR "clocksource_register_hz returned %d\n", err);
>   		return;
>   	}
> -	clockevents_register_device(&itimer_clockevent);
> +	clockevents_register_device(&timer_clockevent);
>   }
>   
>   void read_persistent_clock(struct timespec *ts)
>   {
> -	long long nsecs = os_nsecs();
> +	long long nsecs = os_persistent_clock_emulation();
>   
>   	set_normalized_timespec(ts, nsecs / NSEC_PER_SEC,
>   				nsecs % NSEC_PER_SEC);
> @@ -110,6 +121,6 @@ void read_persistent_clock(struct timespec *ts)
>   
>   void __init time_init(void)
>   {
> -	timer_init();
> -	late_time_init = setup_itimer;
> +	timer_set_signal_handler();
> +	late_time_init = timer_setup;
>   }
> diff --git a/arch/um/os-Linux/internal.h b/arch/um/os-Linux/internal.h
> deleted file mode 100644
> index 0dc2c9f..0000000
> --- a/arch/um/os-Linux/internal.h
> +++ /dev/null
> @@ -1 +0,0 @@
> -void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc);
> diff --git a/arch/um/os-Linux/main.c b/arch/um/os-Linux/main.c
> index df9191a..6e36f0f 100644
> --- a/arch/um/os-Linux/main.c
> +++ b/arch/um/os-Linux/main.c
> @@ -163,13 +163,13 @@ int __init main(int argc, char **argv, char **envp)
>   
>   	/*
>   	 * This signal stuff used to be in the reboot case.  However,
> -	 * sometimes a SIGVTALRM can come in when we're halting (reproducably
> +	 * sometimes a timer signal can come in when we're halting (reproducably
>   	 * when writing out gcov information, presumably because that takes
>   	 * some time) and cause a segfault.
>   	 */
>   
> -	/* stop timers and set SIGVTALRM to be ignored */
> -	disable_timer();
> +	/* stop timers and set timer signal to be ignored */
> +	os_timer_disable();
>   
>   	/* disable SIGIO for the fds and set SIGIO to be ignored */
>   	err = deactivate_all_fds();
> diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
> index 7b605e4..4a9be55 100644
> --- a/arch/um/os-Linux/signal.c
> +++ b/arch/um/os-Linux/signal.c
> @@ -13,7 +13,6 @@
>   #include <kern_util.h>
>   #include <os.h>
>   #include <sysdep/mcontext.h>
> -#include "internal.h"
>   
>   void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
>   	[SIGTRAP]	= relay_signal,
> @@ -23,7 +22,8 @@ void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
>   	[SIGBUS]	= bus_handler,
>   	[SIGSEGV]	= segv_handler,
>   	[SIGIO]		= sigio_handler,
> -	[SIGVTALRM]	= timer_handler };
> +	[SIGALRM]	= timer_handler
> +};
>   
>   static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
>   {
> @@ -38,7 +38,7 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
>   	}
>   
>   	/* enable signals if sig isn't IRQ signal */
> -	if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGVTALRM))
> +	if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGALRM))
>   		unblock_signals();
>   
>   	(*sig_info[sig])(sig, si, &r);
> @@ -55,8 +55,8 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
>   #define SIGIO_BIT 0
>   #define SIGIO_MASK (1 << SIGIO_BIT)
>   
> -#define SIGVTALRM_BIT 1
> -#define SIGVTALRM_MASK (1 << SIGVTALRM_BIT)
> +#define SIGALRM_BIT 1
> +#define SIGALRM_MASK (1 << SIGALRM_BIT)
>   
>   static int signals_enabled;
>   static unsigned int signals_pending;
> @@ -78,46 +78,47 @@ void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
>   	set_signals(enabled);
>   }
>   
> -static void real_alarm_handler(mcontext_t *mc)
> +static void timer_real_alarm_handler(mcontext_t *mc)
>   {
>   	struct uml_pt_regs regs;
>   
>   	if (mc != NULL)
>   		get_regs_from_mc(&regs, mc);
>   	regs.is_user = 0;
> -	unblock_signals();
> -	timer_handler(SIGVTALRM, NULL, &regs);
> +	timer_handler(SIGALRM, NULL, &regs);
>   }
>   
> -void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
> +void timer_alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
>   {
>   	int enabled;
>   
>   	enabled = signals_enabled;
>   	if (!signals_enabled) {
> -		signals_pending |= SIGVTALRM_MASK;
> +		signals_pending |= SIGALRM_MASK;
>   		return;
>   	}
>   
>   	block_signals();
> -
> -	real_alarm_handler(mc);
> +	timer_real_alarm_handler(mc);
>   	set_signals(enabled);
>   }
>   
> -void timer_init(void)
> +void timer_set_signal_handler(void)
>   {
> -	set_handler(SIGVTALRM);
> +	set_handler(SIGALRM);
>   }
>   
>   void set_sigstack(void *sig_stack, int size)
>   {
> -	stack_t stack = ((stack_t) { .ss_flags	= 0,
> -				     .ss_sp	= (__ptr_t) sig_stack,
> -				     .ss_size 	= size - sizeof(void *) });
> +	stack_t stack = ((stack_t) {
> +	            .ss_flags = 0,
> +				.ss_sp    = (__ptr_t) sig_stack,
> +				.ss_size  = size - sizeof(void *)
> +	});
>   
> -	if (sigaltstack(&stack, NULL) != 0)
> +	if (sigaltstack(&stack, NULL) != 0) {
>   		panic("enabling signal stack failed, errno = %d\n", errno);
> +	}
>   }
>   
>   static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
> @@ -129,10 +130,9 @@ static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
>   
>   	[SIGIO] = sig_handler,
>   	[SIGWINCH] = sig_handler,
> -	[SIGVTALRM] = alarm_handler
> +	[SIGALRM] = timer_alarm_handler
>   };
>   
> -
>   static void hard_handler(int sig, siginfo_t *si, void *p)
>   {
>   	struct ucontext *uc = p;
> @@ -186,9 +186,9 @@ void set_handler(int sig)
>   
>   	/* block irq ones */
>   	sigemptyset(&action.sa_mask);
> -	sigaddset(&action.sa_mask, SIGVTALRM);
>   	sigaddset(&action.sa_mask, SIGIO);
>   	sigaddset(&action.sa_mask, SIGWINCH);
> +	sigaddset(&action.sa_mask, SIGALRM);
>   
>   	if (sig == SIGSEGV)
>   		flags |= SA_NODEFER;
> @@ -281,8 +281,8 @@ void unblock_signals(void)
>   		if (save_pending & SIGIO_MASK)
>   			sig_handler_common(SIGIO, NULL, NULL);
>   
> -		if (save_pending & SIGVTALRM_MASK)
> -			real_alarm_handler(NULL);
> +		if (save_pending & SIGALRM_MASK)
> +			timer_real_alarm_handler(NULL);
>   	}
>   }
>   
> diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
> index 908579f..f669f9d 100644
> --- a/arch/um/os-Linux/skas/process.c
> +++ b/arch/um/os-Linux/skas/process.c
> @@ -47,7 +47,7 @@ static int ptrace_dump_regs(int pid)
>    * Signals that are OK to receive in the stub - we'll just continue it.
>    * SIGWINCH will happen when UML is inside a detached screen.
>    */
> -#define STUB_SIG_MASK ((1 << SIGVTALRM) | (1 << SIGWINCH))
> +#define STUB_SIG_MASK ((1 << SIGALRM) | (1 << SIGWINCH))
>   
>   /* Signals that the stub will finish with - anything else is an error */
>   #define STUB_DONE_MASK (1 << SIGTRAP)
> @@ -199,12 +199,23 @@ static int userspace_tramp(void *stack)
>   {
>   	void *addr;
>   	int err;
> +	timer_t timer;
> +
> +	struct stub_data *data = (struct stub_data *) stack;
>   
>   	ptrace(PTRACE_TRACEME, 0, 0, 0);
>   
>   	signal(SIGTERM, SIG_DFL);
>   	signal(SIGWINCH, SIG_IGN);
> -	err = set_interval();
> +
> +	err = os_timer_create(&timer);
> +	if (err) {
> +		printk(UM_KERN_ERR "userspace_tramp - creation of timer failed, "
> +		       "errno = %d\n", err);
> +		exit(1);
> +	}
> +
> +	err = os_timer_set_interval(&timer, &data->timer);
>   	if (err) {
>   		printk(UM_KERN_ERR "userspace_tramp - setting timer failed, "
>   		       "errno = %d\n", err);
> @@ -271,8 +282,9 @@ int userspace_pid[NR_CPUS];
>   int start_userspace(unsigned long stub_stack)
>   {
>   	void *stack;
> -	unsigned long sp;
> +	unsigned long sp, remain;
>   	int pid, status, n, flags, err;
> +	struct stub_data *data = (struct stub_data *) stub_stack;
>   
>   	stack = mmap(NULL, UM_KERN_PAGE_SIZE,
>   		     PROT_READ | PROT_WRITE | PROT_EXEC,
> @@ -292,6 +304,18 @@ int start_userspace(unsigned long stub_stack)
>   	else
>   		flags |= SIGCHLD;
>   
> +	remain = os_timer_remain(NULL);
> +	if (remain == 0)
> +		remain = UM_NSEC_PER_SEC / UM_HZ;
> +
> +	*data = ((struct stub_data) {
> +			.timer  = ((struct itimerspec)
> +				{ .it_value.tv_sec  = 0,
> +				  .it_value.tv_nsec = remain,
> +				  .it_interval.tv_sec  = 0,
> +				  .it_interval.tv_nsec = UM_NSEC_PER_SEC / UM_HZ })
> +	});
> +
>   	pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
>   	if (pid < 0) {
>   		err = -errno;
> @@ -308,7 +332,7 @@ int start_userspace(unsigned long stub_stack)
>   			       "errno = %d\n", errno);
>   			goto out_kill;
>   		}
> -	} while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGVTALRM));
> +	} while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGALRM));
>   
>   	if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
>   		err = -EINVAL;
> @@ -341,8 +365,6 @@ int start_userspace(unsigned long stub_stack)
>   
>   void userspace(struct uml_pt_regs *regs)
>   {
> -	struct itimerval timer;
> -	unsigned long long nsecs, now;
>   	int err, status, op, pid = userspace_pid[0];
>   	/* To prevent races if using_sysemu changes under us.*/
>   	int local_using_sysemu;
> @@ -351,13 +373,8 @@ void userspace(struct uml_pt_regs *regs)
>   	/* Handle any immediate reschedules or signals */
>   	interrupt_end();
>   
> -	if (getitimer(ITIMER_VIRTUAL, &timer))
> -		printk(UM_KERN_ERR "Failed to get itimer, errno = %d\n", errno);
> -	nsecs = timer.it_value.tv_sec * UM_NSEC_PER_SEC +
> -		timer.it_value.tv_usec * UM_NSEC_PER_USEC;
> -	nsecs += os_nsecs();
> -
>   	while (1) {
> +
>   		/*
>   		 * This can legitimately fail if the process loads a
>   		 * bogus value into a segment register.  It will
> @@ -428,19 +445,7 @@ void userspace(struct uml_pt_regs *regs)
>   			case SIGTRAP:
>   				relay_signal(SIGTRAP, (struct siginfo *)&si, regs);
>   				break;
> -			case SIGVTALRM:
> -				now = os_nsecs();
> -				if (now < nsecs)
> -					break;
> -				block_signals();
> -				(*sig_info[sig])(sig, (struct siginfo *)&si, regs);
> -				unblock_signals();
> -				nsecs = timer.it_value.tv_sec *
> -					UM_NSEC_PER_SEC +
> -					timer.it_value.tv_usec *
> -					UM_NSEC_PER_USEC;
> -				nsecs += os_nsecs();
> -				break;
> +			case SIGALRM:
>   			case SIGIO:
>   			case SIGILL:
>   			case SIGBUS:
> @@ -487,8 +492,8 @@ __initcall(init_thread_regs);
>   
>   int copy_context_skas0(unsigned long new_stack, int pid)
>   {
> -	struct timeval tv = { .tv_sec = 0, .tv_usec = UM_USEC_PER_SEC / UM_HZ };
>   	int err;
> +	unsigned long remain;
>   	unsigned long current_stack = current_stub_stack();
>   	struct stub_data *data = (struct stub_data *) current_stack;
>   	struct stub_data *child_data = (struct stub_data *) new_stack;
> @@ -499,11 +504,19 @@ int copy_context_skas0(unsigned long new_stack, int pid)
>   	 * prepare offset and fd of child's stack as argument for parent's
>   	 * and child's mmap2 calls
>   	 */
> -	*data = ((struct stub_data) { .offset	= MMAP_OFFSET(new_offset),
> -				      .fd	= new_fd,
> -				      .timer    = ((struct itimerval)
> -					           { .it_value = tv,
> -						     .it_interval = tv }) });
> +	remain = os_timer_remain(NULL);
> +	if (remain == 0)
> +		remain = UM_NSEC_PER_SEC / UM_HZ;
> +
> +	*data = ((struct stub_data) {
> +			.offset	= MMAP_OFFSET(new_offset),
> +			.fd     = new_fd,
> +			.timer  = ((struct itimerspec)
> +					     { .it_value.tv_sec  = 0,
> +					       .it_value.tv_nsec = remain,
> +					       .it_interval.tv_sec  = 0,
> +					       .it_interval.tv_nsec = UM_NSEC_PER_SEC / UM_HZ })
> +	});
>   
>   	err = ptrace_setregs(pid, thread_regs);
>   	if (err < 0) {
> diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c
> index e9824d5..0e2bb7d 100644
> --- a/arch/um/os-Linux/time.c
> +++ b/arch/um/os-Linux/time.c
> @@ -1,4 +1,5 @@
>   /*
> + * Copyright (C) 2012-2014 Cisco Systems
>    * Copyright (C) 2000 - 2007 Jeff Dike (jdike{addtoit,linux.intel}.com)
>    * Licensed under the GPL
>    */
> @@ -10,177 +11,172 @@
>   #include <sys/time.h>
>   #include <kern_util.h>
>   #include <os.h>
> -#include "internal.h"
> +#include <string.h>
> +#include <timer-internal.h>
>   
> -int set_interval(void)
> -{
> -	int usec = UM_USEC_PER_SEC / UM_HZ;
> -	struct itimerval interval = ((struct itimerval) { { 0, usec },
> -							  { 0, usec } });
> -
> -	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
> -		return -errno;
> +static timer_t event_high_res_timer = 0;
>   
> -	return 0;
> +static inline long long timeval_to_ns(const struct timeval *tv)
> +{
> +	return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
> +		tv->tv_usec * UM_NSEC_PER_USEC;
>   }
>   
> -int timer_one_shot(int ticks)
> +static inline long long timespec_to_ns(const struct timespec *ts)
>   {
> -	unsigned long usec = ticks * UM_USEC_PER_SEC / UM_HZ;
> -	unsigned long sec = usec / UM_USEC_PER_SEC;
> -	struct itimerval interval;
> -
> -	usec %= UM_USEC_PER_SEC;
> -	interval = ((struct itimerval) { { 0, 0 }, { sec, usec } });
> +	return ((long long) ts->tv_sec * UM_NSEC_PER_SEC) +
> +		ts->tv_nsec;
> +}
>   
> -	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
> -		return -errno;
> +long long os_persistent_clock_emulation (void) {
> +	struct timespec realtime_tp;
>   
> -	return 0;
> +	clock_gettime(CLOCK_REALTIME, &realtime_tp);
> +	return timespec_to_ns(&realtime_tp);
>   }
>   
>   /**
> - * timeval_to_ns - Convert timeval to nanoseconds
> - * @ts:		pointer to the timeval variable to be converted
> - *
> - * Returns the scalar nanosecond representation of the timeval
> - * parameter.
> - *
> - * Ripped from linux/time.h because it's a kernel header, and thus
> - * unusable from here.
> + * os_timer_create() - create an new posix (interval) timer
>    */
> -static inline long long timeval_to_ns(const struct timeval *tv)
> -{
> -	return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
> -		tv->tv_usec * UM_NSEC_PER_USEC;
> +int os_timer_create(void* timer) {
> +
> +	timer_t* t = timer;
> +
> +	if(t == NULL) {
> +		t = &event_high_res_timer;
> +	}
> +
> +	if (timer_create(
> +		CLOCK_MONOTONIC,
> +		NULL,
> +		t) == -1) {
> +		return -1;
> +	}
> +	return 0;
>   }
>   
> -long long disable_timer(void)
> +int os_timer_set_interval(void* timer, void* i)
>   {
> -	struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } });
> -	long long remain, max = UM_NSEC_PER_SEC / UM_HZ;
> +	struct itimerspec its;
> +	unsigned long long nsec;
> +	timer_t* t = timer;
> +	struct itimerspec* its_in = i;
>   
> -	if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0)
> -		printk(UM_KERN_ERR "disable_timer - setitimer failed, "
> -		       "errno = %d\n", errno);
> +	if(t == NULL) {
> +		t = &event_high_res_timer;
> +	}
>   
> -	remain = timeval_to_ns(&time.it_value);
> -	if (remain > max)
> -		remain = max;
> +	nsec = UM_NSEC_PER_SEC / UM_HZ;
>   
> -	return remain;
> -}
> +	if(its_in != NULL) {
> +		its.it_value.tv_sec = its_in->it_value.tv_sec;
> +		its.it_value.tv_nsec = its_in->it_value.tv_nsec;
> +	} else {
> +		its.it_value.tv_sec = 0;
> +		its.it_value.tv_nsec = nsec;
> +	}
>   
> -long long os_nsecs(void)
> -{
> -	struct timeval tv;
> +	its.it_interval.tv_sec = 0;
> +	its.it_interval.tv_nsec = nsec;
>   
> -	gettimeofday(&tv, NULL);
> -	return timeval_to_ns(&tv);
> -}
> +	if(timer_settime(*t, 0, &its, NULL) == -1) {
> +		return -errno;
> +	}
>   
> -#ifdef UML_CONFIG_NO_HZ_COMMON
> -static int after_sleep_interval(struct timespec *ts)
> -{
>   	return 0;
>   }
>   
> -static void deliver_alarm(void)
> +/**
> + * os_timer_remain() - returns the remaining nano seconds of the given interval
> + *                     timer
> + * Because this is the remaining time of an interval timer, which correspondends
> + * to HZ, this value can never be bigger than one second. Just
> + * the nanosecond part of the timer is returned.
> + * The returned time is relative to the start time of the interval timer.
> + * Return an negative value in an error case.
> + */
> +long os_timer_remain(void* timer)
>   {
> -	alarm_handler(SIGVTALRM, NULL, NULL);
> -}
> +	struct itimerspec its;
> +	timer_t* t = timer;
>   
> -static unsigned long long sleep_time(unsigned long long nsecs)
> -{
> -	return nsecs;
> -}
> +	if(t == NULL) {
> +		t = &event_high_res_timer;
> +	}
>   
> -#else
> -unsigned long long last_tick;
> -unsigned long long skew;
> +	if(timer_gettime(t, &its) == -1) {
> +		return -errno;
> +	}
> +
> +	return its.it_value.tv_nsec;
> +}
>   
> -static void deliver_alarm(void)
> +int os_timer_one_shot(int ticks)
>   {
> -	unsigned long long this_tick = os_nsecs();
> -	int one_tick = UM_NSEC_PER_SEC / UM_HZ;
> +	struct itimerspec its;
> +	unsigned long long nsec;
> +	unsigned long sec;
>   
> -	/* Protection against the host's time going backwards */
> -	if ((last_tick != 0) && (this_tick < last_tick))
> -		this_tick = last_tick;
> +    nsec = (ticks + 1);
> +    sec = nsec / UM_NSEC_PER_SEC;
> +	nsec = nsec % UM_NSEC_PER_SEC;
>   
> -	if (last_tick == 0)
> -		last_tick = this_tick - one_tick;
> +	its.it_value.tv_sec = nsec / UM_NSEC_PER_SEC;
> +	its.it_value.tv_nsec = nsec;
>   
> -	skew += this_tick - last_tick;
> +	its.it_interval.tv_sec = 0;
> +	its.it_interval.tv_nsec = 0; // we cheat here
>   
> -	while (skew >= one_tick) {
> -		alarm_handler(SIGVTALRM, NULL, NULL);
> -		skew -= one_tick;
> -	}
> -
> -	last_tick = this_tick;
> +	timer_settime(event_high_res_timer, 0, &its, NULL);
> +	return 0;
>   }
>   
> -static unsigned long long sleep_time(unsigned long long nsecs)
> +/**
> + * os_timer_disable() - disable the posix (interval) timer
> + * Returns the remaining interval timer time in nanoseconds
> + */
> +long long os_timer_disable(void)
>   {
> -	return nsecs > skew ? nsecs - skew : 0;
> +	struct itimerspec its;
> +
> +	memset(&its, 0, sizeof(struct itimerspec));
> +	timer_settime(event_high_res_timer, 0, &its, &its);
> +
> +	return its.it_value.tv_sec * UM_NSEC_PER_SEC + its.it_value.tv_nsec;
>   }
>   
> -static inline long long timespec_to_us(const struct timespec *ts)
> +long long os_vnsecs(void)
>   {
> -	return ((long long) ts->tv_sec * UM_USEC_PER_SEC) +
> -		ts->tv_nsec / UM_NSEC_PER_USEC;
> +	struct timespec ts;
> +
> +	clock_gettime(CLOCK_PROCESS_CPUTIME_ID,&ts);
> +	return timespec_to_ns(&ts);
>   }
>   
> -static int after_sleep_interval(struct timespec *ts)
> +long long os_nsecs(void)
>   {
> -	int usec = UM_USEC_PER_SEC / UM_HZ;
> -	long long start_usecs = timespec_to_us(ts);
> -	struct timeval tv;
> -	struct itimerval interval;
> -
> -	/*
> -	 * It seems that rounding can increase the value returned from
> -	 * setitimer to larger than the one passed in.  Over time,
> -	 * this will cause the remaining time to be greater than the
> -	 * tick interval.  If this happens, then just reduce the first
> -	 * tick to the interval value.
> -	 */
> -	if (start_usecs > usec)
> -		start_usecs = usec;
> -
> -	start_usecs -= skew / UM_NSEC_PER_USEC;
> -	if (start_usecs < 0)
> -		start_usecs = 0;
> -
> -	tv = ((struct timeval) { .tv_sec  = start_usecs / UM_USEC_PER_SEC,
> -				 .tv_usec = start_usecs % UM_USEC_PER_SEC });
> -	interval = ((struct itimerval) { { 0, usec }, tv });
> -
> -	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
> -		return -errno;
> +	struct timespec ts;
>   
> -	return 0;
> +	clock_gettime(CLOCK_MONOTONIC,&ts);
> +	return timespec_to_ns(&ts);
>   }
> -#endif
>   
> -void idle_sleep(unsigned long long nsecs)
> +/**
> + * os_idle_sleep() - sleep for a given time of nsecs
> + * @nsecs: nanoseconds to sleep
> + */
> +void os_idle_sleep(unsigned long long nsecs)
>   {
>   	struct timespec ts;
>   
> -	/*
> -	 * nsecs can come in as zero, in which case, this starts a
> -	 * busy loop.  To prevent this, reset nsecs to the tick
> -	 * interval if it is zero.
> -	 */
> -	if (nsecs == 0)
> -		nsecs = UM_NSEC_PER_SEC / UM_HZ;
> -
> -	nsecs = sleep_time(nsecs);
> -	ts = ((struct timespec) { .tv_sec	= nsecs / UM_NSEC_PER_SEC,
> -				  .tv_nsec	= nsecs % UM_NSEC_PER_SEC });
> -
> -	if (nanosleep(&ts, &ts) == 0)
> -		deliver_alarm();
> -	after_sleep_interval(&ts);
> +	if (nsecs <= 0) {
> +		return;
> +	}
> +
> +	ts = ((struct timespec) {
> +			.tv_sec  = nsecs / UM_NSEC_PER_SEC,
> +			.tv_nsec = nsecs % UM_NSEC_PER_SEC
> +	});
> +
> +	clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, NULL);
>   }
>
>
>
>
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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Richard Weinberger]

On Tue, May 19, 2015 at 6:19 PM, Anton Ivanov
<anton.ivanov@kot-begemot.co.uk> wrote:
> Same story.
>
> Overall works quite well, the moment I give it the "dselect upgrade
> test" the userspace hangs.
>
> Kernel continues to work - forwarding, icmp, uml_mconsole are fine.

Do you know where it hangs?
Maybe the kernel does not get any scheduler tick and does not schedule a task..,

-- 
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//richard

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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Anton Ivanov]

On 19/05/15 17:39, Richard Weinberger wrote:
> On Tue, May 19, 2015 at 6:19 PM, Anton Ivanov
> <anton.ivanov@kot-begemot.co.uk> wrote:
>> Same story.
>>
>> Overall works quite well, the moment I give it the "dselect upgrade
>> test" the userspace hangs.
>>
>> Kernel continues to work - forwarding, icmp, uml_mconsole are fine.
> Do you know where it hangs?
> Maybe the kernel does not get any scheduler tick and does not schedule a task..,

Kernel continues to get ticks, timers increment, io also works.

If I strace the kernel I see a mix of SIGALRM (or in the oder version 
-USR2), SIGIO and SIGCHLD. Nothing out of the ordinary.

Uml mconsole works. I cannot get meaningful information because trying 
to invoke backtraces I get "SIGSEGV in SIGSEGV handler" for all 
processes. Memory looks OK too - 500MB+ free on a 1GB UML.

Syncronous vs asynchronous FS does not change it so it is not a variety 
of the writeout bug.

If I could get a bt for the userspace task and/or its stub we could have 
nailed it. I suspect it is spinning in skas/process.c for some reason. 
No idea why, but it takes 100% CPU.

A.

>


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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Richard Weinberger]

On Sun, May 17, 2015 at 11:25 AM, Thomas Meyer <thomas@m3y3r.de> wrote:
> Switch the UML clocksource from interval timers to posix interval timers
> and move to a monotonic timer.
>
> This fixes suspend&resume related timer issues and improves network
> performance as TCP state machines are now fed with the correct time;
> also correct QoS and traffic shaping.
>
> Signed-off-by: Thomas Meyer <thomas@m3y3r.de>

What tree is this patch against?
It does not clearly apply to Linus' tree.

-- 
Thanks,
//richard

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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Thomas Meyer]

Am 20.05.2015 12:12 vorm. schrieb Richard Weinberger <richard.weinberger@gmail.com>:
>
> On Sun, May 17, 2015 at 11:25 AM, Thomas Meyer <thomas@m3y3r.de> wrote: 
> > Switch the UML clocksource from interval timers to posix interval timers 
> > and move to a monotonic timer. 
> > 
> > This fixes suspend&resume related timer issues and improves network 
> > performance as TCP state machines are now fed with the correct time; 
> > also correct QoS and traffic shaping. 
> > 
> > Signed-off-by: Thomas Meyer <thomas@m3y3r.de> 
>
> What tree is this patch against? 
> It does not clearly apply to Linus' tree. 
>

Hi,

I did tested the patch against 4.1-rc3-something; will update the patch against the latest commit!


> -- 
> Thanks, 
> //richard 
>
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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Richard Weinberger]

Am 20.05.2015 um 07:26 schrieb Thomas Meyer:
> 
> Am 20.05.2015 12:12 vorm. schrieb Richard Weinberger <richard.weinberger@gmail.com>:
>>
>> On Sun, May 17, 2015 at 11:25 AM, Thomas Meyer <thomas@m3y3r.de> wrote: 
>>> Switch the UML clocksource from interval timers to posix interval timers 
>>> and move to a monotonic timer. 
>>>
>>> This fixes suspend&resume related timer issues and improves network 
>>> performance as TCP state machines are now fed with the correct time; 
>>> also correct QoS and traffic shaping. 
>>>
>>> Signed-off-by: Thomas Meyer <thomas@m3y3r.de> 
>>
>> What tree is this patch against? 
>> It does not clearly apply to Linus' tree. 
>>
> 
> Hi,
> 
> I did tested the patch against 4.1-rc3-something; will update the patch against the latest commit!

Ping.
Would be nice to have this patch for the 4.2 merge window.

Thanks,
//richard

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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Thomas Meyer]

Am Sonntag, den 31.05.2015, 13:15 +0200 schrieb Richard Weinberger:
> Am 20.05.2015 um 07:26 schrieb Thomas Meyer:
> > 
> > Am 20.05.2015 12:12 vorm. schrieb Richard Weinberger <
> > richard.weinberger@gmail.com>:
> > > 
> > > On Sun, May 17, 2015 at 11:25 AM, Thomas Meyer <thomas@m3y3r.de> 
> > > wrote: 
> > > > Switch the UML clocksource from interval timers to posix 
> > > > interval timers 
> > > > and move to a monotonic timer. 
> > > > 
> > > > This fixes suspend&resume related timer issues and improves 
> > > > network 
> > > > performance as TCP state machines are now fed with the correct 
> > > > time; 
> > > > also correct QoS and traffic shaping. 
> > > > 
> > > > Signed-off-by: Thomas Meyer <thomas@m3y3r.de> 
> > > 
> > > What tree is this patch against? 
> > > It does not clearly apply to Linus' tree. 
> > > 
> > 
> > Hi,
> > 
> > I did tested the patch against 4.1-rc3-something; will update the 
> > patch against the latest commit!
> 

Hi,

> Ping.
> Would be nice to have this patch for the 4.2 merge window.

I can provide you the current version of the patch, but I'm not sure if
it's ready for inclusion yet.
For example:
- With this patch I see new zombie processes of UML userspace
processes. I'm not sure what's going on here.
- Anton reported some hang he sees with this patch
- A person from cicso is worried about the potential idle CPU usage
after the patch, because of the many timers started, i.e. a host with
hundreds of UMLs.

Also meanwhile I think is not the correct thing to start a new timer
for each UML userspace process, because the timer will also trigger the
userspace process, even the corresponding process isn't scheduled by
the kernel currently. I think the previous behaviour with the itimer
was okay, because the virtual timer only did execute when the process
was executing which is the correct thing to do for the currently active
task in the UML kernel.
I see two solutions for above problem: cascade the kernel timer into
the current active task; there is actually no need to start a timer in
each userspace process.
Start/stop each timer when a userspace process becomes active resp.
becomes inactive again.
I hope above logic makes some sense at all! What do you think about
this?

with kind regards
thomas



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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Anton Ivanov]

On 31/05/15 20:00, Thomas Meyer wrote:
> Am Sonntag, den 31.05.2015, 13:15 +0200 schrieb Richard Weinberger:
>> Am 20.05.2015 um 07:26 schrieb Thomas Meyer:
>>> Am 20.05.2015 12:12 vorm. schrieb Richard Weinberger <
>>> richard.weinberger@gmail.com>:
>>>> On Sun, May 17, 2015 at 11:25 AM, Thomas Meyer <thomas@m3y3r.de> 
>>>> wrote: 
>>>>> Switch the UML clocksource from interval timers to posix 
>>>>> interval timers 
>>>>> and move to a monotonic timer. 
>>>>>
>>>>> This fixes suspend&resume related timer issues and improves 
>>>>> network 
>>>>> performance as TCP state machines are now fed with the correct 
>>>>> time; 
>>>>> also correct QoS and traffic shaping. 
>>>>>
>>>>> Signed-off-by: Thomas Meyer <thomas@m3y3r.de> 
>>>> What tree is this patch against? 
>>>> It does not clearly apply to Linus' tree. 
>>>>
>>> Hi,
>>>
>>> I did tested the patch against 4.1-rc3-something; will update the 
>>> patch against the latest commit!
> Hi,
>
>> Ping.
>> Would be nice to have this patch for the 4.2 merge window.
> I can provide you the current version of the patch, but I'm not sure if
> it's ready for inclusion yet.

Agree.

> For example:
> - With this patch I see new zombie processes of UML userspace
> processes. I'm not sure what's going on here.

+1

> - Anton reported some hang he sees with this patch

I did not have a chance to work on it last week, will try to find some
time this week. 

> - A person from cicso is worried about the potential idle CPU usage
> after the patch, because of the many timers started, i.e. a host with
> hundreds of UMLs.
This is less then the old CPU usage - checking time and rearming
nanosleeps and itimers is expensive.

>
> Also meanwhile I think is not the correct thing to start a new timer
> for each UML userspace process, because the timer will also trigger the
> userspace process, even the corresponding process isn't scheduled by
> the kernel currently. I think the previous behaviour with the itimer
> was okay, because the virtual timer only did execute when the process
> was executing which is the correct thing to do for the currently active
> task in the UML kernel.
> I see two solutions for above problem: cascade the kernel timer into
> the current active task; there is actually no need to start a timer in
> each userspace process.
> Start/stop each timer when a userspace process becomes active resp.
> becomes inactive again.
> I hope above logic makes some sense at all! What do you think about
> this?

Cascading the kernel timer looks like the correct solution.

A.

>
> with kind regards
> thomas
>
>
>
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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Richard Weinberger]

Am 31.05.2015 um 21:00 schrieb Thomas Meyer:
>> Ping.
>> Would be nice to have this patch for the 4.2 merge window.
> 
> I can provide you the current version of the patch, but I'm not sure if
> it's ready for inclusion yet.

That's fine. I'll look at it.
Just rebase it against Linus' tree or uml-next.
https://git.kernel.org/cgit/linux/kernel/git/rw/uml.git/log/?h=linux-next

> For example:
> - With this patch I see new zombie processes of UML userspace
> processes. I'm not sure what's going on here.
> - Anton reported some hang he sees with this patch
> - A person from cicso is worried about the potential idle CPU usage
> after the patch, because of the many timers started, i.e. a host with
> hundreds of UMLs.
> 
> Also meanwhile I think is not the correct thing to start a new timer
> for each UML userspace process, because the timer will also trigger the
> userspace process, even the corresponding process isn't scheduled by
> the kernel currently. I think the previous behaviour with the itimer
> was okay, because the virtual timer only did execute when the process
> was executing which is the correct thing to do for the currently active
> task in the UML kernel.
> I see two solutions for above problem: cascade the kernel timer into
> the current active task; there is actually no need to start a timer in
> each userspace process.
> Start/stop each timer when a userspace process becomes active resp.
> becomes inactive again.
> I hope above logic makes some sense at all! What do you think about
> this?

Hm, we definitely don't want a new timer for each userspace proc. The timer
has to work as a regular clock source.
But I'll have to read your/Anton's code in detail first.

Thanks,
//richard

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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Thomas Meyer]

Am Sonntag, den 31.05.2015, 23:49 +0200 schrieb Richard Weinberger:
> Am 31.05.2015 um 21:00 schrieb Thomas Meyer:
> > > Ping.
> > > Would be nice to have this patch for the 4.2 merge window.
> > 
> > I can provide you the current version of the patch, but I'm not 
> > sure if
> > it's ready for inclusion yet.
> 
> That's fine. I'll look at it.
> Just rebase it against Linus' tree or uml-next.
> https://git.kernel.org/cgit/linux/kernel/git/rw/uml.git/log/?h=linux
> -next
> > For example:
> > - With this patch I see new zombie processes of UML userspace
> > processes. I'm not sure what's going on here.
> > - Anton reported some hang he sees with this patch
> > - A person from cicso is worried about the potential idle CPU usage
> > after the patch, because of the many timers started, i.e. a host 
> > with
> > hundreds of UMLs.
> > 
> > Also meanwhile I think is not the correct thing to start a new 
> > timer
> > for each UML userspace process, because the timer will also trigger 
> > the
> > userspace process, even the corresponding process isn't scheduled 
> > by
> > the kernel currently. I think the previous behaviour with the 
> > itimer
> > was okay, because the virtual timer only did execute when the 
> > process
> > was executing which is the correct thing to do for the currently 
> > active
> > task in the UML kernel.
> > I see two solutions for above problem: cascade the kernel timer 
> > into
> > the current active task; there is actually no need to start a timer 
> > in
> > each userspace process.
> > Start/stop each timer when a userspace process becomes active resp.
> > becomes inactive again.
> > I hope above logic makes some sense at all! What do you think about
> > this?
> 
> Hm, we definitely don't want a new timer for each userspace proc. The 
> timer
> has to work as a regular clock source.
> But I'll have to read your/Anton's code in detail first.

Hi,

rebased against current Linus' tree:
- Currently I'm not sure at all why the individual itimers are created
for each usespace process and if we need to copy these mechanism for
posix interval timers.

Please have a look at the patch, this should apply cleanly against
linus tree:

commit c091d1f11649d39dbdd1653139954bf1feff0c80
Author: Thomas Meyer <thomas@m3y3r.de>
Date:   Sun May 31 19:40:22 2015 +0200

    um: Switch clocksource to hrtimers
    
    Switch the UML clocksource from interval timers to posix interval timers and
    move to a monotonic timer.
    
    This fixes suspend&resume related timer issues and improves network performance
    as TCP state machines are now fed with the correct time; also correct QoS and
    traffic shaping.
    
    Signed-off-by: Thomas Meyer <thomas@m3y3r.de>

diff --git a/arch/um/Makefile b/arch/um/Makefile
index 17d4460..a4a434f 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -130,7 +130,7 @@ export LDS_ELF_FORMAT := $(ELF_FORMAT)
 # The wrappers will select whether using "malloc" or the kernel allocator.
 LINK_WRAPS = -Wl,--wrap,malloc -Wl,--wrap,free -Wl,--wrap,calloc
 
-LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt))
+LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt)) -lrt
 
 # Used by link-vmlinux.sh which has special support for um link
 export CFLAGS_vmlinux := $(LINK-y) $(LINK_WRAPS) $(LD_FLAGS_CMDLINE)
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index d824528..2e738b0 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -217,7 +217,7 @@ extern int set_umid(char *name);
 extern char *get_umid(void);
 
 /* signal.c */
-extern void timer_init(void);
+extern void timer_set_signal_handler(void);
 extern void set_sigstack(void *sig_stack, int size);
 extern void remove_sigstack(void);
 extern void set_handler(int sig);
@@ -238,12 +238,16 @@ extern void um_early_printk(const char *s, unsigned int n);
 extern void os_fix_helper_signals(void);
 
 /* time.c */
-extern void idle_sleep(unsigned long long nsecs);
-extern int set_interval(void);
-extern int timer_one_shot(int ticks);
-extern long long disable_timer(void);
+extern void os_idle_sleep(unsigned long long nsecs);
+extern int os_timer_create(void* timer);
+extern int os_timer_set_interval(void* timer, void* its);
+extern int os_timer_one_shot(int ticks);
+extern long long os_timer_disable(void);
+extern long os_timer_remain(void* timer);
 extern void uml_idle_timer(void);
+extern long long os_persistent_clock_emulation(void);
 extern long long os_nsecs(void);
+extern long long os_vnsecs(void);
 
 /* skas/mem.c */
 extern long run_syscall_stub(struct mm_id * mm_idp,
diff --git a/arch/um/include/shared/skas/stub-data.h b/arch/um/include/shared/skas/stub-data.h
index f6ed92c..f98b9e2 100644
--- a/arch/um/include/shared/skas/stub-data.h
+++ b/arch/um/include/shared/skas/stub-data.h
@@ -6,12 +6,12 @@
 #ifndef __STUB_DATA_H
 #define __STUB_DATA_H
 
-#include <sys/time.h>
+#include <time.h>
 
 struct stub_data {
-       long offset;
+       unsigned long offset;
        int fd;
-       struct itimerval timer;
+       struct itimerspec timer;
        long err;
 };
 
diff --git a/arch/um/include/shared/timer-internal.h b/arch/um/include/shared/timer-internal.h
new file mode 100644
index 0000000..03e6f21
--- /dev/null
+++ b/arch/um/include/shared/timer-internal.h
@@ -0,0 +1,13 @@
+/*
+ * Copyright (C) 2012 - 2014 Cisco Systems
+ * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ */
+
+#ifndef __TIMER_INTERNAL_H__
+#define __TIMER_INTERNAL_H__
+
+#define TIMER_MULTIPLIER 256
+#define TIMER_MIN_DELTA  500
+
+#endif
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index 68b9119..3b936f8 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -27,6 +27,7 @@
 #include <kern_util.h>
 #include <os.h>
 #include <skas.h>
+#include <timer-internal.h>
 
 /*
  * This is a per-cpu array.  A processor only modifies its entry and it only
@@ -201,11 +202,8 @@ void initial_thread_cb(void (*proc)(void *), void *arg)
 
 void arch_cpu_idle(void)
 {
-       unsigned long long nsecs;
-
        cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
-       nsecs = disable_timer();
-       idle_sleep(nsecs);
+       os_idle_sleep(UM_NSEC_PER_SEC / UM_HZ);
        local_irq_enable();
 }
 
diff --git a/arch/um/kernel/skas/clone.c b/arch/um/kernel/skas/clone.c
index 289771d..814ec8b 100644
--- a/arch/um/kernel/skas/clone.c
+++ b/arch/um/kernel/skas/clone.c
@@ -24,6 +24,7 @@ void __attribute__ ((__section__ (".__syscall_stub")))
 stub_clone_handler(void)
 {
        struct stub_data *data = (struct stub_data *) STUB_DATA;
+       timer_t timerid;
        long err;
 
        err = stub_syscall2(__NR_clone, CLONE_PARENT | CLONE_FILES | SIGCHLD,
@@ -35,8 +36,14 @@ stub_clone_handler(void)
        if (err)
                goto out;
 
-       err = stub_syscall3(__NR_setitimer, ITIMER_VIRTUAL,
-                           (long) &data->timer, 0);
+       /* create posix interval timer */
+       err = stub_syscall3(__NR_timer_create, CLOCK_MONOTONIC, 0l, (long) &timerid);
+       if (err)
+               goto out;
+
+       /* set interval to the given value from copy_context_skas0() */
+       err = stub_syscall4(__NR_timer_settime, (long) timerid, 0l,
+                                               (long) &data->timer, 0l);
        if (err)
                goto out;
 
diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c
index 117568d..d15966c 100644
--- a/arch/um/kernel/time.c
+++ b/arch/um/kernel/time.c
@@ -1,4 +1,5 @@
 /*
+ * Copyright (C) 2012-2014 Cisco Systems
  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  * Licensed under the GPL
  */
@@ -8,10 +9,12 @@
 #include <linux/interrupt.h>
 #include <linux/jiffies.h>
 #include <linux/threads.h>
+#include <linux/spinlock.h>
 #include <asm/irq.h>
 #include <asm/param.h>
 #include <kern_util.h>
 #include <os.h>
+#include <timer-internal.h>
 
 void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
 {
@@ -22,18 +25,20 @@ void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
        local_irq_restore(flags);
 }
 
-static void itimer_set_mode(enum clock_event_mode mode,
+static void timer_set_mode(enum clock_event_mode mode,
                            struct clock_event_device *evt)
 {
        switch (mode) {
        case CLOCK_EVT_MODE_PERIODIC:
-               set_interval();
+               os_timer_set_interval(NULL, NULL);
                break;
 
+       case CLOCK_EVT_MODE_ONESHOT:
+               os_timer_one_shot(1);
+
        case CLOCK_EVT_MODE_SHUTDOWN:
        case CLOCK_EVT_MODE_UNUSED:
-       case CLOCK_EVT_MODE_ONESHOT:
-               disable_timer();
+               os_timer_disable();
                break;
 
        case CLOCK_EVT_MODE_RESUME:
@@ -41,68 +46,74 @@ static void itimer_set_mode(enum clock_event_mode mode,
        }
 }
 
-static int itimer_next_event(unsigned long delta,
+static int timer_next_event(unsigned long delta,
                             struct clock_event_device *evt)
 {
-       return timer_one_shot(delta + 1);
+       return os_timer_one_shot(delta);
 }
 
-static struct clock_event_device itimer_clockevent = {
-       .name           = "itimer",
+static struct clock_event_device timer_clockevent = {
+       .name           = "posix-timer",
        .rating         = 250,
        .cpumask        = cpu_all_mask,
        .features       = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
-       .set_mode       = itimer_set_mode,
-       .set_next_event = itimer_next_event,
-       .shift          = 32,
+       .set_mode       = timer_set_mode,
+       .set_next_event = timer_next_event,
+       .shift          = 0,
+       .max_delta_ns   = 0xffffffff,
+       .min_delta_ns   = TIMER_MIN_DELTA, //microsecond resolution should be enough for anyone, same as 640K RAM
        .irq            = 0,
+       .mult           = 1,
 };
 
-static irqreturn_t um_timer(int irq, void *dev)
+static irqreturn_t um_timer_irq(int irq, void *dev)
 {
-       (*itimer_clockevent.event_handler)(&itimer_clockevent);
+       (*timer_clockevent.event_handler)(&timer_clockevent);
 
        return IRQ_HANDLED;
 }
 
-static cycle_t itimer_read(struct clocksource *cs)
+static cycle_t timer_read(struct clocksource *cs)
 {
-       return os_nsecs() / 1000;
+       return os_nsecs() / TIMER_MULTIPLIER;
 }
 
-static struct clocksource itimer_clocksource = {
-       .name           = "itimer",
+static struct clocksource timer_clocksource = {
+       .name           = "timer",
        .rating         = 300,
-       .read           = itimer_read,
+       .read           = timer_read,
        .mask           = CLOCKSOURCE_MASK(64),
        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
-static void __init setup_itimer(void)
+static void __init timer_setup(void)
 {
        int err;
 
-       err = request_irq(TIMER_IRQ, um_timer, 0, "timer", NULL);
-       if (err != 0)
+       err = request_irq(TIMER_IRQ, um_timer_irq, IRQF_TIMER, "hr timer", NULL);
+       if (err != 0) {
                printk(KERN_ERR "register_timer : request_irq failed - "
                       "errno = %d\n", -err);
+               return;
+    }
+
+    err = os_timer_create(NULL);
+    if (err != 0) {
+        printk(KERN_ERR "creation of timer failed - errno = %d\n", -err);
+        return;
+    }
 
-       itimer_clockevent.mult = div_sc(HZ, NSEC_PER_SEC, 32);
-       itimer_clockevent.max_delta_ns =
-               clockevent_delta2ns(60 * HZ, &itimer_clockevent);
-       itimer_clockevent.min_delta_ns =
-               clockevent_delta2ns(1, &itimer_clockevent);
-       err = clocksource_register_hz(&itimer_clocksource, USEC_PER_SEC);
+       err = clocksource_register_hz(&timer_clocksource, NSEC_PER_SEC/TIMER_MULTIPLIER);
        if (err) {
                printk(KERN_ERR "clocksource_register_hz returned %d\n", err);
                return;
        }
-       clockevents_register_device(&itimer_clockevent);
+       clockevents_register_device(&timer_clockevent);
 }
 
 void read_persistent_clock(struct timespec *ts)
 {
-       long long nsecs = os_nsecs();
+       long long nsecs = os_persistent_clock_emulation();
 
        set_normalized_timespec(ts, nsecs / NSEC_PER_SEC,
                                nsecs % NSEC_PER_SEC);
@@ -110,6 +121,6 @@ void read_persistent_clock(struct timespec *ts)
 
 void __init time_init(void)
 {
-       timer_init();
-       late_time_init = setup_itimer;
+       timer_set_signal_handler();
+       late_time_init = timer_setup;
 }
diff --git a/arch/um/os-Linux/internal.h b/arch/um/os-Linux/internal.h
deleted file mode 100644
index 0dc2c9f..0000000
--- a/arch/um/os-Linux/internal.h
+++ /dev/null
@@ -1 +0,0 @@
-void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc);
diff --git a/arch/um/os-Linux/main.c b/arch/um/os-Linux/main.c
index df9191a..6e36f0f 100644
--- a/arch/um/os-Linux/main.c
+++ b/arch/um/os-Linux/main.c
@@ -163,13 +163,13 @@ int __init main(int argc, char **argv, char **envp)
 
        /*
         * This signal stuff used to be in the reboot case.  However,
-        * sometimes a SIGVTALRM can come in when we're halting (reproducably
+        * sometimes a timer signal can come in when we're halting (reproducably
         * when writing out gcov information, presumably because that takes
         * some time) and cause a segfault.
         */
 
-       /* stop timers and set SIGVTALRM to be ignored */
-       disable_timer();
+       /* stop timers and set timer signal to be ignored */
+       os_timer_disable();
 
        /* disable SIGIO for the fds and set SIGIO to be ignored */
        err = deactivate_all_fds();
diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
index 7b605e4..4a9be55 100644
--- a/arch/um/os-Linux/signal.c
+++ b/arch/um/os-Linux/signal.c
@@ -13,7 +13,6 @@
 #include <kern_util.h>
 #include <os.h>
 #include <sysdep/mcontext.h>
-#include "internal.h"
 
 void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
        [SIGTRAP]       = relay_signal,
@@ -23,7 +22,8 @@ void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
        [SIGBUS]        = bus_handler,
        [SIGSEGV]       = segv_handler,
        [SIGIO]         = sigio_handler,
-       [SIGVTALRM]     = timer_handler };
+       [SIGALRM]       = timer_handler
+};
 
 static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
 {
@@ -38,7 +38,7 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
        }
 
        /* enable signals if sig isn't IRQ signal */
-       if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGVTALRM))
+       if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGALRM))
                unblock_signals();
 
        (*sig_info[sig])(sig, si, &r);
@@ -55,8 +55,8 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
 #define SIGIO_BIT 0
 #define SIGIO_MASK (1 << SIGIO_BIT)
 
-#define SIGVTALRM_BIT 1
-#define SIGVTALRM_MASK (1 << SIGVTALRM_BIT)
+#define SIGALRM_BIT 1
+#define SIGALRM_MASK (1 << SIGALRM_BIT)
 
 static int signals_enabled;
 static unsigned int signals_pending;
@@ -78,46 +78,47 @@ void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
        set_signals(enabled);
 }
 
-static void real_alarm_handler(mcontext_t *mc)
+static void timer_real_alarm_handler(mcontext_t *mc)
 {
        struct uml_pt_regs regs;
 
        if (mc != NULL)
                get_regs_from_mc(&regs, mc);
        regs.is_user = 0;
-       unblock_signals();
-       timer_handler(SIGVTALRM, NULL, &regs);
+       timer_handler(SIGALRM, NULL, &regs);
 }
 
-void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
+void timer_alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
 {
        int enabled;
 
        enabled = signals_enabled;
        if (!signals_enabled) {
-               signals_pending |= SIGVTALRM_MASK;
+               signals_pending |= SIGALRM_MASK;
                return;
        }
 
        block_signals();
-
-       real_alarm_handler(mc);
+       timer_real_alarm_handler(mc);
        set_signals(enabled);
 }
 
-void timer_init(void)
+void timer_set_signal_handler(void)
 {
-       set_handler(SIGVTALRM);
+       set_handler(SIGALRM);
 }
 
 void set_sigstack(void *sig_stack, int size)
 {
-       stack_t stack = ((stack_t) { .ss_flags  = 0,
-                                    .ss_sp     = (__ptr_t) sig_stack,
-                                    .ss_size   = size - sizeof(void *) });
+       stack_t stack = ((stack_t) {
+                   .ss_flags = 0,
+                               .ss_sp    = (__ptr_t) sig_stack,
+                               .ss_size  = size - sizeof(void *)
+       });
 
-       if (sigaltstack(&stack, NULL) != 0)
+       if (sigaltstack(&stack, NULL) != 0) {
                panic("enabling signal stack failed, errno = %d\n", errno);
+       }
 }
 
 static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
@@ -129,10 +130,9 @@ static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
 
        [SIGIO] = sig_handler,
        [SIGWINCH] = sig_handler,
-       [SIGVTALRM] = alarm_handler
+       [SIGALRM] = timer_alarm_handler
 };
 
-
 static void hard_handler(int sig, siginfo_t *si, void *p)
 {
        struct ucontext *uc = p;
@@ -186,9 +186,9 @@ void set_handler(int sig)
 
        /* block irq ones */
        sigemptyset(&action.sa_mask);
-       sigaddset(&action.sa_mask, SIGVTALRM);
        sigaddset(&action.sa_mask, SIGIO);
        sigaddset(&action.sa_mask, SIGWINCH);
+       sigaddset(&action.sa_mask, SIGALRM);
 
        if (sig == SIGSEGV)
                flags |= SA_NODEFER;
@@ -281,8 +281,8 @@ void unblock_signals(void)
                if (save_pending & SIGIO_MASK)
                        sig_handler_common(SIGIO, NULL, NULL);
 
-               if (save_pending & SIGVTALRM_MASK)
-                       real_alarm_handler(NULL);
+               if (save_pending & SIGALRM_MASK)
+                       timer_real_alarm_handler(NULL);
        }
 }
 
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index 7a97775..4761f8b 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -45,7 +45,7 @@ static int ptrace_dump_regs(int pid)
  * Signals that are OK to receive in the stub - we'll just continue it.
  * SIGWINCH will happen when UML is inside a detached screen.
  */
-#define STUB_SIG_MASK ((1 << SIGVTALRM) | (1 << SIGWINCH))
+#define STUB_SIG_MASK ((1 << SIGALRM) | (1 << SIGWINCH))
 
 /* Signals that the stub will finish with - anything else is an error */
 #define STUB_DONE_MASK (1 << SIGTRAP)
@@ -181,12 +181,23 @@ static int userspace_tramp(void *stack)
        void *addr;
        int err, fd;
        unsigned long long offset;
+       timer_t timer;
+
+       struct stub_data *data = (struct stub_data *) stack;
 
        ptrace(PTRACE_TRACEME, 0, 0, 0);
 
        signal(SIGTERM, SIG_DFL);
        signal(SIGWINCH, SIG_IGN);
-       err = set_interval();
+
+       err = os_timer_create(&timer);
+       if (err) {
+               printk(UM_KERN_ERR "userspace_tramp - creation of timer failed, "
+                      "errno = %d\n", err);
+               exit(1);
+       }
+
+       err = os_timer_set_interval(&timer, &data->timer);
        if (err) {
                printk(UM_KERN_ERR "userspace_tramp - setting timer failed, "
                       "errno = %d\n", err);
@@ -249,8 +260,9 @@ int userspace_pid[NR_CPUS];
 int start_userspace(unsigned long stub_stack)
 {
        void *stack;
-       unsigned long sp;
+       unsigned long sp, remain;
        int pid, status, n, flags, err;
+       struct stub_data *data = (struct stub_data *) stub_stack;
 
        stack = mmap(NULL, UM_KERN_PAGE_SIZE,
                     PROT_READ | PROT_WRITE | PROT_EXEC,
@@ -266,6 +278,18 @@ int start_userspace(unsigned long stub_stack)
 
        flags = CLONE_FILES | SIGCHLD;
 
+       remain = os_timer_remain(NULL);
+       if (remain == 0)
+               remain = UM_NSEC_PER_SEC / UM_HZ;
+
+       *data = ((struct stub_data) { 
+                       .timer  = ((struct itimerspec)
+                               { .it_value.tv_sec  = 0,
+                                 .it_value.tv_nsec = remain,
+                                 .it_interval.tv_sec  = 0,
+                                 .it_interval.tv_nsec = UM_NSEC_PER_SEC / UM_HZ })
+       });
+
        pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
        if (pid < 0) {
                err = -errno;
@@ -282,7 +306,7 @@ int start_userspace(unsigned long stub_stack)
                               "errno = %d\n", errno);
                        goto out_kill;
                }
-       } while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGVTALRM));
+       } while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGALRM));
 
        if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
                err = -EINVAL;
@@ -315,8 +339,6 @@ int start_userspace(unsigned long stub_stack)
 
 void userspace(struct uml_pt_regs *regs)
 {
-       struct itimerval timer;
-       unsigned long long nsecs, now;
        int err, status, op, pid = userspace_pid[0];
        /* To prevent races if using_sysemu changes under us.*/
        int local_using_sysemu;
@@ -325,13 +347,8 @@ void userspace(struct uml_pt_regs *regs)
        /* Handle any immediate reschedules or signals */
        interrupt_end();
 
-       if (getitimer(ITIMER_VIRTUAL, &timer))
-               printk(UM_KERN_ERR "Failed to get itimer, errno = %d\n", errno);
-       nsecs = timer.it_value.tv_sec * UM_NSEC_PER_SEC +
-               timer.it_value.tv_usec * UM_NSEC_PER_USEC;
-       nsecs += os_nsecs();
-
        while (1) {
+
                /*
                 * This can legitimately fail if the process loads a
                 * bogus value into a segment register.  It will
@@ -401,19 +418,7 @@ void userspace(struct uml_pt_regs *regs)
                        case SIGTRAP:
                                relay_signal(SIGTRAP, (struct siginfo *)&si, regs);
                                break;
-                       case SIGVTALRM:
-                               now = os_nsecs();
-                               if (now < nsecs)
-                                       break;
-                               block_signals();
-                               (*sig_info[sig])(sig, (struct siginfo *)&si, regs);
-                               unblock_signals();
-                               nsecs = timer.it_value.tv_sec *
-                                       UM_NSEC_PER_SEC +
-                                       timer.it_value.tv_usec *
-                                       UM_NSEC_PER_USEC;
-                               nsecs += os_nsecs();
-                               break;
+                       case SIGALRM:
                        case SIGIO:
                        case SIGILL:
                        case SIGBUS:
@@ -460,8 +465,8 @@ __initcall(init_thread_regs);
 
 int copy_context_skas0(unsigned long new_stack, int pid)
 {
-       struct timeval tv = { .tv_sec = 0, .tv_usec = UM_USEC_PER_SEC / UM_HZ };
        int err;
+       unsigned long remain;
        unsigned long current_stack = current_stub_stack();
        struct stub_data *data = (struct stub_data *) current_stack;
        struct stub_data *child_data = (struct stub_data *) new_stack;
@@ -472,11 +477,19 @@ int copy_context_skas0(unsigned long new_stack, int pid)
         * prepare offset and fd of child's stack as argument for parent's
         * and child's mmap2 calls
         */
-       *data = ((struct stub_data) { .offset   = MMAP_OFFSET(new_offset),
-                                     .fd       = new_fd,
-                                     .timer    = ((struct itimerval)
-                                                  { .it_value = tv,
-                                                    .it_interval = tv }) });
+       remain = os_timer_remain(NULL);
+       if (remain == 0)
+               remain = UM_NSEC_PER_SEC / UM_HZ;
+
+       *data = ((struct stub_data) { 
+                       .offset = MMAP_OFFSET(new_offset),
+                       .fd     = new_fd,
+                       .timer  = ((struct itimerspec)
+                                            { .it_value.tv_sec  = 0,
+                                              .it_value.tv_nsec = remain,
+                                              .it_interval.tv_sec  = 0,
+                                              .it_interval.tv_nsec = UM_NSEC_PER_SEC / UM_HZ })
+       });
 
        err = ptrace_setregs(pid, thread_regs);
        if (err < 0) {
diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c
index e9824d5..0e2bb7d 100644
--- a/arch/um/os-Linux/time.c
+++ b/arch/um/os-Linux/time.c
@@ -1,4 +1,5 @@
 /*
+ * Copyright (C) 2012-2014 Cisco Systems
  * Copyright (C) 2000 - 2007 Jeff Dike (jdike{addtoit,linux.intel}.com)
  * Licensed under the GPL
  */
@@ -10,177 +11,172 @@
 #include <sys/time.h>
 #include <kern_util.h>
 #include <os.h>
-#include "internal.h"
+#include <string.h>
+#include <timer-internal.h>
 
-int set_interval(void)
-{
-       int usec = UM_USEC_PER_SEC / UM_HZ;
-       struct itimerval interval = ((struct itimerval) { { 0, usec },
-                                                         { 0, usec } });
-
-       if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
-               return -errno;
+static timer_t event_high_res_timer = 0;
 
-       return 0;
+static inline long long timeval_to_ns(const struct timeval *tv)
+{
+       return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
+               tv->tv_usec * UM_NSEC_PER_USEC;
 }
 
-int timer_one_shot(int ticks)
+static inline long long timespec_to_ns(const struct timespec *ts)
 {
-       unsigned long usec = ticks * UM_USEC_PER_SEC / UM_HZ;
-       unsigned long sec = usec / UM_USEC_PER_SEC;
-       struct itimerval interval;
-
-       usec %= UM_USEC_PER_SEC;
-       interval = ((struct itimerval) { { 0, 0 }, { sec, usec } });
+       return ((long long) ts->tv_sec * UM_NSEC_PER_SEC) +
+               ts->tv_nsec;
+}
 
-       if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
-               return -errno;
+long long os_persistent_clock_emulation (void) {
+       struct timespec realtime_tp;
 
-       return 0;
+       clock_gettime(CLOCK_REALTIME, &realtime_tp);
+       return timespec_to_ns(&realtime_tp);
 }
 
 /**
- * timeval_to_ns - Convert timeval to nanoseconds
- * @ts:                pointer to the timeval variable to be converted
- *
- * Returns the scalar nanosecond representation of the timeval
- * parameter.
- *
- * Ripped from linux/time.h because it's a kernel header, and thus
- * unusable from here.
+ * os_timer_create() - create an new posix (interval) timer
  */
-static inline long long timeval_to_ns(const struct timeval *tv)
-{
-       return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
-               tv->tv_usec * UM_NSEC_PER_USEC;
+int os_timer_create(void* timer) {
+
+       timer_t* t = timer;
+
+       if(t == NULL) {
+               t = &event_high_res_timer;
+       }
+
+       if (timer_create(
+               CLOCK_MONOTONIC,
+               NULL,
+               t) == -1) {
+               return -1;
+       }
+       return 0;
 }
 
-long long disable_timer(void)
+int os_timer_set_interval(void* timer, void* i)
 {
-       struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } });
-       long long remain, max = UM_NSEC_PER_SEC / UM_HZ;
+       struct itimerspec its;
+       unsigned long long nsec;
+       timer_t* t = timer;
+       struct itimerspec* its_in = i;
 
-       if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0)
-               printk(UM_KERN_ERR "disable_timer - setitimer failed, "
-                      "errno = %d\n", errno);
+       if(t == NULL) {
+               t = &event_high_res_timer;
+       }
 
-       remain = timeval_to_ns(&time.it_value);
-       if (remain > max)
-               remain = max;
+       nsec = UM_NSEC_PER_SEC / UM_HZ;
 
-       return remain;
-}
+       if(its_in != NULL) {
+               its.it_value.tv_sec = its_in->it_value.tv_sec;
+               its.it_value.tv_nsec = its_in->it_value.tv_nsec;
+       } else {
+               its.it_value.tv_sec = 0;
+               its.it_value.tv_nsec = nsec;
+       }
 
-long long os_nsecs(void)
-{
-       struct timeval tv;
+       its.it_interval.tv_sec = 0;
+       its.it_interval.tv_nsec = nsec;
 
-       gettimeofday(&tv, NULL);
-       return timeval_to_ns(&tv);
-}
+       if(timer_settime(*t, 0, &its, NULL) == -1) {
+               return -errno;
+       }
 
-#ifdef UML_CONFIG_NO_HZ_COMMON
-static int after_sleep_interval(struct timespec *ts)
-{
        return 0;
 }
 
-static void deliver_alarm(void)
+/**
+ * os_timer_remain() - returns the remaining nano seconds of the given interval
+ *                     timer
+ * Because this is the remaining time of an interval timer, which correspondends
+ * to HZ, this value can never be bigger than one second. Just
+ * the nanosecond part of the timer is returned.
+ * The returned time is relative to the start time of the interval timer.
+ * Return an negative value in an error case.
+ */
+long os_timer_remain(void* timer)
 {
-       alarm_handler(SIGVTALRM, NULL, NULL);
-}
+       struct itimerspec its;
+       timer_t* t = timer;
 
-static unsigned long long sleep_time(unsigned long long nsecs)
-{
-       return nsecs;
-}
+       if(t == NULL) {
+               t = &event_high_res_timer;
+       }
 
-#else
-unsigned long long last_tick;
-unsigned long long skew;
+       if(timer_gettime(t, &its) == -1) {
+               return -errno;
+       }
+
+       return its.it_value.tv_nsec;
+}
 
-static void deliver_alarm(void)
+int os_timer_one_shot(int ticks)
 {
-       unsigned long long this_tick = os_nsecs();
-       int one_tick = UM_NSEC_PER_SEC / UM_HZ;
+       struct itimerspec its;
+       unsigned long long nsec;
+       unsigned long sec;
 
-       /* Protection against the host's time going backwards */
-       if ((last_tick != 0) && (this_tick < last_tick))
-               this_tick = last_tick;
+    nsec = (ticks + 1);
+    sec = nsec / UM_NSEC_PER_SEC;
+       nsec = nsec % UM_NSEC_PER_SEC;
 
-       if (last_tick == 0)
-               last_tick = this_tick - one_tick;
+       its.it_value.tv_sec = nsec / UM_NSEC_PER_SEC;
+       its.it_value.tv_nsec = nsec;
 
-       skew += this_tick - last_tick;
+       its.it_interval.tv_sec = 0;
+       its.it_interval.tv_nsec = 0; // we cheat here
 
-       while (skew >= one_tick) {
-               alarm_handler(SIGVTALRM, NULL, NULL);
-               skew -= one_tick;
-       }
-
-       last_tick = this_tick;
+       timer_settime(event_high_res_timer, 0, &its, NULL);
+       return 0;
 }
 
-static unsigned long long sleep_time(unsigned long long nsecs)
+/**
+ * os_timer_disable() - disable the posix (interval) timer
+ * Returns the remaining interval timer time in nanoseconds
+ */
+long long os_timer_disable(void)
 {
-       return nsecs > skew ? nsecs - skew : 0;
+       struct itimerspec its;
+
+       memset(&its, 0, sizeof(struct itimerspec));
+       timer_settime(event_high_res_timer, 0, &its, &its);
+
+       return its.it_value.tv_sec * UM_NSEC_PER_SEC + its.it_value.tv_nsec;
 }
 
-static inline long long timespec_to_us(const struct timespec *ts)
+long long os_vnsecs(void)
 {
-       return ((long long) ts->tv_sec * UM_USEC_PER_SEC) +
-               ts->tv_nsec / UM_NSEC_PER_USEC;
+       struct timespec ts;
+
+       clock_gettime(CLOCK_PROCESS_CPUTIME_ID,&ts);
+       return timespec_to_ns(&ts);
 }
 
-static int after_sleep_interval(struct timespec *ts)
+long long os_nsecs(void)
 {
-       int usec = UM_USEC_PER_SEC / UM_HZ;
-       long long start_usecs = timespec_to_us(ts);
-       struct timeval tv;
-       struct itimerval interval;
-
-       /*
-        * It seems that rounding can increase the value returned from
-        * setitimer to larger than the one passed in.  Over time,
-        * this will cause the remaining time to be greater than the
-        * tick interval.  If this happens, then just reduce the first
-        * tick to the interval value.
-        */
-       if (start_usecs > usec)
-               start_usecs = usec;
-
-       start_usecs -= skew / UM_NSEC_PER_USEC;
-       if (start_usecs < 0)
-               start_usecs = 0;
-
-       tv = ((struct timeval) { .tv_sec  = start_usecs / UM_USEC_PER_SEC,
-                                .tv_usec = start_usecs % UM_USEC_PER_SEC });
-       interval = ((struct itimerval) { { 0, usec }, tv });
-
-       if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
-               return -errno;
+       struct timespec ts;
 
-       return 0;
+       clock_gettime(CLOCK_MONOTONIC,&ts);
+       return timespec_to_ns(&ts);
 }
-#endif
 
-void idle_sleep(unsigned long long nsecs)
+/**
+ * os_idle_sleep() - sleep for a given time of nsecs
+ * @nsecs: nanoseconds to sleep
+ */
+void os_idle_sleep(unsigned long long nsecs)
 {
        struct timespec ts;
 
-       /*
-        * nsecs can come in as zero, in which case, this starts a
-        * busy loop.  To prevent this, reset nsecs to the tick
-        * interval if it is zero.
-        */
-       if (nsecs == 0)
-               nsecs = UM_NSEC_PER_SEC / UM_HZ;
-
-       nsecs = sleep_time(nsecs);
-       ts = ((struct timespec) { .tv_sec       = nsecs / UM_NSEC_PER_SEC,
-                                 .tv_nsec      = nsecs % UM_NSEC_PER_SEC });
-
-       if (nanosleep(&ts, &ts) == 0)
-               deliver_alarm();
-       after_sleep_interval(&ts);
+       if (nsecs <= 0) {
+               return;
+       }
+
+       ts = ((struct timespec) {
+                       .tv_sec  = nsecs / UM_NSEC_PER_SEC,
+                       .tv_nsec = nsecs % UM_NSEC_PER_SEC
+       });
+
+       clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, NULL);
 }



------------------------------------------------------------------------------
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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Thomas Meyer]

Am Sonntag, den 31.05.2015, 20:10 +0100 schrieb Anton Ivanov:
> On 31/05/15 20:00, Thomas Meyer wrote:
> > Am Sonntag, den 31.05.2015, 13:15 +0200 schrieb Richard Weinberger:
> > > Am 20.05.2015 um 07:26 schrieb Thomas Meyer:
> > > > Am 20.05.2015 12:12 vorm. schrieb Richard Weinberger <
> > > > richard.weinberger@gmail.com>:
> > > > > On Sun, May 17, 2015 at 11:25 AM, Thomas Meyer <
> > > > > thomas@m3y3r.de> 
> > > > > wrote: 
> > > > > > Switch the UML clocksource from interval timers to posix 
> > > > > > interval timers 
> > > > > > and move to a monotonic timer. 
> > > > > > 
> > > > > > This fixes suspend&resume related timer issues and improves 
> > > > > > 
> > > > > > network 
> > > > > > performance as TCP state machines are now fed with the 
> > > > > > correct 
> > > > > > time; 
> > > > > > also correct QoS and traffic shaping. 
> > > > > > 
> > > > > > Signed-off-by: Thomas Meyer <thomas@m3y3r.de> 
> > > > > What tree is this patch against? 
> > > > > It does not clearly apply to Linus' tree. 
> > > > > 
> > > > Hi,
> > > > 
> > > > I did tested the patch against 4.1-rc3-something; will update 
> > > > the 
> > > > patch against the latest commit!
> > Hi,
> > 
> > > Ping.
> > > Would be nice to have this patch for the 4.2 merge window.
> > I can provide you the current version of the patch, but I'm not 
> > sure if
> > it's ready for inclusion yet.
> 
> Agree.
> 
> > For example:
> > - With this patch I see new zombie processes of UML userspace
> > processes. I'm not sure what's going on here.
> 
> +1
> 
> > - Anton reported some hang he sees with this patch
> 
> I did not have a chance to work on it last week, will try to find 
> some
> time this week. 
> 
> > - A person from cicso is worried about the potential idle CPU usage
> > after the patch, because of the many timers started, i.e. a host 
> > with
> > hundreds of UMLs.
> This is less then the old CPU usage - checking time and rearming
> nanosleeps and itimers is expensive.
> 
> > 
> > Also meanwhile I think is not the correct thing to start a new 
> > timer
> > for each UML userspace process, because the timer will also trigger 
> > the
> > userspace process, even the corresponding process isn't scheduled 
> > by
> > the kernel currently. I think the previous behaviour with the 
> > itimer
> > was okay, because the virtual timer only did execute when the 
> > process
> > was executing which is the correct thing to do for the currently 
> > active
> > task in the UML kernel.
> > I see two solutions for above problem: cascade the kernel timer 
> > into
> > the current active task; there is actually no need to start a timer 
> > in
> > each userspace process.
> > Start/stop each timer when a userspace process becomes active resp.
> > becomes inactive again.
> > I hope above logic makes some sense at all! What do you think about
> > this?
> 
> Cascading the kernel timer looks like the correct solution.

Hi,

below patch get's rid of all userspace timers.
When a kernel timer interrupt is received the userspace process of the
corresponding task is signaled via SIGALRM.
The SIGALRM signal forces the userspace process to go back into
userspace() function. There the SIGALRM signal is ignored as the
interrupt was already processed anyway by the uml kernel.

what do you think about this approach?

Can you give this patch a try

with kind regards
thomas

diff --git a/arch/um/Makefile b/arch/um/Makefile
index 17d4460..a4a434f 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -130,7 +130,7 @@ export LDS_ELF_FORMAT := $(ELF_FORMAT)
 # The wrappers will select whether using "malloc" or the kernel allocator.
 LINK_WRAPS = -Wl,--wrap,malloc -Wl,--wrap,free -Wl,--wrap,calloc
 
-LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt))
+LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt)) -lrt
 
 # Used by link-vmlinux.sh which has special support for um link
 export CFLAGS_vmlinux := $(LINK-y) $(LINK_WRAPS) $(LD_FLAGS_CMDLINE)
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index d824528..8f8f5d7 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -183,6 +183,7 @@ extern int create_mem_file(unsigned long long len);
 /* process.c */
 extern unsigned long os_process_pc(int pid);
 extern int os_process_parent(int pid);
+extern void os_alarm_process(int pid);
 extern void os_stop_process(int pid);
 extern void os_kill_process(int pid, int reap_child);
 extern void os_kill_ptraced_process(int pid, int reap_child);
@@ -217,7 +218,7 @@ extern int set_umid(char *name);
 extern char *get_umid(void);
 
 /* signal.c */
-extern void timer_init(void);
+extern void timer_set_signal_handler(void);
 extern void set_sigstack(void *sig_stack, int size);
 extern void remove_sigstack(void);
 extern void set_handler(int sig);
@@ -238,12 +239,16 @@ extern void um_early_printk(const char *s, unsigned int n);
 extern void os_fix_helper_signals(void);
 
 /* time.c */
-extern void idle_sleep(unsigned long long nsecs);
-extern int set_interval(void);
-extern int timer_one_shot(int ticks);
-extern long long disable_timer(void);
+extern void os_idle_sleep(unsigned long long nsecs);
+extern int os_timer_create(void* timer);
+extern int os_timer_set_interval(void* timer, void* its);
+extern int os_timer_one_shot(int ticks);
+extern long long os_timer_disable(void);
+extern long os_timer_remain(void* timer);
 extern void uml_idle_timer(void);
+extern long long os_persistent_clock_emulation(void);
 extern long long os_nsecs(void);
+extern long long os_vnsecs(void);
 
 /* skas/mem.c */
 extern long run_syscall_stub(struct mm_id * mm_idp,
diff --git a/arch/um/include/shared/skas/stub-data.h b/arch/um/include/shared/skas/stub-data.h
index f6ed92c..e09d8fd 100644
--- a/arch/um/include/shared/skas/stub-data.h
+++ b/arch/um/include/shared/skas/stub-data.h
@@ -6,12 +6,11 @@
 #ifndef __STUB_DATA_H
 #define __STUB_DATA_H
 
-#include <sys/time.h>
+#include <time.h>
 
 struct stub_data {
-       long offset;
+       unsigned long offset;
        int fd;
-       struct itimerval timer;
        long err;
 };
 
diff --git a/arch/um/include/shared/timer-internal.h b/arch/um/include/shared/timer-internal.h
new file mode 100644
index 0000000..03e6f21
--- /dev/null
+++ b/arch/um/include/shared/timer-internal.h
@@ -0,0 +1,13 @@
+/*
+ * Copyright (C) 2012 - 2014 Cisco Systems
+ * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ */
+
+#ifndef __TIMER_INTERNAL_H__
+#define __TIMER_INTERNAL_H__
+
+#define TIMER_MULTIPLIER 256
+#define TIMER_MIN_DELTA  500
+
+#endif
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index 68b9119..2ce38c1 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -27,6 +27,7 @@
 #include <kern_util.h>
 #include <os.h>
 #include <skas.h>
+#include <timer-internal.h>
 
 /*
  * This is a per-cpu array.  A processor only modifies its entry and it only
@@ -201,11 +202,8 @@ void initial_thread_cb(void (*proc)(void *), void *arg)
 
 void arch_cpu_idle(void)
 {
-       unsigned long long nsecs;
-
        cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
-       nsecs = disable_timer();
-       idle_sleep(nsecs);
+       os_idle_sleep(UM_NSEC_PER_SEC);
        local_irq_enable();
 }
 
diff --git a/arch/um/kernel/skas/clone.c b/arch/um/kernel/skas/clone.c
index 289771d..498148b 100644
--- a/arch/um/kernel/skas/clone.c
+++ b/arch/um/kernel/skas/clone.c
@@ -35,11 +35,6 @@ stub_clone_handler(void)
        if (err)
                goto out;
 
-       err = stub_syscall3(__NR_setitimer, ITIMER_VIRTUAL,
-                           (long) &data->timer, 0);
-       if (err)
-               goto out;
-
        remap_stack(data->fd, data->offset);
        goto done;
 
diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c
index 117568d..29f1125 100644
--- a/arch/um/kernel/time.c
+++ b/arch/um/kernel/time.c
@@ -1,4 +1,5 @@
 /*
+ * Copyright (C) 2012-2014 Cisco Systems
  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  * Licensed under the GPL
  */
@@ -7,11 +8,15 @@
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/jiffies.h>
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
 #include <linux/threads.h>
 #include <asm/irq.h>
 #include <asm/param.h>
 #include <kern_util.h>
 #include <os.h>
+#include <timer-internal.h>
 
 void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
 {
@@ -22,18 +27,20 @@ void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
        local_irq_restore(flags);
 }
 
-static void itimer_set_mode(enum clock_event_mode mode,
+static void timer_set_mode(enum clock_event_mode mode,
                            struct clock_event_device *evt)
 {
        switch (mode) {
        case CLOCK_EVT_MODE_PERIODIC:
-               set_interval();
+               os_timer_set_interval(NULL, NULL);
                break;
 
+       case CLOCK_EVT_MODE_ONESHOT:
+               os_timer_one_shot(1);
+
        case CLOCK_EVT_MODE_SHUTDOWN:
        case CLOCK_EVT_MODE_UNUSED:
-       case CLOCK_EVT_MODE_ONESHOT:
-               disable_timer();
+               os_timer_disable();
                break;
 
        case CLOCK_EVT_MODE_RESUME:
@@ -41,68 +48,79 @@ static void itimer_set_mode(enum clock_event_mode mode,
        }
 }
 
-static int itimer_next_event(unsigned long delta,
+static int timer_next_event(unsigned long delta,
                             struct clock_event_device *evt)
 {
-       return timer_one_shot(delta + 1);
+       return os_timer_one_shot(delta);
 }
 
-static struct clock_event_device itimer_clockevent = {
-       .name           = "itimer",
+static struct clock_event_device timer_clockevent = {
+       .name           = "posix-timer",
        .rating         = 250,
        .cpumask        = cpu_all_mask,
        .features       = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
-       .set_mode       = itimer_set_mode,
-       .set_next_event = itimer_next_event,
-       .shift          = 32,
+       .set_mode       = timer_set_mode,
+       .set_next_event = timer_next_event,
+       .shift          = 0,
+       .max_delta_ns   = 0xffffffff,
+       .min_delta_ns   = TIMER_MIN_DELTA, //microsecond resolution should be enough for anyone, same as 640K RAM
        .irq            = 0,
+       .mult           = 1,
 };
 
-static irqreturn_t um_timer(int irq, void *dev)
+static irqreturn_t um_timer_irq(int irq, void *dev)
 {
-       (*itimer_clockevent.event_handler)(&itimer_clockevent);
+       if (get_current()->mm != NULL)
+       {
+               os_alarm_process(get_current()->mm->context.id.u.pid);
+       }
+
+       (*timer_clockevent.event_handler)(&timer_clockevent);
 
        return IRQ_HANDLED;
 }
 
-static cycle_t itimer_read(struct clocksource *cs)
+static cycle_t timer_read(struct clocksource *cs)
 {
-       return os_nsecs() / 1000;
+       return os_nsecs() / TIMER_MULTIPLIER;
 }
 
-static struct clocksource itimer_clocksource = {
-       .name           = "itimer",
+static struct clocksource timer_clocksource = {
+       .name           = "timer",
        .rating         = 300,
-       .read           = itimer_read,
+       .read           = timer_read,
        .mask           = CLOCKSOURCE_MASK(64),
        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
-static void __init setup_itimer(void)
+static void __init timer_setup(void)
 {
        int err;
 
-       err = request_irq(TIMER_IRQ, um_timer, 0, "timer", NULL);
-       if (err != 0)
+       err = request_irq(TIMER_IRQ, um_timer_irq, IRQF_TIMER, "hr timer", NULL);
+       if (err != 0) {
                printk(KERN_ERR "register_timer : request_irq failed - "
                       "errno = %d\n", -err);
+               return;
+    }
+
+    err = os_timer_create(NULL);
+    if (err != 0) {
+        printk(KERN_ERR "creation of timer failed - errno = %d\n", -err);
+        return;
+    }
 
-       itimer_clockevent.mult = div_sc(HZ, NSEC_PER_SEC, 32);
-       itimer_clockevent.max_delta_ns =
-               clockevent_delta2ns(60 * HZ, &itimer_clockevent);
-       itimer_clockevent.min_delta_ns =
-               clockevent_delta2ns(1, &itimer_clockevent);
-       err = clocksource_register_hz(&itimer_clocksource, USEC_PER_SEC);
+       err = clocksource_register_hz(&timer_clocksource, NSEC_PER_SEC/TIMER_MULTIPLIER);
        if (err) {
                printk(KERN_ERR "clocksource_register_hz returned %d\n", err);
                return;
        }
-       clockevents_register_device(&itimer_clockevent);
+       clockevents_register_device(&timer_clockevent);
 }
 
 void read_persistent_clock(struct timespec *ts)
 {
-       long long nsecs = os_nsecs();
+       long long nsecs = os_persistent_clock_emulation();
 
        set_normalized_timespec(ts, nsecs / NSEC_PER_SEC,
                                nsecs % NSEC_PER_SEC);
@@ -110,6 +128,6 @@ void read_persistent_clock(struct timespec *ts)
 
 void __init time_init(void)
 {
-       timer_init();
-       late_time_init = setup_itimer;
+       timer_set_signal_handler();
+       late_time_init = timer_setup;
 }
diff --git a/arch/um/os-Linux/internal.h b/arch/um/os-Linux/internal.h
deleted file mode 100644
index 0dc2c9f..0000000
--- a/arch/um/os-Linux/internal.h
+++ /dev/null
@@ -1 +0,0 @@
-void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc);
diff --git a/arch/um/os-Linux/main.c b/arch/um/os-Linux/main.c
index df9191a..6e36f0f 100644
--- a/arch/um/os-Linux/main.c
+++ b/arch/um/os-Linux/main.c
@@ -163,13 +163,13 @@ int __init main(int argc, char **argv, char **envp)
 
        /*
         * This signal stuff used to be in the reboot case.  However,
-        * sometimes a SIGVTALRM can come in when we're halting (reproducably
+        * sometimes a timer signal can come in when we're halting (reproducably
         * when writing out gcov information, presumably because that takes
         * some time) and cause a segfault.
         */
 
-       /* stop timers and set SIGVTALRM to be ignored */
-       disable_timer();
+       /* stop timers and set timer signal to be ignored */
+       os_timer_disable();
 
        /* disable SIGIO for the fds and set SIGIO to be ignored */
        err = deactivate_all_fds();
diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c
index 8408aba..f3bd983 100644
--- a/arch/um/os-Linux/process.c
+++ b/arch/um/os-Linux/process.c
@@ -89,6 +89,11 @@ int os_process_parent(int pid)
        return parent;
 }
 
+void os_alarm_process(int pid)
+{
+       kill(pid, SIGALRM);
+}
+
 void os_stop_process(int pid)
 {
        kill(pid, SIGSTOP);
diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
index 7b605e4..4a9be55 100644
--- a/arch/um/os-Linux/signal.c
+++ b/arch/um/os-Linux/signal.c
@@ -13,7 +13,6 @@
 #include <kern_util.h>
 #include <os.h>
 #include <sysdep/mcontext.h>
-#include "internal.h"
 
 void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
        [SIGTRAP]       = relay_signal,
@@ -23,7 +22,8 @@ void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
        [SIGBUS]        = bus_handler,
        [SIGSEGV]       = segv_handler,
        [SIGIO]         = sigio_handler,
-       [SIGVTALRM]     = timer_handler };
+       [SIGALRM]       = timer_handler
+};
 
 static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
 {
@@ -38,7 +38,7 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
        }
 
        /* enable signals if sig isn't IRQ signal */
-       if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGVTALRM))
+       if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGALRM))
                unblock_signals();
 
        (*sig_info[sig])(sig, si, &r);
@@ -55,8 +55,8 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
 #define SIGIO_BIT 0
 #define SIGIO_MASK (1 << SIGIO_BIT)
 
-#define SIGVTALRM_BIT 1
-#define SIGVTALRM_MASK (1 << SIGVTALRM_BIT)
+#define SIGALRM_BIT 1
+#define SIGALRM_MASK (1 << SIGALRM_BIT)
 
 static int signals_enabled;
 static unsigned int signals_pending;
@@ -78,46 +78,47 @@ void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
        set_signals(enabled);
 }
 
-static void real_alarm_handler(mcontext_t *mc)
+static void timer_real_alarm_handler(mcontext_t *mc)
 {
        struct uml_pt_regs regs;
 
        if (mc != NULL)
                get_regs_from_mc(&regs, mc);
        regs.is_user = 0;
-       unblock_signals();
-       timer_handler(SIGVTALRM, NULL, &regs);
+       timer_handler(SIGALRM, NULL, &regs);
 }
 
-void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
+void timer_alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
 {
        int enabled;
 
        enabled = signals_enabled;
        if (!signals_enabled) {
-               signals_pending |= SIGVTALRM_MASK;
+               signals_pending |= SIGALRM_MASK;
                return;
        }
 
        block_signals();
-
-       real_alarm_handler(mc);
+       timer_real_alarm_handler(mc);
        set_signals(enabled);
 }
 
-void timer_init(void)
+void timer_set_signal_handler(void)
 {
-       set_handler(SIGVTALRM);
+       set_handler(SIGALRM);
 }
 
 void set_sigstack(void *sig_stack, int size)
 {
-       stack_t stack = ((stack_t) { .ss_flags  = 0,
-                                    .ss_sp     = (__ptr_t) sig_stack,
-                                    .ss_size   = size - sizeof(void *) });
+       stack_t stack = ((stack_t) {
+                   .ss_flags = 0,
+                               .ss_sp    = (__ptr_t) sig_stack,
+                               .ss_size  = size - sizeof(void *)
+       });
 
-       if (sigaltstack(&stack, NULL) != 0)
+       if (sigaltstack(&stack, NULL) != 0) {
                panic("enabling signal stack failed, errno = %d\n", errno);
+       }
 }
 
 static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
@@ -129,10 +130,9 @@ static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
 
        [SIGIO] = sig_handler,
        [SIGWINCH] = sig_handler,
-       [SIGVTALRM] = alarm_handler
+       [SIGALRM] = timer_alarm_handler
 };
 
-
 static void hard_handler(int sig, siginfo_t *si, void *p)
 {
        struct ucontext *uc = p;
@@ -186,9 +186,9 @@ void set_handler(int sig)
 
        /* block irq ones */
        sigemptyset(&action.sa_mask);
-       sigaddset(&action.sa_mask, SIGVTALRM);
        sigaddset(&action.sa_mask, SIGIO);
        sigaddset(&action.sa_mask, SIGWINCH);
+       sigaddset(&action.sa_mask, SIGALRM);
 
        if (sig == SIGSEGV)
                flags |= SA_NODEFER;
@@ -281,8 +281,8 @@ void unblock_signals(void)
                if (save_pending & SIGIO_MASK)
                        sig_handler_common(SIGIO, NULL, NULL);
 
-               if (save_pending & SIGVTALRM_MASK)
-                       real_alarm_handler(NULL);
+               if (save_pending & SIGALRM_MASK)
+                       timer_real_alarm_handler(NULL);
        }
 }
 
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index 7a97775..2caada3 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -45,7 +45,7 @@ static int ptrace_dump_regs(int pid)
  * Signals that are OK to receive in the stub - we'll just continue it.
  * SIGWINCH will happen when UML is inside a detached screen.
  */
-#define STUB_SIG_MASK ((1 << SIGVTALRM) | (1 << SIGWINCH))
+#define STUB_SIG_MASK ((1 << SIGALRM) | (1 << SIGWINCH))
 
 /* Signals that the stub will finish with - anything else is an error */
 #define STUB_DONE_MASK (1 << SIGTRAP)
@@ -179,19 +179,13 @@ extern int __syscall_stub_start;
 static int userspace_tramp(void *stack)
 {
        void *addr;
-       int err, fd;
+       int fd;
        unsigned long long offset;
 
        ptrace(PTRACE_TRACEME, 0, 0, 0);
 
        signal(SIGTERM, SIG_DFL);
        signal(SIGWINCH, SIG_IGN);
-       err = set_interval();
-       if (err) {
-               printk(UM_KERN_ERR "userspace_tramp - setting timer failed, "
-                      "errno = %d\n", err);
-               exit(1);
-       }
 
        /*
         * This has a pte, but it can't be mapped in with the usual
@@ -282,7 +276,7 @@ int start_userspace(unsigned long stub_stack)
                               "errno = %d\n", errno);
                        goto out_kill;
                }
-       } while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGVTALRM));
+       } while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGALRM));
 
        if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
                err = -EINVAL;
@@ -315,8 +309,6 @@ int start_userspace(unsigned long stub_stack)
 
 void userspace(struct uml_pt_regs *regs)
 {
-       struct itimerval timer;
-       unsigned long long nsecs, now;
        int err, status, op, pid = userspace_pid[0];
        /* To prevent races if using_sysemu changes under us.*/
        int local_using_sysemu;
@@ -325,13 +317,8 @@ void userspace(struct uml_pt_regs *regs)
        /* Handle any immediate reschedules or signals */
        interrupt_end();
 
-       if (getitimer(ITIMER_VIRTUAL, &timer))
-               printk(UM_KERN_ERR "Failed to get itimer, errno = %d\n", errno);
-       nsecs = timer.it_value.tv_sec * UM_NSEC_PER_SEC +
-               timer.it_value.tv_usec * UM_NSEC_PER_USEC;
-       nsecs += os_nsecs();
-
        while (1) {
+
                /*
                 * This can legitimately fail if the process loads a
                 * bogus value into a segment register.  It will
@@ -401,18 +388,7 @@ void userspace(struct uml_pt_regs *regs)
                        case SIGTRAP:
                                relay_signal(SIGTRAP, (struct siginfo *)&si, regs);
                                break;
-                       case SIGVTALRM:
-                               now = os_nsecs();
-                               if (now < nsecs)
-                                       break;
-                               block_signals();
-                               (*sig_info[sig])(sig, (struct siginfo *)&si, regs);
-                               unblock_signals();
-                               nsecs = timer.it_value.tv_sec *
-                                       UM_NSEC_PER_SEC +
-                                       timer.it_value.tv_usec *
-                                       UM_NSEC_PER_USEC;
-                               nsecs += os_nsecs();
+                       case SIGALRM:
                                break;
                        case SIGIO:
                        case SIGILL:
@@ -460,7 +436,6 @@ __initcall(init_thread_regs);
 
 int copy_context_skas0(unsigned long new_stack, int pid)
 {
-       struct timeval tv = { .tv_sec = 0, .tv_usec = UM_USEC_PER_SEC / UM_HZ };
        int err;
        unsigned long current_stack = current_stub_stack();
        struct stub_data *data = (struct stub_data *) current_stack;
@@ -472,11 +447,10 @@ int copy_context_skas0(unsigned long new_stack, int pid)
         * prepare offset and fd of child's stack as argument for parent's
         * and child's mmap2 calls
         */
-       *data = ((struct stub_data) { .offset   = MMAP_OFFSET(new_offset),
-                                     .fd       = new_fd,
-                                     .timer    = ((struct itimerval)
-                                                  { .it_value = tv,
-                                                    .it_interval = tv }) });
+       *data = ((struct stub_data) { 
+                       .offset = MMAP_OFFSET(new_offset),
+                       .fd     = new_fd
+       });
 
        err = ptrace_setregs(pid, thread_regs);
        if (err < 0) {
diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c
index e9824d5..0e2bb7d 100644
--- a/arch/um/os-Linux/time.c
+++ b/arch/um/os-Linux/time.c
@@ -1,4 +1,5 @@
 /*
+ * Copyright (C) 2012-2014 Cisco Systems
  * Copyright (C) 2000 - 2007 Jeff Dike (jdike{addtoit,linux.intel}.com)
  * Licensed under the GPL
  */
@@ -10,177 +11,172 @@
 #include <sys/time.h>
 #include <kern_util.h>
 #include <os.h>
-#include "internal.h"
+#include <string.h>
+#include <timer-internal.h>
 
-int set_interval(void)
-{
-       int usec = UM_USEC_PER_SEC / UM_HZ;
-       struct itimerval interval = ((struct itimerval) { { 0, usec },
-                                                         { 0, usec } });
-
-       if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
-               return -errno;
+static timer_t event_high_res_timer = 0;
 
-       return 0;
+static inline long long timeval_to_ns(const struct timeval *tv)
+{
+       return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
+               tv->tv_usec * UM_NSEC_PER_USEC;
 }
 
-int timer_one_shot(int ticks)
+static inline long long timespec_to_ns(const struct timespec *ts)
 {
-       unsigned long usec = ticks * UM_USEC_PER_SEC / UM_HZ;
-       unsigned long sec = usec / UM_USEC_PER_SEC;
-       struct itimerval interval;
-
-       usec %= UM_USEC_PER_SEC;
-       interval = ((struct itimerval) { { 0, 0 }, { sec, usec } });
+       return ((long long) ts->tv_sec * UM_NSEC_PER_SEC) +
+               ts->tv_nsec;
+}
 
-       if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
-               return -errno;
+long long os_persistent_clock_emulation (void) {
+       struct timespec realtime_tp;
 
-       return 0;
+       clock_gettime(CLOCK_REALTIME, &realtime_tp);
+       return timespec_to_ns(&realtime_tp);
 }
 
 /**
- * timeval_to_ns - Convert timeval to nanoseconds
- * @ts:                pointer to the timeval variable to be converted
- *
- * Returns the scalar nanosecond representation of the timeval
- * parameter.
- *
- * Ripped from linux/time.h because it's a kernel header, and thus
- * unusable from here.
+ * os_timer_create() - create an new posix (interval) timer
  */
-static inline long long timeval_to_ns(const struct timeval *tv)
-{
-       return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
-               tv->tv_usec * UM_NSEC_PER_USEC;
+int os_timer_create(void* timer) {
+
+       timer_t* t = timer;
+
+       if(t == NULL) {
+               t = &event_high_res_timer;
+       }
+
+       if (timer_create(
+               CLOCK_MONOTONIC,
+               NULL,
+               t) == -1) {
+               return -1;
+       }
+       return 0;
 }
 
-long long disable_timer(void)
+int os_timer_set_interval(void* timer, void* i)
 {
-       struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } });
-       long long remain, max = UM_NSEC_PER_SEC / UM_HZ;
+       struct itimerspec its;
+       unsigned long long nsec;
+       timer_t* t = timer;
+       struct itimerspec* its_in = i;
 
-       if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0)
-               printk(UM_KERN_ERR "disable_timer - setitimer failed, "
-                      "errno = %d\n", errno);
+       if(t == NULL) {
+               t = &event_high_res_timer;
+       }
 
-       remain = timeval_to_ns(&time.it_value);
-       if (remain > max)
-               remain = max;
+       nsec = UM_NSEC_PER_SEC / UM_HZ;
 
-       return remain;
-}
+       if(its_in != NULL) {
+               its.it_value.tv_sec = its_in->it_value.tv_sec;
+               its.it_value.tv_nsec = its_in->it_value.tv_nsec;
+       } else {
+               its.it_value.tv_sec = 0;
+               its.it_value.tv_nsec = nsec;
+       }
 
-long long os_nsecs(void)
-{
-       struct timeval tv;
+       its.it_interval.tv_sec = 0;
+       its.it_interval.tv_nsec = nsec;
 
-       gettimeofday(&tv, NULL);
-       return timeval_to_ns(&tv);
-}
+       if(timer_settime(*t, 0, &its, NULL) == -1) {
+               return -errno;
+       }
 
-#ifdef UML_CONFIG_NO_HZ_COMMON
-static int after_sleep_interval(struct timespec *ts)
-{
        return 0;
 }
 
-static void deliver_alarm(void)
+/**
+ * os_timer_remain() - returns the remaining nano seconds of the given interval
+ *                     timer
+ * Because this is the remaining time of an interval timer, which correspondends
+ * to HZ, this value can never be bigger than one second. Just
+ * the nanosecond part of the timer is returned.
+ * The returned time is relative to the start time of the interval timer.
+ * Return an negative value in an error case.
+ */
+long os_timer_remain(void* timer)
 {
-       alarm_handler(SIGVTALRM, NULL, NULL);
-}
+       struct itimerspec its;
+       timer_t* t = timer;
 
-static unsigned long long sleep_time(unsigned long long nsecs)
-{
-       return nsecs;
-}
+       if(t == NULL) {
+               t = &event_high_res_timer;
+       }
 
-#else
-unsigned long long last_tick;
-unsigned long long skew;
+       if(timer_gettime(t, &its) == -1) {
+               return -errno;
+       }
+
+       return its.it_value.tv_nsec;
+}
 
-static void deliver_alarm(void)
+int os_timer_one_shot(int ticks)
 {
-       unsigned long long this_tick = os_nsecs();
-       int one_tick = UM_NSEC_PER_SEC / UM_HZ;
+       struct itimerspec its;
+       unsigned long long nsec;
+       unsigned long sec;
 
-       /* Protection against the host's time going backwards */
-       if ((last_tick != 0) && (this_tick < last_tick))
-               this_tick = last_tick;
+    nsec = (ticks + 1);
+    sec = nsec / UM_NSEC_PER_SEC;
+       nsec = nsec % UM_NSEC_PER_SEC;
 
-       if (last_tick == 0)
-               last_tick = this_tick - one_tick;
+       its.it_value.tv_sec = nsec / UM_NSEC_PER_SEC;
+       its.it_value.tv_nsec = nsec;
 
-       skew += this_tick - last_tick;
+       its.it_interval.tv_sec = 0;
+       its.it_interval.tv_nsec = 0; // we cheat here
 
-       while (skew >= one_tick) {
-               alarm_handler(SIGVTALRM, NULL, NULL);
-               skew -= one_tick;
-       }
-
-       last_tick = this_tick;
+       timer_settime(event_high_res_timer, 0, &its, NULL);
+       return 0;
 }
 
-static unsigned long long sleep_time(unsigned long long nsecs)
+/**
+ * os_timer_disable() - disable the posix (interval) timer
+ * Returns the remaining interval timer time in nanoseconds
+ */
+long long os_timer_disable(void)
 {
-       return nsecs > skew ? nsecs - skew : 0;
+       struct itimerspec its;
+
+       memset(&its, 0, sizeof(struct itimerspec));
+       timer_settime(event_high_res_timer, 0, &its, &its);
+
+       return its.it_value.tv_sec * UM_NSEC_PER_SEC + its.it_value.tv_nsec;
 }
 
-static inline long long timespec_to_us(const struct timespec *ts)
+long long os_vnsecs(void)
 {
-       return ((long long) ts->tv_sec * UM_USEC_PER_SEC) +
-               ts->tv_nsec / UM_NSEC_PER_USEC;
+       struct timespec ts;
+
+       clock_gettime(CLOCK_PROCESS_CPUTIME_ID,&ts);
+       return timespec_to_ns(&ts);
 }
 
-static int after_sleep_interval(struct timespec *ts)
+long long os_nsecs(void)
 {
-       int usec = UM_USEC_PER_SEC / UM_HZ;
-       long long start_usecs = timespec_to_us(ts);
-       struct timeval tv;
-       struct itimerval interval;
-
-       /*
-        * It seems that rounding can increase the value returned from
-        * setitimer to larger than the one passed in.  Over time,
-        * this will cause the remaining time to be greater than the
-        * tick interval.  If this happens, then just reduce the first
-        * tick to the interval value.
-        */
-       if (start_usecs > usec)
-               start_usecs = usec;
-
-       start_usecs -= skew / UM_NSEC_PER_USEC;
-       if (start_usecs < 0)
-               start_usecs = 0;
-
-       tv = ((struct timeval) { .tv_sec  = start_usecs / UM_USEC_PER_SEC,
-                                .tv_usec = start_usecs % UM_USEC_PER_SEC });
-       interval = ((struct itimerval) { { 0, usec }, tv });
-
-       if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
-               return -errno;
+       struct timespec ts;
 
-       return 0;
+       clock_gettime(CLOCK_MONOTONIC,&ts);
+       return timespec_to_ns(&ts);
 }
-#endif
 
-void idle_sleep(unsigned long long nsecs)
+/**
+ * os_idle_sleep() - sleep for a given time of nsecs
+ * @nsecs: nanoseconds to sleep
+ */
+void os_idle_sleep(unsigned long long nsecs)
 {
        struct timespec ts;
 
-       /*
-        * nsecs can come in as zero, in which case, this starts a
-        * busy loop.  To prevent this, reset nsecs to the tick
-        * interval if it is zero.
-        */
-       if (nsecs == 0)
-               nsecs = UM_NSEC_PER_SEC / UM_HZ;
-
-       nsecs = sleep_time(nsecs);
-       ts = ((struct timespec) { .tv_sec       = nsecs / UM_NSEC_PER_SEC,
-                                 .tv_nsec      = nsecs % UM_NSEC_PER_SEC });
-
-       if (nanosleep(&ts, &ts) == 0)
-               deliver_alarm();
-       after_sleep_interval(&ts);
+       if (nsecs <= 0) {
+               return;
+       }
+
+       ts = ((struct timespec) {
+                       .tv_sec  = nsecs / UM_NSEC_PER_SEC,
+                       .tv_nsec = nsecs % UM_NSEC_PER_SEC
+       });
+
+       clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, NULL);
 }
-- 
2.4.1


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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Anton Ivanov]

I will give it a spin before the end of the weekend and run the full 
test suite on it.

A.

[snip]

>> Cascading the kernel timer looks like the correct solution.
> Hi,
>
> below patch get's rid of all userspace timers.
> When a kernel timer interrupt is received the userspace process of the
> corresponding task is signaled via SIGALRM.
> The SIGALRM signal forces the userspace process to go back into
> userspace() function. There the SIGALRM signal is ignored as the
> interrupt was already processed anyway by the uml kernel.
>
> what do you think about this approach?
>
> Can you give this patch a try
>
> with kind regards
> thomas
>
>
[snip]


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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Thomas Meyer]

Am Donnerstag, den 04.06.2015, 12:04 +0200 schrieb Thomas Meyer:
> 
> Hi,
> 
> below patch get's rid of all userspace timers.
> When a kernel timer interrupt is received the userspace process of 
> the
> corresponding task is signaled via SIGALRM.
> The SIGALRM signal forces the userspace process to go back into
> userspace() function. There the SIGALRM signal is ignored as the
> interrupt was already processed anyway by the uml kernel.
> 
> what do you think about this approach?
> 
> Can you give this patch a try

Hi,

I see a hang in copy_context_skas0().
I think this is because the stub code is executing and timer interrupts
are still enabled.

The timer interrupt will signal the process (==from_mm) which is now in
the stub_clone_handler() (see also init_thread_regs()).

So any ideas how to avoid signaling userspace process currently in
stub_clone_handler()? would it be an option to disable interrupts
before copy_context_skas0()?

Richard, what do you think?

with regards
thomas

> 
> with kind regards
> thomas
> 
> diff --git a/arch/um/Makefile b/arch/um/Makefile
> index 17d4460..a4a434f 100644
> --- a/arch/um/Makefile
> +++ b/arch/um/Makefile
> @@ -130,7 +130,7 @@ export LDS_ELF_FORMAT := $(ELF_FORMAT)
>  # The wrappers will select whether using "malloc" or the kernel 
> allocator.
>  LINK_WRAPS = -Wl,--wrap,malloc -Wl,--wrap,free -Wl,--wrap,calloc
>  
> -LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt))
> +LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt)) -lrt
>  
>  # Used by link-vmlinux.sh which has special support for um link
>  export CFLAGS_vmlinux := $(LINK-y) $(LINK_WRAPS) $(LD_FLAGS_CMDLINE)
> diff --git a/arch/um/include/shared/os.h 
> b/arch/um/include/shared/os.h
> index d824528..8f8f5d7 100644
> --- a/arch/um/include/shared/os.h
> +++ b/arch/um/include/shared/os.h
> @@ -183,6 +183,7 @@ extern int create_mem_file(unsigned long long 
> len);
>  /* process.c */
>  extern unsigned long os_process_pc(int pid);
>  extern int os_process_parent(int pid);
> +extern void os_alarm_process(int pid);
>  extern void os_stop_process(int pid);
>  extern void os_kill_process(int pid, int reap_child);
>  extern void os_kill_ptraced_process(int pid, int reap_child);
> @@ -217,7 +218,7 @@ extern int set_umid(char *name);
>  extern char *get_umid(void);
>  
>  /* signal.c */
> -extern void timer_init(void);
> +extern void timer_set_signal_handler(void);
>  extern void set_sigstack(void *sig_stack, int size);
>  extern void remove_sigstack(void);
>  extern void set_handler(int sig);
> @@ -238,12 +239,16 @@ extern void um_early_printk(const char *s, 
> unsigned int n);
>  extern void os_fix_helper_signals(void);
>  
>  /* time.c */
> -extern void idle_sleep(unsigned long long nsecs);
> -extern int set_interval(void);
> -extern int timer_one_shot(int ticks);
> -extern long long disable_timer(void);
> +extern void os_idle_sleep(unsigned long long nsecs);
> +extern int os_timer_create(void* timer);
> +extern int os_timer_set_interval(void* timer, void* its);
> +extern int os_timer_one_shot(int ticks);
> +extern long long os_timer_disable(void);
> +extern long os_timer_remain(void* timer);
>  extern void uml_idle_timer(void);
> +extern long long os_persistent_clock_emulation(void);
>  extern long long os_nsecs(void);
> +extern long long os_vnsecs(void);
>  
>  /* skas/mem.c */
>  extern long run_syscall_stub(struct mm_id * mm_idp,
> diff --git a/arch/um/include/shared/skas/stub-data.h 
> b/arch/um/include/shared/skas/stub-data.h
> index f6ed92c..e09d8fd 100644
> --- a/arch/um/include/shared/skas/stub-data.h
> +++ b/arch/um/include/shared/skas/stub-data.h
> @@ -6,12 +6,11 @@
>  #ifndef __STUB_DATA_H
>  #define __STUB_DATA_H
>  
> -#include <sys/time.h>
> +#include <time.h>
>  
>  struct stub_data {
> -       long offset;
> +       unsigned long offset;
>         int fd;
> -       struct itimerval timer;
>         long err;
>  };
>  
> diff --git a/arch/um/include/shared/timer-internal.h 
> b/arch/um/include/shared/timer-internal.h
> new file mode 100644
> index 0000000..03e6f21
> --- /dev/null
> +++ b/arch/um/include/shared/timer-internal.h
> @@ -0,0 +1,13 @@
> +/*
> + * Copyright (C) 2012 - 2014 Cisco Systems
> + * Copyright (C) 2000 - 2007 Jeff Dike 
> (jdike@{addtoit,linux.intel}.com)
> + * Licensed under the GPL
> + */
> +
> +#ifndef __TIMER_INTERNAL_H__
> +#define __TIMER_INTERNAL_H__
> +
> +#define TIMER_MULTIPLIER 256
> +#define TIMER_MIN_DELTA  500
> +
> +#endif
> diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
> index 68b9119..2ce38c1 100644
> --- a/arch/um/kernel/process.c
> +++ b/arch/um/kernel/process.c
> @@ -27,6 +27,7 @@
>  #include <kern_util.h>
>  #include <os.h>
>  #include <skas.h>
> +#include <timer-internal.h>
>  
>  /*
>   * This is a per-cpu array.  A processor only modifies its entry and 
> it only
> @@ -201,11 +202,8 @@ void initial_thread_cb(void (*proc)(void *), 
> void *arg)
>  
>  void arch_cpu_idle(void)
>  {
> -       unsigned long long nsecs;
> -
>         cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
> -       nsecs = disable_timer();
> -       idle_sleep(nsecs);
> +       os_idle_sleep(UM_NSEC_PER_SEC);
>         local_irq_enable();
>  }
>  
> diff --git a/arch/um/kernel/skas/clone.c 
> b/arch/um/kernel/skas/clone.c
> index 289771d..498148b 100644
> --- a/arch/um/kernel/skas/clone.c
> +++ b/arch/um/kernel/skas/clone.c
> @@ -35,11 +35,6 @@ stub_clone_handler(void)
>         if (err)
>                 goto out;
>  
> -       err = stub_syscall3(__NR_setitimer, ITIMER_VIRTUAL,
> -                           (long) &data->timer, 0);
> -       if (err)
> -               goto out;
> -
>         remap_stack(data->fd, data->offset);
>         goto done;
>  
> diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c
> index 117568d..29f1125 100644
> --- a/arch/um/kernel/time.c
> +++ b/arch/um/kernel/time.c
> @@ -1,4 +1,5 @@
>  /*
> + * Copyright (C) 2012-2014 Cisco Systems
>   * Copyright (C) 2000 - 2007 Jeff Dike 
> (jdike@{addtoit,linux.intel}.com)
>   * Licensed under the GPL
>   */
> @@ -7,11 +8,15 @@
>  #include <linux/init.h>
>  #include <linux/interrupt.h>
>  #include <linux/jiffies.h>
> +#include <linux/mm.h>
> +#include <linux/sched.h>
> +#include <linux/spinlock.h>
>  #include <linux/threads.h>
>  #include <asm/irq.h>
>  #include <asm/param.h>
>  #include <kern_util.h>
>  #include <os.h>
> +#include <timer-internal.h>
>  
>  void timer_handler(int sig, struct siginfo *unused_si, struct 
> uml_pt_regs *regs)
>  {
> @@ -22,18 +27,20 @@ void timer_handler(int sig, struct siginfo 
> *unused_si, struct uml_pt_regs *regs)
>         local_irq_restore(flags);
>  }
>  
> -static void itimer_set_mode(enum clock_event_mode mode,
> +static void timer_set_mode(enum clock_event_mode mode,
>                             struct clock_event_device *evt)
>  {
>         switch (mode) {
>         case CLOCK_EVT_MODE_PERIODIC:
> -               set_interval();
> +               os_timer_set_interval(NULL, NULL);
>                 break;
>  
> +       case CLOCK_EVT_MODE_ONESHOT:
> +               os_timer_one_shot(1);
> +
>         case CLOCK_EVT_MODE_SHUTDOWN:
>         case CLOCK_EVT_MODE_UNUSED:
> -       case CLOCK_EVT_MODE_ONESHOT:
> -               disable_timer();
> +               os_timer_disable();
>                 break;
>  
>         case CLOCK_EVT_MODE_RESUME:
> @@ -41,68 +48,79 @@ static void itimer_set_mode(enum clock_event_mode 
> mode,
>         }
>  }
>  
> -static int itimer_next_event(unsigned long delta,
> +static int timer_next_event(unsigned long delta,
>                              struct clock_event_device *evt)
>  {
> -       return timer_one_shot(delta + 1);
> +       return os_timer_one_shot(delta);
>  }
>  
> -static struct clock_event_device itimer_clockevent = {
> -       .name           = "itimer",
> +static struct clock_event_device timer_clockevent = {
> +       .name           = "posix-timer",
>         .rating         = 250,
>         .cpumask        = cpu_all_mask,
>         .features       = CLOCK_EVT_FEAT_PERIODIC | 
> CLOCK_EVT_FEAT_ONESHOT,
> -       .set_mode       = itimer_set_mode,
> -       .set_next_event = itimer_next_event,
> -       .shift          = 32,
> +       .set_mode       = timer_set_mode,
> +       .set_next_event = timer_next_event,
> +       .shift          = 0,
> +       .max_delta_ns   = 0xffffffff,
> +       .min_delta_ns   = TIMER_MIN_DELTA, //microsecond resolution 
> should be enough for anyone, same as 640K RAM
>         .irq            = 0,
> +       .mult           = 1,
>  };
>  
> -static irqreturn_t um_timer(int irq, void *dev)
> +static irqreturn_t um_timer_irq(int irq, void *dev)
>  {
> -       (*itimer_clockevent.event_handler)(&itimer_clockevent);
> +       if (get_current()->mm != NULL)
> +       {
> +               os_alarm_process(get_current()->mm
> ->context.id.u.pid);
> +       }
> +
> +       (*timer_clockevent.event_handler)(&timer_clockevent);
>  
>         return IRQ_HANDLED;
>  }
>  
> -static cycle_t itimer_read(struct clocksource *cs)
> +static cycle_t timer_read(struct clocksource *cs)
>  {
> -       return os_nsecs() / 1000;
> +       return os_nsecs() / TIMER_MULTIPLIER;
>  }
>  
> -static struct clocksource itimer_clocksource = {
> -       .name           = "itimer",
> +static struct clocksource timer_clocksource = {
> +       .name           = "timer",
>         .rating         = 300,
> -       .read           = itimer_read,
> +       .read           = timer_read,
>         .mask           = CLOCKSOURCE_MASK(64),
>         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
>  };
>  
> -static void __init setup_itimer(void)
> +static void __init timer_setup(void)
>  {
>         int err;
>  
> -       err = request_irq(TIMER_IRQ, um_timer, 0, "timer", NULL);
> -       if (err != 0)
> +       err = request_irq(TIMER_IRQ, um_timer_irq, IRQF_TIMER, "hr 
> timer", NULL);
> +       if (err != 0) {
>                 printk(KERN_ERR "register_timer : request_irq failed 
> - "
>                        "errno = %d\n", -err);
> +               return;
> +    }
> +
> +    err = os_timer_create(NULL);
> +    if (err != 0) {
> +        printk(KERN_ERR "creation of timer failed - errno = %d\n", 
> -err);
> +        return;
> +    }
>  
> -       itimer_clockevent.mult = div_sc(HZ, NSEC_PER_SEC, 32);
> -       itimer_clockevent.max_delta_ns =
> -               clockevent_delta2ns(60 * HZ, &itimer_clockevent);
> -       itimer_clockevent.min_delta_ns =
> -               clockevent_delta2ns(1, &itimer_clockevent);
> -       err = clocksource_register_hz(&itimer_clocksource, 
> USEC_PER_SEC);
> +       err = clocksource_register_hz(&timer_clocksource, 
> NSEC_PER_SEC/TIMER_MULTIPLIER);
>         if (err) {
>                 printk(KERN_ERR "clocksource_register_hz returned 
> %d\n", err);
>                 return;
>         }
> -       clockevents_register_device(&itimer_clockevent);
> +       clockevents_register_device(&timer_clockevent);
>  }
>  
>  void read_persistent_clock(struct timespec *ts)
>  {
> -       long long nsecs = os_nsecs();
> +       long long nsecs = os_persistent_clock_emulation();
>  
>         set_normalized_timespec(ts, nsecs / NSEC_PER_SEC,
>                                 nsecs % NSEC_PER_SEC);
> @@ -110,6 +128,6 @@ void read_persistent_clock(struct timespec *ts)
>  
>  void __init time_init(void)
>  {
> -       timer_init();
> -       late_time_init = setup_itimer;
> +       timer_set_signal_handler();
> +       late_time_init = timer_setup;
>  }
> diff --git a/arch/um/os-Linux/internal.h b/arch/um/os
> -Linux/internal.h
> deleted file mode 100644
> index 0dc2c9f..0000000
> --- a/arch/um/os-Linux/internal.h
> +++ /dev/null
> @@ -1 +0,0 @@
> -void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t 
> *mc);
> diff --git a/arch/um/os-Linux/main.c b/arch/um/os-Linux/main.c
> index df9191a..6e36f0f 100644
> --- a/arch/um/os-Linux/main.c
> +++ b/arch/um/os-Linux/main.c
> @@ -163,13 +163,13 @@ int __init main(int argc, char **argv, char 
> **envp)
>  
>         /*
>          * This signal stuff used to be in the reboot case.  However,
> -        * sometimes a SIGVTALRM can come in when we're halting 
> (reproducably
> +        * sometimes a timer signal can come in when we're halting 
> (reproducably
>          * when writing out gcov information, presumably because that 
> takes
>          * some time) and cause a segfault.
>          */
>  
> -       /* stop timers and set SIGVTALRM to be ignored */
> -       disable_timer();
> +       /* stop timers and set timer signal to be ignored */
> +       os_timer_disable();
>  
>         /* disable SIGIO for the fds and set SIGIO to be ignored */
>         err = deactivate_all_fds();
> diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c
> index 8408aba..f3bd983 100644
> --- a/arch/um/os-Linux/process.c
> +++ b/arch/um/os-Linux/process.c
> @@ -89,6 +89,11 @@ int os_process_parent(int pid)
>         return parent;
>  }
>  
> +void os_alarm_process(int pid)
> +{
> +       kill(pid, SIGALRM);
> +}
> +
>  void os_stop_process(int pid)
>  {
>         kill(pid, SIGSTOP);
> diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
> index 7b605e4..4a9be55 100644
> --- a/arch/um/os-Linux/signal.c
> +++ b/arch/um/os-Linux/signal.c
> @@ -13,7 +13,6 @@
>  #include <kern_util.h>
>  #include <os.h>
>  #include <sysdep/mcontext.h>
> -#include "internal.h"
>  
>  void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) 
> = {
>         [SIGTRAP]       = relay_signal,
> @@ -23,7 +22,8 @@ void (*sig_info[NSIG])(int, struct siginfo *, 
> struct uml_pt_regs *) = {
>         [SIGBUS]        = bus_handler,
>         [SIGSEGV]       = segv_handler,
>         [SIGIO]         = sigio_handler,
> -       [SIGVTALRM]     = timer_handler };
> +       [SIGALRM]       = timer_handler
> +};
>  
>  static void sig_handler_common(int sig, struct siginfo *si, 
> mcontext_t *mc)
>  {
> @@ -38,7 +38,7 @@ static void sig_handler_common(int sig, struct 
> siginfo *si, mcontext_t *mc)
>         }
>  
>         /* enable signals if sig isn't IRQ signal */
> -       if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != 
> SIGVTALRM))
> +       if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGALRM))
>                 unblock_signals();
>  
>         (*sig_info[sig])(sig, si, &r);
> @@ -55,8 +55,8 @@ static void sig_handler_common(int sig, struct 
> siginfo *si, mcontext_t *mc)
>  #define SIGIO_BIT 0
>  #define SIGIO_MASK (1 << SIGIO_BIT)
>  
> -#define SIGVTALRM_BIT 1
> -#define SIGVTALRM_MASK (1 << SIGVTALRM_BIT)
> +#define SIGALRM_BIT 1
> +#define SIGALRM_MASK (1 << SIGALRM_BIT)
>  
>  static int signals_enabled;
>  static unsigned int signals_pending;
> @@ -78,46 +78,47 @@ void sig_handler(int sig, struct siginfo *si, 
> mcontext_t *mc)
>         set_signals(enabled);
>  }
>  
> -static void real_alarm_handler(mcontext_t *mc)
> +static void timer_real_alarm_handler(mcontext_t *mc)
>  {
>         struct uml_pt_regs regs;
>  
>         if (mc != NULL)
>                 get_regs_from_mc(&regs, mc);
>         regs.is_user = 0;
> -       unblock_signals();
> -       timer_handler(SIGVTALRM, NULL, &regs);
> +       timer_handler(SIGALRM, NULL, &regs);
>  }
>  
> -void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t 
> *mc)
> +void timer_alarm_handler(int sig, struct siginfo *unused_si, 
> mcontext_t *mc)
>  {
>         int enabled;
>  
>         enabled = signals_enabled;
>         if (!signals_enabled) {
> -               signals_pending |= SIGVTALRM_MASK;
> +               signals_pending |= SIGALRM_MASK;
>                 return;
>         }
>  
>         block_signals();
> -
> -       real_alarm_handler(mc);
> +       timer_real_alarm_handler(mc);
>         set_signals(enabled);
>  }
>  
> -void timer_init(void)
> +void timer_set_signal_handler(void)
>  {
> -       set_handler(SIGVTALRM);
> +       set_handler(SIGALRM);
>  }
>  
>  void set_sigstack(void *sig_stack, int size)
>  {
> -       stack_t stack = ((stack_t) { .ss_flags  = 0,
> -                                    .ss_sp     = (__ptr_t) 
> sig_stack,
> -                                    .ss_size   = size - sizeof(void 
> *) });
> +       stack_t stack = ((stack_t) {
> +                   .ss_flags = 0,
> +                               .ss_sp    = (__ptr_t) sig_stack,
> +                               .ss_size  = size - sizeof(void *)
> +       });
>  
> -       if (sigaltstack(&stack, NULL) != 0)
> +       if (sigaltstack(&stack, NULL) != 0) {
>                 panic("enabling signal stack failed, errno = %d\n", 
> errno);
> +       }
>  }
>  
>  static void (*handlers[_NSIG])(int sig, struct siginfo *si, 
> mcontext_t *mc) = {
> @@ -129,10 +130,9 @@ static void (*handlers[_NSIG])(int sig, struct 
> siginfo *si, mcontext_t *mc) = {
>  
>         [SIGIO] = sig_handler,
>         [SIGWINCH] = sig_handler,
> -       [SIGVTALRM] = alarm_handler
> +       [SIGALRM] = timer_alarm_handler
>  };
>  
> -
>  static void hard_handler(int sig, siginfo_t *si, void *p)
>  {
>         struct ucontext *uc = p;
> @@ -186,9 +186,9 @@ void set_handler(int sig)
>  
>         /* block irq ones */
>         sigemptyset(&action.sa_mask);
> -       sigaddset(&action.sa_mask, SIGVTALRM);
>         sigaddset(&action.sa_mask, SIGIO);
>         sigaddset(&action.sa_mask, SIGWINCH);
> +       sigaddset(&action.sa_mask, SIGALRM);
>  
>         if (sig == SIGSEGV)
>                 flags |= SA_NODEFER;
> @@ -281,8 +281,8 @@ void unblock_signals(void)
>                 if (save_pending & SIGIO_MASK)
>                         sig_handler_common(SIGIO, NULL, NULL);
>  
> -               if (save_pending & SIGVTALRM_MASK)
> -                       real_alarm_handler(NULL);
> +               if (save_pending & SIGALRM_MASK)
> +                       timer_real_alarm_handler(NULL);
>         }
>  }
>  
> diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os
> -Linux/skas/process.c
> index 7a97775..2caada3 100644
> --- a/arch/um/os-Linux/skas/process.c
> +++ b/arch/um/os-Linux/skas/process.c
> @@ -45,7 +45,7 @@ static int ptrace_dump_regs(int pid)
>   * Signals that are OK to receive in the stub - we'll just continue 
> it.
>   * SIGWINCH will happen when UML is inside a detached screen.
>   */
> -#define STUB_SIG_MASK ((1 << SIGVTALRM) | (1 << SIGWINCH))
> +#define STUB_SIG_MASK ((1 << SIGALRM) | (1 << SIGWINCH))
>  
>  /* Signals that the stub will finish with - anything else is an 
> error */
>  #define STUB_DONE_MASK (1 << SIGTRAP)
> @@ -179,19 +179,13 @@ extern int __syscall_stub_start;
>  static int userspace_tramp(void *stack)
>  {
>         void *addr;
> -       int err, fd;
> +       int fd;
>         unsigned long long offset;
>  
>         ptrace(PTRACE_TRACEME, 0, 0, 0);
>  
>         signal(SIGTERM, SIG_DFL);
>         signal(SIGWINCH, SIG_IGN);
> -       err = set_interval();
> -       if (err) {
> -               printk(UM_KERN_ERR "userspace_tramp - setting timer 
> failed, "
> -                      "errno = %d\n", err);
> -               exit(1);
> -       }
>  
>         /*
>          * This has a pte, but it can't be mapped in with the usual
> @@ -282,7 +276,7 @@ int start_userspace(unsigned long stub_stack)
>                                "errno = %d\n", errno);
>                         goto out_kill;
>                 }
> -       } while (WIFSTOPPED(status) && (WSTOPSIG(status) == 
> SIGVTALRM));
> +       } while (WIFSTOPPED(status) && (WSTOPSIG(status) == 
> SIGALRM));
>  
>         if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
>                 err = -EINVAL;
> @@ -315,8 +309,6 @@ int start_userspace(unsigned long stub_stack)
>  
>  void userspace(struct uml_pt_regs *regs)
>  {
> -       struct itimerval timer;
> -       unsigned long long nsecs, now;
>         int err, status, op, pid = userspace_pid[0];
>         /* To prevent races if using_sysemu changes under us.*/
>         int local_using_sysemu;
> @@ -325,13 +317,8 @@ void userspace(struct uml_pt_regs *regs)
>         /* Handle any immediate reschedules or signals */
>         interrupt_end();
>  
> -       if (getitimer(ITIMER_VIRTUAL, &timer))
> -               printk(UM_KERN_ERR "Failed to get itimer, errno = 
> %d\n", errno);
> -       nsecs = timer.it_value.tv_sec * UM_NSEC_PER_SEC +
> -               timer.it_value.tv_usec * UM_NSEC_PER_USEC;
> -       nsecs += os_nsecs();
> -
>         while (1) {
> +
>                 /*
>                  * This can legitimately fail if the process loads a
>                  * bogus value into a segment register.  It will
> @@ -401,18 +388,7 @@ void userspace(struct uml_pt_regs *regs)
>                         case SIGTRAP:
>                                 relay_signal(SIGTRAP, (struct siginfo 
> *)&si, regs);
>                                 break;
> -                       case SIGVTALRM:
> -                               now = os_nsecs();
> -                               if (now < nsecs)
> -                                       break;
> -                               block_signals();
> -                               (*sig_info[sig])(sig, (struct siginfo 
> *)&si, regs);
> -                               unblock_signals();
> -                               nsecs = timer.it_value.tv_sec *
> -                                       UM_NSEC_PER_SEC +
> -                                       timer.it_value.tv_usec *
> -                                       UM_NSEC_PER_USEC;
> -                               nsecs += os_nsecs();
> +                       case SIGALRM:
>                                 break;
>                         case SIGIO:
>                         case SIGILL:
> @@ -460,7 +436,6 @@ __initcall(init_thread_regs);
>  
>  int copy_context_skas0(unsigned long new_stack, int pid)
>  {
> -       struct timeval tv = { .tv_sec = 0, .tv_usec = UM_USEC_PER_SEC 
> / UM_HZ };
>         int err;
>         unsigned long current_stack = current_stub_stack();
>         struct stub_data *data = (struct stub_data *) current_stack;
> @@ -472,11 +447,10 @@ int copy_context_skas0(unsigned long new_stack, 
> int pid)
>          * prepare offset and fd of child's stack as argument for 
> parent's
>          * and child's mmap2 calls
>          */
> -       *data = ((struct stub_data) { .offset   = 
> MMAP_OFFSET(new_offset),
> -                                     .fd       = new_fd,
> -                                     .timer    = ((struct itimerval)
> -                                                  { .it_value = tv,
> -                                                    .it_interval = 
> tv }) });
> +       *data = ((struct stub_data) { 
> +                       .offset = MMAP_OFFSET(new_offset),
> +                       .fd     = new_fd
> +       });
>  
>         err = ptrace_setregs(pid, thread_regs);
>         if (err < 0) {
> diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c
> index e9824d5..0e2bb7d 100644
> --- a/arch/um/os-Linux/time.c
> +++ b/arch/um/os-Linux/time.c
> @@ -1,4 +1,5 @@
>  /*
> + * Copyright (C) 2012-2014 Cisco Systems
>   * Copyright (C) 2000 - 2007 Jeff Dike 
> (jdike{addtoit,linux.intel}.com)
>   * Licensed under the GPL
>   */
> @@ -10,177 +11,172 @@
>  #include <sys/time.h>
>  #include <kern_util.h>
>  #include <os.h>
> -#include "internal.h"
> +#include <string.h>
> +#include <timer-internal.h>
>  
> -int set_interval(void)
> -{
> -       int usec = UM_USEC_PER_SEC / UM_HZ;
> -       struct itimerval interval = ((struct itimerval) { { 0, usec 
> },
> -                                                         { 0, usec } 
> });
> -
> -       if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
> -               return -errno;
> +static timer_t event_high_res_timer = 0;
>  
> -       return 0;
> +static inline long long timeval_to_ns(const struct timeval *tv)
> +{
> +       return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
> +               tv->tv_usec * UM_NSEC_PER_USEC;
>  }
>  
> -int timer_one_shot(int ticks)
> +static inline long long timespec_to_ns(const struct timespec *ts)
>  {
> -       unsigned long usec = ticks * UM_USEC_PER_SEC / UM_HZ;
> -       unsigned long sec = usec / UM_USEC_PER_SEC;
> -       struct itimerval interval;
> -
> -       usec %= UM_USEC_PER_SEC;
> -       interval = ((struct itimerval) { { 0, 0 }, { sec, usec } });
> +       return ((long long) ts->tv_sec * UM_NSEC_PER_SEC) +
> +               ts->tv_nsec;
> +}
>  
> -       if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
> -               return -errno;
> +long long os_persistent_clock_emulation (void) {
> +       struct timespec realtime_tp;
>  
> -       return 0;
> +       clock_gettime(CLOCK_REALTIME, &realtime_tp);
> +       return timespec_to_ns(&realtime_tp);
>  }
>  
>  /**
> - * timeval_to_ns - Convert timeval to nanoseconds
> - * @ts:                pointer to the timeval variable to be 
> converted
> - *
> - * Returns the scalar nanosecond representation of the timeval
> - * parameter.
> - *
> - * Ripped from linux/time.h because it's a kernel header, and thus
> - * unusable from here.
> + * os_timer_create() - create an new posix (interval) timer
>   */
> -static inline long long timeval_to_ns(const struct timeval *tv)
> -{
> -       return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
> -               tv->tv_usec * UM_NSEC_PER_USEC;
> +int os_timer_create(void* timer) {
> +
> +       timer_t* t = timer;
> +
> +       if(t == NULL) {
> +               t = &event_high_res_timer;
> +       }
> +
> +       if (timer_create(
> +               CLOCK_MONOTONIC,
> +               NULL,
> +               t) == -1) {
> +               return -1;
> +       }
> +       return 0;
>  }
>  
> -long long disable_timer(void)
> +int os_timer_set_interval(void* timer, void* i)
>  {
> -       struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 
> 0 } });
> -       long long remain, max = UM_NSEC_PER_SEC / UM_HZ;
> +       struct itimerspec its;
> +       unsigned long long nsec;
> +       timer_t* t = timer;
> +       struct itimerspec* its_in = i;
>  
> -       if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0)
> -               printk(UM_KERN_ERR "disable_timer - setitimer failed, 
> "
> -                      "errno = %d\n", errno);
> +       if(t == NULL) {
> +               t = &event_high_res_timer;
> +       }
>  
> -       remain = timeval_to_ns(&time.it_value);
> -       if (remain > max)
> -               remain = max;
> +       nsec = UM_NSEC_PER_SEC / UM_HZ;
>  
> -       return remain;
> -}
> +       if(its_in != NULL) {
> +               its.it_value.tv_sec = its_in->it_value.tv_sec;
> +               its.it_value.tv_nsec = its_in->it_value.tv_nsec;
> +       } else {
> +               its.it_value.tv_sec = 0;
> +               its.it_value.tv_nsec = nsec;
> +       }
>  
> -long long os_nsecs(void)
> -{
> -       struct timeval tv;
> +       its.it_interval.tv_sec = 0;
> +       its.it_interval.tv_nsec = nsec;
>  
> -       gettimeofday(&tv, NULL);
> -       return timeval_to_ns(&tv);
> -}
> +       if(timer_settime(*t, 0, &its, NULL) == -1) {
> +               return -errno;
> +       }
>  
> -#ifdef UML_CONFIG_NO_HZ_COMMON
> -static int after_sleep_interval(struct timespec *ts)
> -{
>         return 0;
>  }
>  
> -static void deliver_alarm(void)
> +/**
> + * os_timer_remain() - returns the remaining nano seconds of the 
> given interval
> + *                     timer
> + * Because this is the remaining time of an interval timer, which 
> correspondends
> + * to HZ, this value can never be bigger than one second. Just
> + * the nanosecond part of the timer is returned.
> + * The returned time is relative to the start time of the interval 
> timer.
> + * Return an negative value in an error case.
> + */
> +long os_timer_remain(void* timer)
>  {
> -       alarm_handler(SIGVTALRM, NULL, NULL);
> -}
> +       struct itimerspec its;
> +       timer_t* t = timer;
>  
> -static unsigned long long sleep_time(unsigned long long nsecs)
> -{
> -       return nsecs;
> -}
> +       if(t == NULL) {
> +               t = &event_high_res_timer;
> +       }
>  
> -#else
> -unsigned long long last_tick;
> -unsigned long long skew;
> +       if(timer_gettime(t, &its) == -1) {
> +               return -errno;
> +       }
> +
> +       return its.it_value.tv_nsec;
> +}
>  
> -static void deliver_alarm(void)
> +int os_timer_one_shot(int ticks)
>  {
> -       unsigned long long this_tick = os_nsecs();
> -       int one_tick = UM_NSEC_PER_SEC / UM_HZ;
> +       struct itimerspec its;
> +       unsigned long long nsec;
> +       unsigned long sec;
>  
> -       /* Protection against the host's time going backwards */
> -       if ((last_tick != 0) && (this_tick < last_tick))
> -               this_tick = last_tick;
> +    nsec = (ticks + 1);
> +    sec = nsec / UM_NSEC_PER_SEC;
> +       nsec = nsec % UM_NSEC_PER_SEC;
>  
> -       if (last_tick == 0)
> -               last_tick = this_tick - one_tick;
> +       its.it_value.tv_sec = nsec / UM_NSEC_PER_SEC;
> +       its.it_value.tv_nsec = nsec;
>  
> -       skew += this_tick - last_tick;
> +       its.it_interval.tv_sec = 0;
> +       its.it_interval.tv_nsec = 0; // we cheat here
>  
> -       while (skew >= one_tick) {
> -               alarm_handler(SIGVTALRM, NULL, NULL);
> -               skew -= one_tick;
> -       }
> -
> -       last_tick = this_tick;
> +       timer_settime(event_high_res_timer, 0, &its, NULL);
> +       return 0;
>  }
>  
> -static unsigned long long sleep_time(unsigned long long nsecs)
> +/**
> + * os_timer_disable() - disable the posix (interval) timer
> + * Returns the remaining interval timer time in nanoseconds
> + */
> +long long os_timer_disable(void)
>  {
> -       return nsecs > skew ? nsecs - skew : 0;
> +       struct itimerspec its;
> +
> +       memset(&its, 0, sizeof(struct itimerspec));
> +       timer_settime(event_high_res_timer, 0, &its, &its);
> +
> +       return its.it_value.tv_sec * UM_NSEC_PER_SEC + 
> its.it_value.tv_nsec;
>  }
>  
> -static inline long long timespec_to_us(const struct timespec *ts)
> +long long os_vnsecs(void)
>  {
> -       return ((long long) ts->tv_sec * UM_USEC_PER_SEC) +
> -               ts->tv_nsec / UM_NSEC_PER_USEC;
> +       struct timespec ts;
> +
> +       clock_gettime(CLOCK_PROCESS_CPUTIME_ID,&ts);
> +       return timespec_to_ns(&ts);
>  }
>  
> -static int after_sleep_interval(struct timespec *ts)
> +long long os_nsecs(void)
>  {
> -       int usec = UM_USEC_PER_SEC / UM_HZ;
> -       long long start_usecs = timespec_to_us(ts);
> -       struct timeval tv;
> -       struct itimerval interval;
> -
> -       /*
> -        * It seems that rounding can increase the value returned 
> from
> -        * setitimer to larger than the one passed in.  Over time,
> -        * this will cause the remaining time to be greater than the
> -        * tick interval.  If this happens, then just reduce the 
> first
> -        * tick to the interval value.
> -        */
> -       if (start_usecs > usec)
> -               start_usecs = usec;
> -
> -       start_usecs -= skew / UM_NSEC_PER_USEC;
> -       if (start_usecs < 0)
> -               start_usecs = 0;
> -
> -       tv = ((struct timeval) { .tv_sec  = start_usecs / 
> UM_USEC_PER_SEC,
> -                                .tv_usec = start_usecs % 
> UM_USEC_PER_SEC });
> -       interval = ((struct itimerval) { { 0, usec }, tv });
> -
> -       if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
> -               return -errno;
> +       struct timespec ts;
>  
> -       return 0;
> +       clock_gettime(CLOCK_MONOTONIC,&ts);
> +       return timespec_to_ns(&ts);
>  }
> -#endif
>  
> -void idle_sleep(unsigned long long nsecs)
> +/**
> + * os_idle_sleep() - sleep for a given time of nsecs
> + * @nsecs: nanoseconds to sleep
> + */
> +void os_idle_sleep(unsigned long long nsecs)
>  {
>         struct timespec ts;
>  
> -       /*
> -        * nsecs can come in as zero, in which case, this starts a
> -        * busy loop.  To prevent this, reset nsecs to the tick
> -        * interval if it is zero.
> -        */
> -       if (nsecs == 0)
> -               nsecs = UM_NSEC_PER_SEC / UM_HZ;
> -
> -       nsecs = sleep_time(nsecs);
> -       ts = ((struct timespec) { .tv_sec       = nsecs / 
> UM_NSEC_PER_SEC,
> -                                 .tv_nsec      = nsecs % 
> UM_NSEC_PER_SEC });
> -
> -       if (nanosleep(&ts, &ts) == 0)
> -               deliver_alarm();
> -       after_sleep_interval(&ts);
> +       if (nsecs <= 0) {
> +               return;
> +       }
> +
> +       ts = ((struct timespec) {
> +                       .tv_sec  = nsecs / UM_NSEC_PER_SEC,
> +                       .tv_nsec = nsecs % UM_NSEC_PER_SEC
> +       });
> +
> +       clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, NULL);
>  }


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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Anton Ivanov]

I have it ported to 4.3-rc5 and the new timer API.

It is about half-way through a debian dist-upgrade which was reliably 
crashing earlier versions.

I am going to give it a spin over the weekend and if it is stable I will 
clean it up for submission.

A.


On 14/10/15 12:22, Thomas Meyer wrote:
> Am 14.10.2015 11:23 vorm. schrieb Anton Ivanov <anton.ivanov@kot-begemot.co.uk>:
>> On 14/10/15 09:25, Thomas Meyer wrote:
>>> Hello everyone,
>>>
>>> I would like to finish this patch, but I'm currently very busy. Sorry!
>> No worries :) I am barely keeping my head above water too :)
>>
>> Is the most up-to-date revision the one you last posted to the list?
> Yes,the post on the list was the latest version.
>
>> If
>> you have a more up-to-date one, please post it even if it does not patch
>> cleanly and needs work. I will work on it.
>>
>> A.
>>
>>> Anton: it would be great if you could finish this patch! Much appreciated!
>>>
>>> With kind regards
>>> Thomas
>>>
>>> Am 14.10.2015 8:12 vorm. schrieb Anton Ivanov <anton.ivanov@kot-begemot.co.uk>:
>>>> Thomas, I need to know if you have the time-slices for this or I should
>>>> take over and finish it.
>>>>
>>>> In addition to what Richard said I have the epoll based IRQ controller
>>>> and high-performance network pipeline which depend on it in the queue.
>>>>
>>>> Brgds,
>>>>
>>>> A.
>>>>
>>>> On 13/10/15 22:45, Richard Weinberger wrote:
>>>>> On Tue, Aug 18, 2015 at 6:04 PM, Thomas Meyer <thomas@m3y3r.de> wrote:
>>>>>> Am 15.08.2015 10:15 vorm. schrieb Richard Weinberger <richard@nod.at>:
>>>>>>> Am 09.08.2015 um 19:53 schrieb Thomas Meyer:
>>>>>>>> Switch the UML clocksource from interval timers to posix interval timers and
>>>>>>>> move to a monotonic timer.
>>>>>>>>
>>>>>>>> This fixes suspend&resume related timer issues and improves network performance
>>>>>>>> as TCP state machines are now fed with the correct time; also correct QoS and
>>>>>>>> traffic shaping.
>>>>>>> The patch is rather big. Please describe in your commit message how exactly
>>>>>>> it works and why.
>>>>>>> It changes many internals.
>>>>>> Will do so!
>>>>> Can I get an updated version of that patch?
>>>>> I really want to merge it in the next merge window.
>>>>>
>>>> ------------------------------------------------------------------------------
>>>> _______________________________________________
>>>> User-mode-linux-devel mailing list
>>>> User-mode-linux-devel@lists.sourceforge.net
>>>> https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel


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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Thomas Meyer]

Am 14.10.2015 11:23 vorm. schrieb Anton Ivanov <anton.ivanov@kot-begemot.co.uk>:
>
> On 14/10/15 09:25, Thomas Meyer wrote: 
> > Hello everyone, 
> > 
> > I would like to finish this patch, but I'm currently very busy. Sorry! 
>
> No worries :) I am barely keeping my head above water too :) 
>
> Is the most up-to-date revision the one you last posted to the list?

Yes,the post on the list was the latest version.

> If 
> you have a more up-to-date one, please post it even if it does not patch 
> cleanly and needs work. I will work on it. 
>
> A. 
>
> > 
> > Anton: it would be great if you could finish this patch! Much appreciated! 
> > 
> > With kind regards 
> > Thomas 
> > 
> > Am 14.10.2015 8:12 vorm. schrieb Anton Ivanov <anton.ivanov@kot-begemot.co.uk>: 
> >> Thomas, I need to know if you have the time-slices for this or I should 
> >> take over and finish it. 
> >> 
> >> In addition to what Richard said I have the epoll based IRQ controller 
> >> and high-performance network pipeline which depend on it in the queue. 
> >> 
> >> Brgds, 
> >> 
> >> A. 
> >> 
> >> On 13/10/15 22:45, Richard Weinberger wrote: 
> >>> On Tue, Aug 18, 2015 at 6:04 PM, Thomas Meyer <thomas@m3y3r.de> wrote: 
> >>>> Am 15.08.2015 10:15 vorm. schrieb Richard Weinberger <richard@nod.at>: 
> >>>>> Am 09.08.2015 um 19:53 schrieb Thomas Meyer: 
> >>>>>> Switch the UML clocksource from interval timers to posix interval timers and 
> >>>>>> move to a monotonic timer. 
> >>>>>> 
> >>>>>> This fixes suspend&resume related timer issues and improves network performance 
> >>>>>> as TCP state machines are now fed with the correct time; also correct QoS and 
> >>>>>> traffic shaping. 
> >>>>> The patch is rather big. Please describe in your commit message how exactly 
> >>>>> it works and why. 
> >>>>> It changes many internals. 
> >>>> Will do so! 
> >>> Can I get an updated version of that patch? 
> >>> I really want to merge it in the next merge window. 
> >>> 
> >> 
> >> ------------------------------------------------------------------------------ 
> >> _______________________________________________ 
> >> User-mode-linux-devel mailing list 
> >> User-mode-linux-devel@lists.sourceforge.net 
> >> https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel 
>
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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Anton Ivanov]

On 14/10/15 09:25, Thomas Meyer wrote:
> Hello everyone,
>
> I would like to finish this patch, but I'm currently very busy. Sorry!

No worries :) I am barely keeping my head above water too :)

Is the most up-to-date revision the one you last posted to the list? If 
you have a more up-to-date one, please post it even if it does not patch 
cleanly and needs work. I will work on it.

A.

>
> Anton: it would be great if you could finish this patch! Much appreciated!
>
> With kind regards
> Thomas
>
> Am 14.10.2015 8:12 vorm. schrieb Anton Ivanov <anton.ivanov@kot-begemot.co.uk>:
>> Thomas, I need to know if you have the time-slices for this or I should
>> take over and finish it.
>>
>> In addition to what Richard said I have the epoll based IRQ controller
>> and high-performance network pipeline which depend on it in the queue.
>>
>> Brgds,
>>
>> A.
>>
>> On 13/10/15 22:45, Richard Weinberger wrote:
>>> On Tue, Aug 18, 2015 at 6:04 PM, Thomas Meyer <thomas@m3y3r.de> wrote:
>>>> Am 15.08.2015 10:15 vorm. schrieb Richard Weinberger <richard@nod.at>:
>>>>> Am 09.08.2015 um 19:53 schrieb Thomas Meyer:
>>>>>> Switch the UML clocksource from interval timers to posix interval timers and
>>>>>> move to a monotonic timer.
>>>>>>
>>>>>> This fixes suspend&resume related timer issues and improves network performance
>>>>>> as TCP state machines are now fed with the correct time; also correct QoS and
>>>>>> traffic shaping.
>>>>> The patch is rather big. Please describe in your commit message how exactly
>>>>> it works and why.
>>>>> It changes many internals.
>>>> Will do so!
>>> Can I get an updated version of that patch?
>>> I really want to merge it in the next merge window.
>>>
>>
>> ------------------------------------------------------------------------------
>> _______________________________________________
>> User-mode-linux-devel mailing list
>> User-mode-linux-devel@lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel


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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Thomas Meyer]

Hello everyone,

I would like to finish this patch, but I'm currently very busy. Sorry!

Anton: it would be great if you could finish this patch! Much appreciated!

With kind regards
Thomas

Am 14.10.2015 8:12 vorm. schrieb Anton Ivanov <anton.ivanov@kot-begemot.co.uk>:
>
> Thomas, I need to know if you have the time-slices for this or I should 
> take over and finish it. 
>
> In addition to what Richard said I have the epoll based IRQ controller 
> and high-performance network pipeline which depend on it in the queue. 
>
> Brgds, 
>
> A. 
>
> On 13/10/15 22:45, Richard Weinberger wrote: 
> > On Tue, Aug 18, 2015 at 6:04 PM, Thomas Meyer <thomas@m3y3r.de> wrote: 
> >> Am 15.08.2015 10:15 vorm. schrieb Richard Weinberger <richard@nod.at>: 
> >>> Am 09.08.2015 um 19:53 schrieb Thomas Meyer: 
> >>>> Switch the UML clocksource from interval timers to posix interval timers and 
> >>>> move to a monotonic timer. 
> >>>> 
> >>>> This fixes suspend&resume related timer issues and improves network performance 
> >>>> as TCP state machines are now fed with the correct time; also correct QoS and 
> >>>> traffic shaping. 
> >>> The patch is rather big. Please describe in your commit message how exactly 
> >>> it works and why. 
> >>> It changes many internals. 
> >> Will do so! 
> > Can I get an updated version of that patch? 
> > I really want to merge it in the next merge window. 
> > 
>
>
> ------------------------------------------------------------------------------ 
> _______________________________________________ 
> User-mode-linux-devel mailing list 
> User-mode-linux-devel@lists.sourceforge.net 
> https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel 
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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Anton Ivanov]

Thomas, I need to know if you have the time-slices for this or I should 
take over and finish it.

In addition to what Richard said I have the epoll based IRQ controller 
and high-performance network pipeline which depend on it in the queue.

Brgds,

A.

On 13/10/15 22:45, Richard Weinberger wrote:
> On Tue, Aug 18, 2015 at 6:04 PM, Thomas Meyer <thomas@m3y3r.de> wrote:
>> Am 15.08.2015 10:15 vorm. schrieb Richard Weinberger <richard@nod.at>:
>>> Am 09.08.2015 um 19:53 schrieb Thomas Meyer:
>>>> Switch the UML clocksource from interval timers to posix interval timers and
>>>> move to a monotonic timer.
>>>>
>>>> This fixes suspend&resume related timer issues and improves network performance
>>>> as TCP state machines are now fed with the correct time; also correct QoS and
>>>> traffic shaping.
>>> The patch is rather big. Please describe in your commit message how exactly
>>> it works and why.
>>> It changes many internals.
>> Will do so!
> Can I get an updated version of that patch?
> I really want to merge it in the next merge window.
>


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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Richard Weinberger]

On Tue, Aug 18, 2015 at 6:04 PM, Thomas Meyer <thomas@m3y3r.de> wrote:
> Am 15.08.2015 10:15 vorm. schrieb Richard Weinberger <richard@nod.at>:
>>
>> Am 09.08.2015 um 19:53 schrieb Thomas Meyer:
>> > Switch the UML clocksource from interval timers to posix interval timers and
>> > move to a monotonic timer.
>> >
>> > This fixes suspend&resume related timer issues and improves network performance
>> > as TCP state machines are now fed with the correct time; also correct QoS and
>> > traffic shaping.
>>
>> The patch is rather big. Please describe in your commit message how exactly
>> it works and why.
>> It changes many internals.
>
> Will do so!

Can I get an updated version of that patch?
I really want to merge it in the next merge window.

-- 
Thanks,
//richard

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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Thomas Meyer]

Am 15.08.2015 10:15 vorm. schrieb Richard Weinberger <richard@nod.at>:
>
> Am 09.08.2015 um 19:53 schrieb Thomas Meyer: 
> > Switch the UML clocksource from interval timers to posix interval timers and 
> > move to a monotonic timer. 
> > 
> > This fixes suspend&resume related timer issues and improves network performance 
> > as TCP state machines are now fed with the correct time; also correct QoS and 
> > traffic shaping. 
>
> The patch is rather big. Please describe in your commit message how exactly 
> it works and why. 
> It changes many internals. 

Will do so!

>
> > Signed-off-by: Thomas Meyer <thomas@m3y3r.de> 
>
> Please honor also the original author of the patch. 

Sure! Give credit where credit is due!

>
> > --- 
> >  arch/um/Makefile                        |   2 +- 
> >  arch/um/include/shared/os.h             |  15 +- 
> >  arch/um/include/shared/skas/stub-data.h |   5 +- 
> >  arch/um/include/shared/timer-internal.h |  13 ++ 
> >  arch/um/kernel/process.c                |   6 +- 
> >  arch/um/kernel/skas/clone.c             |   5 - 
> >  arch/um/kernel/skas/mmu.c               |   2 + 
> >  arch/um/kernel/time.c                   |  80 +++++++---- 
> >  arch/um/os-Linux/internal.h             |   1 - 
> >  arch/um/os-Linux/main.c                 |   6 +- 
> >  arch/um/os-Linux/process.c              |   5 + 
> >  arch/um/os-Linux/signal.c               |  35 +++-- 
> >  arch/um/os-Linux/skas/process.c         |  44 ++---- 
> >  arch/um/os-Linux/time.c                 | 248 ++++++++++++++++---------------- 
> >  14 files changed, 234 insertions(+), 233 deletions(-) 
> >  create mode 100644 arch/um/include/shared/timer-internal.h 
> >  delete mode 100644 arch/um/os-Linux/internal.h 
> > 
> > diff --git a/arch/um/Makefile b/arch/um/Makefile 
> > index 098ab33..eb79b4b 100644 
> > --- a/arch/um/Makefile 
> > +++ b/arch/um/Makefile 
> > @@ -131,7 +131,7 @@ export LDS_ELF_FORMAT := $(ELF_FORMAT) 
> >  # The wrappers will select whether using "malloc" or the kernel allocator. 
> >  LINK_WRAPS = -Wl,--wrap,malloc -Wl,--wrap,free -Wl,--wrap,calloc 
> >  
> > -LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt)) 
> > +LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt)) -lrt 
> >  
> >  # Used by link-vmlinux.sh which has special support for um link 
> >  export CFLAGS_vmlinux := $(LINK-y) $(LINK_WRAPS) $(LD_FLAGS_CMDLINE) 
> > diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h 
> > index ad3fa3a..7519c98 100644 
> > --- a/arch/um/include/shared/os.h 
> > +++ b/arch/um/include/shared/os.h 
> > @@ -183,6 +183,7 @@ extern int create_mem_file(unsigned long long len); 
> >  /* process.c */ 
> >  extern unsigned long os_process_pc(int pid); 
> >  extern int os_process_parent(int pid); 
> > +extern void os_alarm_process(int pid); 
> >  extern void os_stop_process(int pid); 
> >  extern void os_kill_process(int pid, int reap_child); 
> >  extern void os_kill_ptraced_process(int pid, int reap_child); 
> > @@ -217,7 +218,7 @@ extern int set_umid(char *name); 
> >  extern char *get_umid(void); 
> >  
> >  /* signal.c */ 
> > -extern void timer_init(void); 
> > +extern void timer_set_signal_handler(void); 
> >  extern void set_sigstack(void *sig_stack, int size); 
> >  extern void remove_sigstack(void); 
> >  extern void set_handler(int sig); 
> > @@ -238,12 +239,16 @@ extern void um_early_printk(const char *s, unsigned int n); 
> >  extern void os_fix_helper_signals(void); 
> >  
> >  /* time.c */ 
> > -extern void idle_sleep(unsigned long long nsecs); 
> > -extern int set_interval(void); 
> > -extern int timer_one_shot(int ticks); 
> > -extern long long disable_timer(void); 
> > +extern void os_idle_sleep(unsigned long long nsecs); 
> > +extern int os_timer_create(void* timer); 
> > +extern int os_timer_set_interval(void* timer, void* its); 
> > +extern int os_timer_one_shot(int ticks); 
> > +extern long long os_timer_disable(void); 
> > +extern long os_timer_remain(void* timer); 
> >  extern void uml_idle_timer(void); 
> > +extern long long os_persistent_clock_emulation(void); 
> >  extern long long os_nsecs(void); 
> > +extern long long os_vnsecs(void); 
> >  
> >  /* skas/mem.c */ 
> >  extern long run_syscall_stub(struct mm_id * mm_idp, 
> > diff --git a/arch/um/include/shared/skas/stub-data.h b/arch/um/include/shared/skas/stub-data.h 
> > index f6ed92c..e09d8fd 100644 
> > --- a/arch/um/include/shared/skas/stub-data.h 
> > +++ b/arch/um/include/shared/skas/stub-data.h 
> > @@ -6,12 +6,11 @@ 
> >  #ifndef __STUB_DATA_H 
> >  #define __STUB_DATA_H 
> >  
> > -#include <sys/time.h> 
> > +#include <time.h> 
> >  
> >  struct stub_data { 
> > - long offset; 
> > + unsigned long offset; 
> >  int fd; 
> > - struct itimerval timer; 
> >  long err; 
> >  }; 
> >  
> > diff --git a/arch/um/include/shared/timer-internal.h b/arch/um/include/shared/timer-internal.h 
> > new file mode 100644 
> > index 0000000..03e6f21 
> > --- /dev/null 
> > +++ b/arch/um/include/shared/timer-internal.h 
> > @@ -0,0 +1,13 @@ 
> > +/* 
> > + * Copyright (C) 2012 - 2014 Cisco Systems 
> > + * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com) 
> > + * Licensed under the GPL 
> > + */ 
> > + 
> > +#ifndef __TIMER_INTERNAL_H__ 
> > +#define __TIMER_INTERNAL_H__ 
> > + 
> > +#define TIMER_MULTIPLIER 256 
> > +#define TIMER_MIN_DELTA  500 
> > + 
> > +#endif 
> > diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c 
> > index 68b9119..2ce38c1 100644 
> > --- a/arch/um/kernel/process.c 
> > +++ b/arch/um/kernel/process.c 
> > @@ -27,6 +27,7 @@ 
> >  #include <kern_util.h> 
> >  #include <os.h> 
> >  #include <skas.h> 
> > +#include <timer-internal.h> 
> >  
> >  /* 
> >   * This is a per-cpu array.  A processor only modifies its entry and it only 
> > @@ -201,11 +202,8 @@ void initial_thread_cb(void (*proc)(void *), void *arg) 
> >  
> >  void arch_cpu_idle(void) 
> >  { 
> > - unsigned long long nsecs; 
> > - 
> >  cpu_tasks[current_thread_info()->cpu].pid = os_getpid(); 
> > - nsecs = disable_timer(); 
> > - idle_sleep(nsecs); 
> > + os_idle_sleep(UM_NSEC_PER_SEC); 
> >  local_irq_enable(); 
> >  } 
> >  
> > diff --git a/arch/um/kernel/skas/clone.c b/arch/um/kernel/skas/clone.c 
> > index 289771d..498148b 100644 
> > --- a/arch/um/kernel/skas/clone.c 
> > +++ b/arch/um/kernel/skas/clone.c 
> > @@ -35,11 +35,6 @@ stub_clone_handler(void) 
> >  if (err) 
> >  goto out; 
> >  
> > - err = stub_syscall3(__NR_setitimer, ITIMER_VIRTUAL, 
> > -     (long) &data->timer, 0); 
> > - if (err) 
> > - goto out; 
> > - 
>
> By removing this call from our clone stub, you change the way how SKAS0 
> works. Please explain why this is needed. 

Yes, before this patch each userspace process has its own itimer, after this patch only the uml process that runs the kernel will get a timer tick. The kernel will then signal the currently active userspace task about the time event.

>
> >  remap_stack(data->fd, data->offset); 
> >  goto done; 
> >  
> > diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c 
> > index fda1deb..42e2988 100644 
> > --- a/arch/um/kernel/skas/mmu.c 
> > +++ b/arch/um/kernel/skas/mmu.c 
> > @@ -61,10 +61,12 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm) 
> >  if (current->mm != NULL && current->mm != &init_mm) 
> >  from_mm = &current->mm->context; 
> >  
> > + block_signals(); 
> >  if (from_mm) 
> >  to_mm->id.u.pid = copy_context_skas0(stack, 
> >       from_mm->id.u.pid); 
> >  else to_mm->id.u.pid = start_userspace(stack); 
> > + unblock_signals(); 
>
> Why do we have to block signals here? 

There is a small time window, when a userspace process forks itself and because of that is running in the stub code... When this process then receives a timer signal it gets confused and ends up in a loop. So a quick fix was to disable the timer interrupts when possibly entering this stub code in the userspace process.
>
> >  if (to_mm->id.u.pid < 0) { 
> >  ret = to_mm->id.u.pid; 
> > diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c 
> > index 117568d..29f1125 100644 
> > --- a/arch/um/kernel/time.c 
> > +++ b/arch/um/kernel/time.c 
> > @@ -1,4 +1,5 @@ 
> >  /* 
> > + * Copyright (C) 2012-2014 Cisco Systems 
> >   * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com) 
> >   * Licensed under the GPL 
> >   */ 
> > @@ -7,11 +8,15 @@ 
> >  #include <linux/init.h> 
> >  #include <linux/interrupt.h> 
> >  #include <linux/jiffies.h> 
> > +#include <linux/mm.h> 
> > +#include <linux/sched.h> 
> > +#include <linux/spinlock.h> 
> >  #include <linux/threads.h> 
> >  #include <asm/irq.h> 
> >  #include <asm/param.h> 
> >  #include <kern_util.h> 
> >  #include <os.h> 
> > +#include <timer-internal.h> 
> >  
> >  void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs) 
> >  { 
> > @@ -22,18 +27,20 @@ void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs) 
> >  local_irq_restore(flags); 
> >  } 
> >  
> > -static void itimer_set_mode(enum clock_event_mode mode, 
> > +static void timer_set_mode(enum clock_event_mode mode, 
> >      struct clock_event_device *evt) 
> >  { 
> >  switch (mode) { 
> >  case CLOCK_EVT_MODE_PERIODIC: 
> > - set_interval(); 
> > + os_timer_set_interval(NULL, NULL); 
> >  break; 
> >  
> > + case CLOCK_EVT_MODE_ONESHOT: 
> > + os_timer_one_shot(1); 
> > + 
> >  case CLOCK_EVT_MODE_SHUTDOWN: 
> >  case CLOCK_EVT_MODE_UNUSED: 
> > - case CLOCK_EVT_MODE_ONESHOT: 
> > - disable_timer(); 
> > + os_timer_disable(); 
> >  break; 
> >  
> >  case CLOCK_EVT_MODE_RESUME: 
> > @@ -41,68 +48,79 @@ static void itimer_set_mode(enum clock_event_mode mode, 
> >  } 
> >  } 
> >  
> > -static int itimer_next_event(unsigned long delta, 
> > +static int timer_next_event(unsigned long delta, 
> >       struct clock_event_device *evt) 
> >  { 
> > - return timer_one_shot(delta + 1); 
> > + return os_timer_one_shot(delta); 
>
> Why did you replace "delta + 1" by "delta"? 

I think this comes from Anton's original patch and AFAIU was a hack to guarantee progress with the itimer based solution.
This hack is no longer needed as the new POSIX interval timer are monotonic and do always progress correctly!

>
>
> >  } 
> >  
> > -static struct clock_event_device itimer_clockevent = { 
> > - .name = "itimer", 
> > +static struct clock_event_device timer_clockevent = { 
> > + .name = "posix-timer", 
> >  .rating = 250, 
> >  .cpumask = cpu_all_mask, 
> >  .features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT, 
> > - .set_mode = itimer_set_mode, 
> > - .set_next_event = itimer_next_event, 
> > - .shift = 32, 
> > + .set_mode = timer_set_mode, 
> > + .set_next_event = timer_next_event, 
> > + .shift = 0, 
> > + .max_delta_ns = 0xffffffff, 
> > + .min_delta_ns = TIMER_MIN_DELTA, //microsecond resolution should be enough for anyone, same as 640K RAM 
> >  .irq = 0, 
> > + .mult = 1, 
> >  }; 
> >  
> > -static irqreturn_t um_timer(int irq, void *dev) 
> > +static irqreturn_t um_timer_irq(int irq, void *dev) 
> >  { 
> > - (*itimer_clockevent.event_handler)(&itimer_clockevent); 
> > + if (get_current()->mm != NULL) 
> > + { 
> > + os_alarm_process(get_current()->mm->context.id.u.pid); 
> > + } 
> > + 
> > + (*timer_clockevent.event_handler)(&timer_clockevent); 
> >  
> >  return IRQ_HANDLED; 
> >  } 
> >  
> > -static cycle_t itimer_read(struct clocksource *cs) 
> > +static cycle_t timer_read(struct clocksource *cs) 
> >  { 
> > - return os_nsecs() / 1000; 
> > + return os_nsecs() / TIMER_MULTIPLIER; 
> >  } 
> >  
> > -static struct clocksource itimer_clocksource = { 
> > - .name = "itimer", 
> > +static struct clocksource timer_clocksource = { 
> > + .name = "timer", 
> >  .rating = 300, 
> > - .read = itimer_read, 
> > + .read = timer_read, 
> >  .mask = CLOCKSOURCE_MASK(64), 
> >  .flags = CLOCK_SOURCE_IS_CONTINUOUS, 
> >  }; 
> >  
> > -static void __init setup_itimer(void) 
> > +static void __init timer_setup(void) 
> >  { 
> >  int err; 
> >  
> > - err = request_irq(TIMER_IRQ, um_timer, 0, "timer", NULL); 
> > - if (err != 0) 
> > + err = request_irq(TIMER_IRQ, um_timer_irq, IRQF_TIMER, "hr timer", NULL); 
> > + if (err != 0) { 
> >  printk(KERN_ERR "register_timer : request_irq failed - " 
> >         "errno = %d\n", -err); 
> > + return; 
> > +    } 
> > + 
> > +    err = os_timer_create(NULL); 
> > +    if (err != 0) { 
> > +        printk(KERN_ERR "creation of timer failed - errno = %d\n", -err); 
> > +        return; 
> > +    } 
> >  
> > - itimer_clockevent.mult = div_sc(HZ, NSEC_PER_SEC, 32); 
> > - itimer_clockevent.max_delta_ns = 
> > - clockevent_delta2ns(60 * HZ, &itimer_clockevent); 
> > - itimer_clockevent.min_delta_ns = 
> > - clockevent_delta2ns(1, &itimer_clockevent); 
> > - err = clocksource_register_hz(&itimer_clocksource, USEC_PER_SEC); 
> > + err = clocksource_register_hz(&timer_clocksource, NSEC_PER_SEC/TIMER_MULTIPLIER); 
> >  if (err) { 
> >  printk(KERN_ERR "clocksource_register_hz returned %d\n", err); 
> >  return; 
> >  } 
> > - clockevents_register_device(&itimer_clockevent); 
> > + clockevents_register_device(&timer_clockevent); 
> >  } 
> >  
> >  void read_persistent_clock(struct timespec *ts) 
> >  { 
> > - long long nsecs = os_nsecs(); 
> > + long long nsecs = os_persistent_clock_emulation(); 
> >  
> >  set_normalized_timespec(ts, nsecs / NSEC_PER_SEC, 
> >  nsecs % NSEC_PER_SEC); 
> > @@ -110,6 +128,6 @@ void read_persistent_clock(struct timespec *ts) 
> >  
> >  void __init time_init(void) 
> >  { 
> > - timer_init(); 
> > - late_time_init = setup_itimer; 
> > + timer_set_signal_handler(); 
> > + late_time_init = timer_setup; 
> >  } 
> > diff --git a/arch/um/os-Linux/internal.h b/arch/um/os-Linux/internal.h 
> > deleted file mode 100644 
> > index 0dc2c9f..0000000 
> > --- a/arch/um/os-Linux/internal.h 
> > +++ /dev/null 
> > @@ -1 +0,0 @@ 
> > -void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc); 
> > diff --git a/arch/um/os-Linux/main.c b/arch/um/os-Linux/main.c 
> > index df9191a..6e36f0f 100644 
> > --- a/arch/um/os-Linux/main.c 
> > +++ b/arch/um/os-Linux/main.c 
> > @@ -163,13 +163,13 @@ int __init main(int argc, char **argv, char **envp) 
> >  
> >  /* 
> >  * This signal stuff used to be in the reboot case.  However, 
> > - * sometimes a SIGVTALRM can come in when we're halting (reproducably 
> > + * sometimes a timer signal can come in when we're halting (reproducably 
> >  * when writing out gcov information, presumably because that takes 
> >  * some time) and cause a segfault. 
> >  */ 
> >  
> > - /* stop timers and set SIGVTALRM to be ignored */ 
> > - disable_timer(); 
> > + /* stop timers and set timer signal to be ignored */ 
> > + os_timer_disable(); 
> >  
> >  /* disable SIGIO for the fds and set SIGIO to be ignored */ 
> >  err = deactivate_all_fds(); 
> > diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c 
> > index 8408aba..f3bd983 100644 
> > --- a/arch/um/os-Linux/process.c 
> > +++ b/arch/um/os-Linux/process.c 
> > @@ -89,6 +89,11 @@ int os_process_parent(int pid) 
> >  return parent; 
> >  } 
> >  
> > +void os_alarm_process(int pid) 
> > +{ 
> > + kill(pid, SIGALRM); 
> > +} 
> > + 
> >  void os_stop_process(int pid) 
> >  { 
> >  kill(pid, SIGSTOP); 
> > diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c 
> > index 036d0db..e04a4cd 100644 
> > --- a/arch/um/os-Linux/signal.c 
> > +++ b/arch/um/os-Linux/signal.c 
> > @@ -13,7 +13,6 @@ 
> >  #include <kern_util.h> 
> >  #include <os.h> 
> >  #include <sysdep/mcontext.h> 
> > -#include "internal.h" 
> >  
> >  void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = { 
> >  [SIGTRAP] = relay_signal, 
> > @@ -23,7 +22,8 @@ void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = { 
> >  [SIGBUS] = bus_handler, 
> >  [SIGSEGV] = segv_handler, 
> >  [SIGIO] = sigio_handler, 
> > - [SIGVTALRM] = timer_handler }; 
> > + [SIGALRM] = timer_handler 
> > +}; 
> >  
> >  static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc) 
> >  { 
> > @@ -38,7 +38,7 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc) 
> >  } 
> >  
> >  /* enable signals if sig isn't IRQ signal */ 
> > - if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGVTALRM)) 
> > + if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGALRM)) 
> >  unblock_signals(); 
> >  
> >  (*sig_info[sig])(sig, si, &r); 
> > @@ -55,8 +55,8 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc) 
> >  #define SIGIO_BIT 0 
> >  #define SIGIO_MASK (1 << SIGIO_BIT) 
> >  
> > -#define SIGVTALRM_BIT 1 
> > -#define SIGVTALRM_MASK (1 << SIGVTALRM_BIT) 
> > +#define SIGALRM_BIT 1 
> > +#define SIGALRM_MASK (1 << SIGALRM_BIT) 
> >  
> >  static int signals_enabled; 
> >  static unsigned int signals_pending; 
> > @@ -78,36 +78,34 @@ void sig_handler(int sig, struct siginfo *si, mcontext_t *mc) 
> >  set_signals(enabled); 
> >  } 
> >  
> > -static void real_alarm_handler(mcontext_t *mc) 
> > +static void timer_real_alarm_handler(mcontext_t *mc) 
> >  { 
> >  struct uml_pt_regs regs; 
> >  
> >  if (mc != NULL) 
> >  get_regs_from_mc(&regs, mc); 
> > - regs.is_user = 0; 
> > - unblock_signals(); 
> > - timer_handler(SIGVTALRM, NULL, &regs); 
> > + timer_handler(SIGALRM, NULL, &regs); 
> >  } 
> >  
> > -void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc) 
> > +void timer_alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc) 
> >  { 
> >  int enabled; 
> >  
> >  enabled = signals_enabled; 
> >  if (!signals_enabled) { 
> > - signals_pending |= SIGVTALRM_MASK; 
> > + signals_pending |= SIGALRM_MASK; 
> >  return; 
> >  } 
> >  
> >  block_signals(); 
> >  
> > - real_alarm_handler(mc); 
> > + timer_real_alarm_handler(mc); 
> >  set_signals(enabled); 
> >  } 
> >  
> > -void timer_init(void) 
> > +void timer_set_signal_handler(void) 
> >  { 
> > - set_handler(SIGVTALRM); 
> > + set_handler(SIGALRM); 
> >  } 
> >  
> >  void set_sigstack(void *sig_stack, int size) 
> > @@ -131,10 +129,9 @@ static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = { 
> >  
> >  [SIGIO] = sig_handler, 
> >  [SIGWINCH] = sig_handler, 
> > - [SIGVTALRM] = alarm_handler 
> > + [SIGALRM] = timer_alarm_handler 
> >  }; 
> >  
> > - 
> >  static void hard_handler(int sig, siginfo_t *si, void *p) 
> >  { 
> >  struct ucontext *uc = p; 
> > @@ -188,9 +185,9 @@ void set_handler(int sig) 
> >  
> >  /* block irq ones */ 
> >  sigemptyset(&action.sa_mask); 
> > - sigaddset(&action.sa_mask, SIGVTALRM); 
> >  sigaddset(&action.sa_mask, SIGIO); 
> >  sigaddset(&action.sa_mask, SIGWINCH); 
> > + sigaddset(&action.sa_mask, SIGALRM); 
> >  
> >  if (sig == SIGSEGV) 
> >  flags |= SA_NODEFER; 
> > @@ -283,8 +280,8 @@ void unblock_signals(void) 
> >  if (save_pending & SIGIO_MASK) 
> >  sig_handler_common(SIGIO, NULL, NULL); 
> >  
> > - if (save_pending & SIGVTALRM_MASK) 
> > - real_alarm_handler(NULL); 
> > + if (save_pending & SIGALRM_MASK) 
> > + timer_real_alarm_handler(NULL); 
> >  } 
> >  } 
> >  
> > diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c 
> > index 3dddedb..5ae4752 100644 
> > --- a/arch/um/os-Linux/skas/process.c 
> > +++ b/arch/um/os-Linux/skas/process.c 
> > @@ -45,7 +45,7 @@ static int ptrace_dump_regs(int pid) 
> >   * Signals that are OK to receive in the stub - we'll just continue it. 
> >   * SIGWINCH will happen when UML is inside a detached screen. 
> >   */ 
> > -#define STUB_SIG_MASK ((1 << SIGVTALRM) | (1 << SIGWINCH)) 
> > +#define STUB_SIG_MASK ((1 << SIGALRM) | (1 << SIGWINCH)) 
> >  
> >  /* Signals that the stub will finish with - anything else is an error */ 
> >  #define STUB_DONE_MASK (1 << SIGTRAP) 
> > @@ -179,19 +179,13 @@ extern char __syscall_stub_start[]; 
> >  static int userspace_tramp(void *stack) 
> >  { 
> >  void *addr; 
> > - int err, fd; 
> > + int fd; 
> >  unsigned long long offset; 
> >  
> >  ptrace(PTRACE_TRACEME, 0, 0, 0); 
> >  
> >  signal(SIGTERM, SIG_DFL); 
> >  signal(SIGWINCH, SIG_IGN); 
> > - err = set_interval(); 
> > - if (err) { 
> > - printk(UM_KERN_ERR "userspace_tramp - setting timer failed, " 
> > -        "errno = %d\n", err); 
> > - exit(1); 
> > - } 
> >  
> >  /* 
> >  * This has a pte, but it can't be mapped in with the usual 
> > @@ -282,7 +276,7 @@ int start_userspace(unsigned long stub_stack) 
> >         "errno = %d\n", errno); 
> >  goto out_kill; 
> >  } 
> > - } while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGVTALRM)); 
> > + } while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGALRM)); 
> >  
> >  if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) { 
> >  err = -EINVAL; 
> > @@ -315,8 +309,6 @@ int start_userspace(unsigned long stub_stack) 
> >  
> >  void userspace(struct uml_pt_regs *regs) 
> >  { 
> > - struct itimerval timer; 
> > - unsigned long long nsecs, now; 
> >  int err, status, op, pid = userspace_pid[0]; 
> >  /* To prevent races if using_sysemu changes under us.*/ 
> >  int local_using_sysemu; 
> > @@ -325,13 +317,8 @@ void userspace(struct uml_pt_regs *regs) 
> >  /* Handle any immediate reschedules or signals */ 
> >  interrupt_end(); 
> >  
> > - if (getitimer(ITIMER_VIRTUAL, &timer)) 
> > - printk(UM_KERN_ERR "Failed to get itimer, errno = %d\n", errno); 
> > - nsecs = timer.it_value.tv_sec * UM_NSEC_PER_SEC + 
> > - timer.it_value.tv_usec * UM_NSEC_PER_USEC; 
> > - nsecs += os_nsecs(); 
> > - 
> >  while (1) { 
> > + 
> >  /* 
> >  * This can legitimately fail if the process loads a 
> >  * bogus value into a segment register.  It will 
> > @@ -401,18 +388,7 @@ void userspace(struct uml_pt_regs *regs) 
> >  case SIGTRAP: 
> >  relay_signal(SIGTRAP, (struct siginfo *)&si, regs); 
> >  break; 
> > - case SIGVTALRM: 
> > - now = os_nsecs(); 
> > - if (now < nsecs) 
> > - break; 
> > - block_signals(); 
> > - (*sig_info[sig])(sig, (struct siginfo *)&si, regs); 
> > - unblock_signals(); 
> > - nsecs = timer.it_value.tv_sec * 
> > - UM_NSEC_PER_SEC + 
> > - timer.it_value.tv_usec * 
> > - UM_NSEC_PER_USEC; 
> > - nsecs += os_nsecs(); 
> > + case SIGALRM: 
> >  break; 
> >  case SIGIO: 
> >  case SIGILL: 
> > @@ -460,7 +436,6 @@ __initcall(init_thread_regs); 
> >  
> >  int copy_context_skas0(unsigned long new_stack, int pid) 
> >  { 
> > - struct timeval tv = { .tv_sec = 0, .tv_usec = UM_USEC_PER_SEC / UM_HZ }; 
> >  int err; 
> >  unsigned long current_stack = current_stub_stack(); 
> >  struct stub_data *data = (struct stub_data *) current_stack; 
> > @@ -472,11 +447,10 @@ int copy_context_skas0(unsigned long new_stack, int pid) 
> >  * prepare offset and fd of child's stack as argument for parent's 
> >  * and child's mmap2 calls 
> >  */ 
> > - *data = ((struct stub_data) { .offset = MMAP_OFFSET(new_offset), 
> > -       .fd = new_fd, 
> > -       .timer    = ((struct itimerval) 
> > -            { .it_value = tv, 
> > -      .it_interval = tv }) }); 
> > + *data = ((struct stub_data) { 
> > + .offset = MMAP_OFFSET(new_offset), 
> > + .fd     = new_fd 
> > + }); 
>
> As written above, you change the way how SKAS0 works, this needs 
> much more explaination. 

Yes, okay. See above. The userspace stub code no longer generates an itimer, so no timer information needs to be passed here.

>
> >  err = ptrace_setregs(pid, thread_regs); 
> >  if (err < 0) { 
> > diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c 
> > index e9824d5..0e2bb7d 100644 
> > --- a/arch/um/os-Linux/time.c 
> > +++ b/arch/um/os-Linux/time.c 
> > @@ -1,4 +1,5 @@ 
> >  /* 
> > + * Copyright (C) 2012-2014 Cisco Systems 
> >   * Copyright (C) 2000 - 2007 Jeff Dike (jdike{addtoit,linux.intel}.com) 
> >   * Licensed under the GPL 
> >   */ 
> > @@ -10,177 +11,172 @@ 
> >  #include <sys/time.h> 
> >  #include <kern_util.h> 
> >  #include <os.h> 
> > -#include "internal.h" 
> > +#include <string.h> 
> > +#include <timer-internal.h> 
> >  
> > -int set_interval(void) 
> > -{ 
> > - int usec = UM_USEC_PER_SEC / UM_HZ; 
> > - struct itimerval interval = ((struct itimerval) { { 0, usec }, 
> > -   { 0, usec } }); 
> > - 
> > - if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1) 
> > - return -errno; 
> > +static timer_t event_high_res_timer = 0; 
> >  
> > - return 0; 
> > +static inline long long timeval_to_ns(const struct timeval *tv) 
> > +{ 
> > + return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) + 
> > + tv->tv_usec * UM_NSEC_PER_USEC; 
> >  } 
> >  
> > -int timer_one_shot(int ticks) 
> > +static inline long long timespec_to_ns(const struct timespec *ts) 
> >  { 
> > - unsigned long usec = ticks * UM_USEC_PER_SEC / UM_HZ; 
> > - unsigned long sec = usec / UM_USEC_PER_SEC; 
> > - struct itimerval interval; 
> > - 
> > - usec %= UM_USEC_PER_SEC; 
> > - interval = ((struct itimerval) { { 0, 0 }, { sec, usec } }); 
> > + return ((long long) ts->tv_sec * UM_NSEC_PER_SEC) + 
> > + ts->tv_nsec; 
> > +} 
> >  
> > - if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1) 
> > - return -errno; 
> > +long long os_persistent_clock_emulation (void) { 
> > + struct timespec realtime_tp; 
> >  
> > - return 0; 
> > + clock_gettime(CLOCK_REALTIME, &realtime_tp); 
> > + return timespec_to_ns(&realtime_tp); 
> >  } 
> >  
> >  /** 
> > - * timeval_to_ns - Convert timeval to nanoseconds 
> > - * @ts: pointer to the timeval variable to be converted 
> > - * 
> > - * Returns the scalar nanosecond representation of the timeval 
> > - * parameter. 
> > - * 
> > - * Ripped from linux/time.h because it's a kernel header, and thus 
> > - * unusable from here. 
> > + * os_timer_create() - create an new posix (interval) timer 
> >   */ 
> > -static inline long long timeval_to_ns(const struct timeval *tv) 
> > -{ 
> > - return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) + 
> > - tv->tv_usec * UM_NSEC_PER_USEC; 
> > +int os_timer_create(void* timer) { 
> > + 
> > + timer_t* t = timer; 
> > + 
> > + if(t == NULL) { 
> > + t = &event_high_res_timer; 
> > + } 
> > + 
> > + if (timer_create( 
> > + CLOCK_MONOTONIC, 
> > + NULL, 
> > + t) == -1) { 
> > + return -1; 
> > + } 
> > + return 0; 
> >  } 
> >  
> > -long long disable_timer(void) 
> > +int os_timer_set_interval(void* timer, void* i) 
> >  { 
> > - struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } }); 
> > - long long remain, max = UM_NSEC_PER_SEC / UM_HZ; 
> > + struct itimerspec its; 
> > + unsigned long long nsec; 
> > + timer_t* t = timer; 
> > + struct itimerspec* its_in = i; 
> >  
> > - if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0) 
> > - printk(UM_KERN_ERR "disable_timer - setitimer failed, " 
> > -        "errno = %d\n", errno); 
> > + if(t == NULL) { 
> > + t = &event_high_res_timer; 
> > + } 
> >  
> > - remain = timeval_to_ns(&time.it_value); 
> > - if (remain > max) 
> > - remain = max; 
> > + nsec = UM_NSEC_PER_SEC / UM_HZ; 
> >  
> > - return remain; 
> > -} 
> > + if(its_in != NULL) { 
> > + its.it_value.tv_sec = its_in->it_value.tv_sec; 
> > + its.it_value.tv_nsec = its_in->it_value.tv_nsec; 
> > + } else { 
> > + its.it_value.tv_sec = 0; 
> > + its.it_value.tv_nsec = nsec; 
> > + } 
> >  
> > -long long os_nsecs(void) 
> > -{ 
> > - struct timeval tv; 
> > + its.it_interval.tv_sec = 0; 
> > + its.it_interval.tv_nsec = nsec; 
> >  
> > - gettimeofday(&tv, NULL); 
> > - return timeval_to_ns(&tv); 
> > -} 
> > + if(timer_settime(*t, 0, &its, NULL) == -1) { 
> > + return -errno; 
> > + } 
> >  
> > -#ifdef UML_CONFIG_NO_HZ_COMMON 
> > -static int after_sleep_interval(struct timespec *ts) 
> > -{ 
> >  return 0; 
> >  } 
> >  
> > -static void deliver_alarm(void) 
> > +/** 
> > + * os_timer_remain() - returns the remaining nano seconds of the given interval 
> > + *                     timer 
> > + * Because this is the remaining time of an interval timer, which correspondends 
> > + * to HZ, this value can never be bigger than one second. Just 
> > + * the nanosecond part of the timer is returned. 
> > + * The returned time is relative to the start time of the interval timer. 
> > + * Return an negative value in an error case. 
> > + */ 
> > +long os_timer_remain(void* timer) 
> >  { 
> > - alarm_handler(SIGVTALRM, NULL, NULL); 
> > -} 
> > + struct itimerspec its; 
> > + timer_t* t = timer; 
> >  
> > -static unsigned long long sleep_time(unsigned long long nsecs) 
> > -{ 
> > - return nsecs; 
> > -} 
> > + if(t == NULL) { 
> > + t = &event_high_res_timer; 
> > + } 
> >  
> > -#else 
> > -unsigned long long last_tick; 
> > -unsigned long long skew; 
> > + if(timer_gettime(t, &its) == -1) { 
> > + return -errno; 
> > + } 
> > + 
> > + return its.it_value.tv_nsec; 
> > +} 
> >  
> > -static void deliver_alarm(void) 
> > +int os_timer_one_shot(int ticks) 
> >  { 
> > - unsigned long long this_tick = os_nsecs(); 
> > - int one_tick = UM_NSEC_PER_SEC / UM_HZ; 
> > + struct itimerspec its; 
> > + unsigned long long nsec; 
> > + unsigned long sec; 
> >  
> > - /* Protection against the host's time going backwards */ 
> > - if ((last_tick != 0) && (this_tick < last_tick)) 
> > - this_tick = last_tick; 
> > +    nsec = (ticks + 1); 
> > +    sec = nsec / UM_NSEC_PER_SEC; 
> > + nsec = nsec % UM_NSEC_PER_SEC; 
> >  
> > - if (last_tick == 0) 
> > - last_tick = this_tick - one_tick; 
> > + its.it_value.tv_sec = nsec / UM_NSEC_PER_SEC; 
> > + its.it_value.tv_nsec = nsec; 
> >  
> > - skew += this_tick - last_tick; 
> > + its.it_interval.tv_sec = 0; 
> > + its.it_interval.tv_nsec = 0; // we cheat here 
> >  
> > - while (skew >= one_tick) { 
> > - alarm_handler(SIGVTALRM, NULL, NULL); 
> > - skew -= one_tick; 
> > - } 
> > - 
> > - last_tick = this_tick; 
> > + timer_settime(event_high_res_timer, 0, &its, NULL); 
> > + return 0; 
> >  } 
> >  
> > -static unsigned long long sleep_time(unsigned long long nsecs) 
> > +/** 
> > + * os_timer_disable() - disable the posix (interval) timer 
> > + * Returns the remaining interval timer time in nanoseconds 
> > + */ 
> > +long long os_timer_disable(void) 
> >  { 
> > - return nsecs > skew ? nsecs - skew : 0; 
> > + struct itimerspec its; 
> > + 
> > + memset(&its, 0, sizeof(struct itimerspec)); 
> > + timer_settime(event_high_res_timer, 0, &its, &its); 
> > + 
> > + return its.it_value.tv_sec * UM_NSEC_PER_SEC + its.it_value.tv_nsec; 
> >  } 
> >  
> > -static inline long long timespec_to_us(const struct timespec *ts) 
> > +long long os_vnsecs(void) 
> >  { 
> > - return ((long long) ts->tv_sec * UM_USEC_PER_SEC) + 
> > - ts->tv_nsec / UM_NSEC_PER_USEC; 
> > + struct timespec ts; 
> > + 
> > + clock_gettime(CLOCK_PROCESS_CPUTIME_ID,&ts); 
> > + return timespec_to_ns(&ts); 
> >  } 
> >  
> > -static int after_sleep_interval(struct timespec *ts) 
> > +long long os_nsecs(void) 
> >  { 
> > - int usec = UM_USEC_PER_SEC / UM_HZ; 
> > - long long start_usecs = timespec_to_us(ts); 
> > - struct timeval tv; 
> > - struct itimerval interval; 
> > - 
> > - /* 
> > - * It seems that rounding can increase the value returned from 
> > - * setitimer to larger than the one passed in.  Over time, 
> > - * this will cause the remaining time to be greater than the 
> > - * tick interval.  If this happens, then just reduce the first 
> > - * tick to the interval value. 
> > - */ 
> > - if (start_usecs > usec) 
> > - start_usecs = usec; 
> > - 
> > - start_usecs -= skew / UM_NSEC_PER_USEC; 
> > - if (start_usecs < 0) 
> > - start_usecs = 0; 
> > - 
> > - tv = ((struct timeval) { .tv_sec  = start_usecs / UM_USEC_PER_SEC, 
> > - .tv_usec = start_usecs % UM_USEC_PER_SEC }); 
> > - interval = ((struct itimerval) { { 0, usec }, tv }); 
> > - 
> > - if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1) 
> > - return -errno; 
> > + struct timespec ts; 
> >  
> > - return 0; 
> > + clock_gettime(CLOCK_MONOTONIC,&ts); 
> > + return timespec_to_ns(&ts); 
> >  } 
> > -#endif 
> >  
> > -void idle_sleep(unsigned long long nsecs) 
> > +/** 
> > + * os_idle_sleep() - sleep for a given time of nsecs 
> > + * @nsecs: nanoseconds to sleep 
> > + */ 
> > +void os_idle_sleep(unsigned long long nsecs) 
> >  { 
> >  struct timespec ts; 
> >  
> > - /* 
> > - * nsecs can come in as zero, in which case, this starts a 
> > - * busy loop.  To prevent this, reset nsecs to the tick 
> > - * interval if it is zero. 
> > - */ 
> > - if (nsecs == 0) 
> > - nsecs = UM_NSEC_PER_SEC / UM_HZ; 
> > - 
> > - nsecs = sleep_time(nsecs); 
> > - ts = ((struct timespec) { .tv_sec = nsecs / UM_NSEC_PER_SEC, 
> > -   .tv_nsec = nsecs % UM_NSEC_PER_SEC }); 
> > - 
> > - if (nanosleep(&ts, &ts) == 0) 
> > - deliver_alarm(); 
> > - after_sleep_interval(&ts); 
> > + if (nsecs <= 0) { 
> > + return; 
> > + } 
> > + 
> > + ts = ((struct timespec) { 
> > + .tv_sec  = nsecs / UM_NSEC_PER_SEC, 
> > + .tv_nsec = nsecs % UM_NSEC_PER_SEC 
> > + }); 
> > + 
> > + clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, NULL); 
> >  } 
> > 
>
> Thanks, 
> //richard 
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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Anton Ivanov]

If Thomas is busy I can pick it up ~ middle of next week and finish it.

A.

On 18/08/15 10:34, Richard Weinberger wrote:
> On Sat, Aug 15, 2015 at 6:27 PM, Anton Ivanov
> <anton.ivanov@kot-begemot.co.uk> wrote:
>> On 15/08/15 09:15, Richard Weinberger wrote:
>>> Am 09.08.2015 um 19:53 schrieb Thomas Meyer:
>>>> Switch the UML clocksource from interval timers to posix interval timers and
>>>> move to a monotonic timer.
>>>>
>>>> This fixes suspend&resume related timer issues and improves network performance
>>>> as TCP state machines are now fed with the correct time; also correct QoS and
>>>> traffic shaping.
>>> The patch is rather big. Please describe in your commit message how exactly
>>> it works and why.
>>> It changes many internals.
>> Tom, I will be happy to assist with the drafting, feel free to take the
>> draft conversation off-list until we are ready.
> BTW: I'm definitely willing to merge this patch, I you miss the merge window
> I can also merge it in -rc2 or -rc3 as it fixes some nasty issues.
>


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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Richard Weinberger]

On Sat, Aug 15, 2015 at 6:27 PM, Anton Ivanov
<anton.ivanov@kot-begemot.co.uk> wrote:
> On 15/08/15 09:15, Richard Weinberger wrote:
>> Am 09.08.2015 um 19:53 schrieb Thomas Meyer:
>>> Switch the UML clocksource from interval timers to posix interval timers and
>>> move to a monotonic timer.
>>>
>>> This fixes suspend&resume related timer issues and improves network performance
>>> as TCP state machines are now fed with the correct time; also correct QoS and
>>> traffic shaping.
>> The patch is rather big. Please describe in your commit message how exactly
>> it works and why.
>> It changes many internals.
>
> Tom, I will be happy to assist with the drafting, feel free to take the
> draft conversation off-list until we are ready.

BTW: I'm definitely willing to merge this patch, I you miss the merge window
I can also merge it in -rc2 or -rc3 as it fixes some nasty issues.

-- 
Thanks,
//richard

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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Anton Ivanov]

On 15/08/15 09:15, Richard Weinberger wrote:
> Am 09.08.2015 um 19:53 schrieb Thomas Meyer:
>> Switch the UML clocksource from interval timers to posix interval timers and
>> move to a monotonic timer.
>>
>> This fixes suspend&resume related timer issues and improves network performance
>> as TCP state machines are now fed with the correct time; also correct QoS and
>> traffic shaping.
> The patch is rather big. Please describe in your commit message how exactly
> it works and why.
> It changes many internals.

Tom, I will be happy to assist with the drafting, feel free to take the 
draft conversation off-list until we are ready.

A.

>
>> Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
> Please honor also the original author of the patch.
>
>> ---
>>   arch/um/Makefile                        |   2 +-
>>   arch/um/include/shared/os.h             |  15 +-
>>   arch/um/include/shared/skas/stub-data.h |   5 +-
>>   arch/um/include/shared/timer-internal.h |  13 ++
>>   arch/um/kernel/process.c                |   6 +-
>>   arch/um/kernel/skas/clone.c             |   5 -
>>   arch/um/kernel/skas/mmu.c               |   2 +
>>   arch/um/kernel/time.c                   |  80 +++++++----
>>   arch/um/os-Linux/internal.h             |   1 -
>>   arch/um/os-Linux/main.c                 |   6 +-
>>   arch/um/os-Linux/process.c              |   5 +
>>   arch/um/os-Linux/signal.c               |  35 +++--
>>   arch/um/os-Linux/skas/process.c         |  44 ++----
>>   arch/um/os-Linux/time.c                 | 248 ++++++++++++++++----------------
>>   14 files changed, 234 insertions(+), 233 deletions(-)
>>   create mode 100644 arch/um/include/shared/timer-internal.h
>>   delete mode 100644 arch/um/os-Linux/internal.h
>>
>> diff --git a/arch/um/Makefile b/arch/um/Makefile
>> index 098ab33..eb79b4b 100644
>> --- a/arch/um/Makefile
>> +++ b/arch/um/Makefile
>> @@ -131,7 +131,7 @@ export LDS_ELF_FORMAT := $(ELF_FORMAT)
>>   # The wrappers will select whether using "malloc" or the kernel allocator.
>>   LINK_WRAPS = -Wl,--wrap,malloc -Wl,--wrap,free -Wl,--wrap,calloc
>>   
>> -LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt))
>> +LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt)) -lrt
>>   
>>   # Used by link-vmlinux.sh which has special support for um link
>>   export CFLAGS_vmlinux := $(LINK-y) $(LINK_WRAPS) $(LD_FLAGS_CMDLINE)
>> diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
>> index ad3fa3a..7519c98 100644
>> --- a/arch/um/include/shared/os.h
>> +++ b/arch/um/include/shared/os.h
>> @@ -183,6 +183,7 @@ extern int create_mem_file(unsigned long long len);
>>   /* process.c */
>>   extern unsigned long os_process_pc(int pid);
>>   extern int os_process_parent(int pid);
>> +extern void os_alarm_process(int pid);
>>   extern void os_stop_process(int pid);
>>   extern void os_kill_process(int pid, int reap_child);
>>   extern void os_kill_ptraced_process(int pid, int reap_child);
>> @@ -217,7 +218,7 @@ extern int set_umid(char *name);
>>   extern char *get_umid(void);
>>   
>>   /* signal.c */
>> -extern void timer_init(void);
>> +extern void timer_set_signal_handler(void);
>>   extern void set_sigstack(void *sig_stack, int size);
>>   extern void remove_sigstack(void);
>>   extern void set_handler(int sig);
>> @@ -238,12 +239,16 @@ extern void um_early_printk(const char *s, unsigned int n);
>>   extern void os_fix_helper_signals(void);
>>   
>>   /* time.c */
>> -extern void idle_sleep(unsigned long long nsecs);
>> -extern int set_interval(void);
>> -extern int timer_one_shot(int ticks);
>> -extern long long disable_timer(void);
>> +extern void os_idle_sleep(unsigned long long nsecs);
>> +extern int os_timer_create(void* timer);
>> +extern int os_timer_set_interval(void* timer, void* its);
>> +extern int os_timer_one_shot(int ticks);
>> +extern long long os_timer_disable(void);
>> +extern long os_timer_remain(void* timer);
>>   extern void uml_idle_timer(void);
>> +extern long long os_persistent_clock_emulation(void);
>>   extern long long os_nsecs(void);
>> +extern long long os_vnsecs(void);
>>   
>>   /* skas/mem.c */
>>   extern long run_syscall_stub(struct mm_id * mm_idp,
>> diff --git a/arch/um/include/shared/skas/stub-data.h b/arch/um/include/shared/skas/stub-data.h
>> index f6ed92c..e09d8fd 100644
>> --- a/arch/um/include/shared/skas/stub-data.h
>> +++ b/arch/um/include/shared/skas/stub-data.h
>> @@ -6,12 +6,11 @@
>>   #ifndef __STUB_DATA_H
>>   #define __STUB_DATA_H
>>   
>> -#include <sys/time.h>
>> +#include <time.h>
>>   
>>   struct stub_data {
>> -	long offset;
>> +	unsigned long offset;
>>   	int fd;
>> -	struct itimerval timer;
>>   	long err;
>>   };
>>   
>> diff --git a/arch/um/include/shared/timer-internal.h b/arch/um/include/shared/timer-internal.h
>> new file mode 100644
>> index 0000000..03e6f21
>> --- /dev/null
>> +++ b/arch/um/include/shared/timer-internal.h
>> @@ -0,0 +1,13 @@
>> +/*
>> + * Copyright (C) 2012 - 2014 Cisco Systems
>> + * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
>> + * Licensed under the GPL
>> + */
>> +
>> +#ifndef __TIMER_INTERNAL_H__
>> +#define __TIMER_INTERNAL_H__
>> +
>> +#define TIMER_MULTIPLIER 256
>> +#define TIMER_MIN_DELTA  500
>> +
>> +#endif
>> diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
>> index 68b9119..2ce38c1 100644
>> --- a/arch/um/kernel/process.c
>> +++ b/arch/um/kernel/process.c
>> @@ -27,6 +27,7 @@
>>   #include <kern_util.h>
>>   #include <os.h>
>>   #include <skas.h>
>> +#include <timer-internal.h>
>>   
>>   /*
>>    * This is a per-cpu array.  A processor only modifies its entry and it only
>> @@ -201,11 +202,8 @@ void initial_thread_cb(void (*proc)(void *), void *arg)
>>   
>>   void arch_cpu_idle(void)
>>   {
>> -	unsigned long long nsecs;
>> -
>>   	cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
>> -	nsecs = disable_timer();
>> -	idle_sleep(nsecs);
>> +	os_idle_sleep(UM_NSEC_PER_SEC);
>>   	local_irq_enable();
>>   }
>>   
>> diff --git a/arch/um/kernel/skas/clone.c b/arch/um/kernel/skas/clone.c
>> index 289771d..498148b 100644
>> --- a/arch/um/kernel/skas/clone.c
>> +++ b/arch/um/kernel/skas/clone.c
>> @@ -35,11 +35,6 @@ stub_clone_handler(void)
>>   	if (err)
>>   		goto out;
>>   
>> -	err = stub_syscall3(__NR_setitimer, ITIMER_VIRTUAL,
>> -			    (long) &data->timer, 0);
>> -	if (err)
>> -		goto out;
>> -
> By removing this call from our clone stub, you change the way how SKAS0
> works. Please explain why this is needed.
>
>>   	remap_stack(data->fd, data->offset);
>>   	goto done;
>>   
>> diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c
>> index fda1deb..42e2988 100644
>> --- a/arch/um/kernel/skas/mmu.c
>> +++ b/arch/um/kernel/skas/mmu.c
>> @@ -61,10 +61,12 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm)
>>   	if (current->mm != NULL && current->mm != &init_mm)
>>   		from_mm = &current->mm->context;
>>   
>> +	block_signals();
>>   	if (from_mm)
>>   		to_mm->id.u.pid = copy_context_skas0(stack,
>>   						     from_mm->id.u.pid);
>>   	else to_mm->id.u.pid = start_userspace(stack);
>> +	unblock_signals();
> Why do we have to block signals here?
>
>>   	if (to_mm->id.u.pid < 0) {
>>   		ret = to_mm->id.u.pid;
>> diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c
>> index 117568d..29f1125 100644
>> --- a/arch/um/kernel/time.c
>> +++ b/arch/um/kernel/time.c
>> @@ -1,4 +1,5 @@
>>   /*
>> + * Copyright (C) 2012-2014 Cisco Systems
>>    * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
>>    * Licensed under the GPL
>>    */
>> @@ -7,11 +8,15 @@
>>   #include <linux/init.h>
>>   #include <linux/interrupt.h>
>>   #include <linux/jiffies.h>
>> +#include <linux/mm.h>
>> +#include <linux/sched.h>
>> +#include <linux/spinlock.h>
>>   #include <linux/threads.h>
>>   #include <asm/irq.h>
>>   #include <asm/param.h>
>>   #include <kern_util.h>
>>   #include <os.h>
>> +#include <timer-internal.h>
>>   
>>   void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
>>   {
>> @@ -22,18 +27,20 @@ void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
>>   	local_irq_restore(flags);
>>   }
>>   
>> -static void itimer_set_mode(enum clock_event_mode mode,
>> +static void timer_set_mode(enum clock_event_mode mode,
>>   			    struct clock_event_device *evt)
>>   {
>>   	switch (mode) {
>>   	case CLOCK_EVT_MODE_PERIODIC:
>> -		set_interval();
>> +		os_timer_set_interval(NULL, NULL);
>>   		break;
>>   
>> +	case CLOCK_EVT_MODE_ONESHOT:
>> +		os_timer_one_shot(1);
>> +
>>   	case CLOCK_EVT_MODE_SHUTDOWN:
>>   	case CLOCK_EVT_MODE_UNUSED:
>> -	case CLOCK_EVT_MODE_ONESHOT:
>> -		disable_timer();
>> +		os_timer_disable();
>>   		break;
>>   
>>   	case CLOCK_EVT_MODE_RESUME:
>> @@ -41,68 +48,79 @@ static void itimer_set_mode(enum clock_event_mode mode,
>>   	}
>>   }
>>   
>> -static int itimer_next_event(unsigned long delta,
>> +static int timer_next_event(unsigned long delta,
>>   			     struct clock_event_device *evt)
>>   {
>> -	return timer_one_shot(delta + 1);
>> +	return os_timer_one_shot(delta);
> Why did you replace "delta + 1" by "delta"?
>
>
>>   }
>>   
>> -static struct clock_event_device itimer_clockevent = {
>> -	.name		= "itimer",
>> +static struct clock_event_device timer_clockevent = {
>> +	.name		= "posix-timer",
>>   	.rating		= 250,
>>   	.cpumask	= cpu_all_mask,
>>   	.features	= CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
>> -	.set_mode	= itimer_set_mode,
>> -	.set_next_event = itimer_next_event,
>> -	.shift		= 32,
>> +	.set_mode	= timer_set_mode,
>> +	.set_next_event = timer_next_event,
>> +	.shift		= 0,
>> +	.max_delta_ns	= 0xffffffff,
>> +	.min_delta_ns	= TIMER_MIN_DELTA, //microsecond resolution should be enough for anyone, same as 640K RAM
>>   	.irq		= 0,
>> +	.mult		= 1,
>>   };
>>   
>> -static irqreturn_t um_timer(int irq, void *dev)
>> +static irqreturn_t um_timer_irq(int irq, void *dev)
>>   {
>> -	(*itimer_clockevent.event_handler)(&itimer_clockevent);
>> +	if (get_current()->mm != NULL)
>> +	{
>> +		os_alarm_process(get_current()->mm->context.id.u.pid);
>> +	}
>> +
>> +	(*timer_clockevent.event_handler)(&timer_clockevent);
>>   
>>   	return IRQ_HANDLED;
>>   }
>>   
>> -static cycle_t itimer_read(struct clocksource *cs)
>> +static cycle_t timer_read(struct clocksource *cs)
>>   {
>> -	return os_nsecs() / 1000;
>> +	return os_nsecs() / TIMER_MULTIPLIER;
>>   }
>>   
>> -static struct clocksource itimer_clocksource = {
>> -	.name		= "itimer",
>> +static struct clocksource timer_clocksource = {
>> +	.name		= "timer",
>>   	.rating		= 300,
>> -	.read		= itimer_read,
>> +	.read		= timer_read,
>>   	.mask		= CLOCKSOURCE_MASK(64),
>>   	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
>>   };
>>   
>> -static void __init setup_itimer(void)
>> +static void __init timer_setup(void)
>>   {
>>   	int err;
>>   
>> -	err = request_irq(TIMER_IRQ, um_timer, 0, "timer", NULL);
>> -	if (err != 0)
>> +	err = request_irq(TIMER_IRQ, um_timer_irq, IRQF_TIMER, "hr timer", NULL);
>> +	if (err != 0) {
>>   		printk(KERN_ERR "register_timer : request_irq failed - "
>>   		       "errno = %d\n", -err);
>> +		return;
>> +    }
>> +
>> +    err = os_timer_create(NULL);
>> +    if (err != 0) {
>> +        printk(KERN_ERR "creation of timer failed - errno = %d\n", -err);
>> +        return;
>> +    }
>>   
>> -	itimer_clockevent.mult = div_sc(HZ, NSEC_PER_SEC, 32);
>> -	itimer_clockevent.max_delta_ns =
>> -		clockevent_delta2ns(60 * HZ, &itimer_clockevent);
>> -	itimer_clockevent.min_delta_ns =
>> -		clockevent_delta2ns(1, &itimer_clockevent);
>> -	err = clocksource_register_hz(&itimer_clocksource, USEC_PER_SEC);
>> +	err = clocksource_register_hz(&timer_clocksource, NSEC_PER_SEC/TIMER_MULTIPLIER);
>>   	if (err) {
>>   		printk(KERN_ERR "clocksource_register_hz returned %d\n", err);
>>   		return;
>>   	}
>> -	clockevents_register_device(&itimer_clockevent);
>> +	clockevents_register_device(&timer_clockevent);
>>   }
>>   
>>   void read_persistent_clock(struct timespec *ts)
>>   {
>> -	long long nsecs = os_nsecs();
>> +	long long nsecs = os_persistent_clock_emulation();
>>   
>>   	set_normalized_timespec(ts, nsecs / NSEC_PER_SEC,
>>   				nsecs % NSEC_PER_SEC);
>> @@ -110,6 +128,6 @@ void read_persistent_clock(struct timespec *ts)
>>   
>>   void __init time_init(void)
>>   {
>> -	timer_init();
>> -	late_time_init = setup_itimer;
>> +	timer_set_signal_handler();
>> +	late_time_init = timer_setup;
>>   }
>> diff --git a/arch/um/os-Linux/internal.h b/arch/um/os-Linux/internal.h
>> deleted file mode 100644
>> index 0dc2c9f..0000000
>> --- a/arch/um/os-Linux/internal.h
>> +++ /dev/null
>> @@ -1 +0,0 @@
>> -void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc);
>> diff --git a/arch/um/os-Linux/main.c b/arch/um/os-Linux/main.c
>> index df9191a..6e36f0f 100644
>> --- a/arch/um/os-Linux/main.c
>> +++ b/arch/um/os-Linux/main.c
>> @@ -163,13 +163,13 @@ int __init main(int argc, char **argv, char **envp)
>>   
>>   	/*
>>   	 * This signal stuff used to be in the reboot case.  However,
>> -	 * sometimes a SIGVTALRM can come in when we're halting (reproducably
>> +	 * sometimes a timer signal can come in when we're halting (reproducably
>>   	 * when writing out gcov information, presumably because that takes
>>   	 * some time) and cause a segfault.
>>   	 */
>>   
>> -	/* stop timers and set SIGVTALRM to be ignored */
>> -	disable_timer();
>> +	/* stop timers and set timer signal to be ignored */
>> +	os_timer_disable();
>>   
>>   	/* disable SIGIO for the fds and set SIGIO to be ignored */
>>   	err = deactivate_all_fds();
>> diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c
>> index 8408aba..f3bd983 100644
>> --- a/arch/um/os-Linux/process.c
>> +++ b/arch/um/os-Linux/process.c
>> @@ -89,6 +89,11 @@ int os_process_parent(int pid)
>>   	return parent;
>>   }
>>   
>> +void os_alarm_process(int pid)
>> +{
>> +	kill(pid, SIGALRM);
>> +}
>> +
>>   void os_stop_process(int pid)
>>   {
>>   	kill(pid, SIGSTOP);
>> diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
>> index 036d0db..e04a4cd 100644
>> --- a/arch/um/os-Linux/signal.c
>> +++ b/arch/um/os-Linux/signal.c
>> @@ -13,7 +13,6 @@
>>   #include <kern_util.h>
>>   #include <os.h>
>>   #include <sysdep/mcontext.h>
>> -#include "internal.h"
>>   
>>   void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
>>   	[SIGTRAP]	= relay_signal,
>> @@ -23,7 +22,8 @@ void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
>>   	[SIGBUS]	= bus_handler,
>>   	[SIGSEGV]	= segv_handler,
>>   	[SIGIO]		= sigio_handler,
>> -	[SIGVTALRM]	= timer_handler };
>> +	[SIGALRM]	= timer_handler
>> +};
>>   
>>   static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
>>   {
>> @@ -38,7 +38,7 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
>>   	}
>>   
>>   	/* enable signals if sig isn't IRQ signal */
>> -	if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGVTALRM))
>> +	if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGALRM))
>>   		unblock_signals();
>>   
>>   	(*sig_info[sig])(sig, si, &r);
>> @@ -55,8 +55,8 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
>>   #define SIGIO_BIT 0
>>   #define SIGIO_MASK (1 << SIGIO_BIT)
>>   
>> -#define SIGVTALRM_BIT 1
>> -#define SIGVTALRM_MASK (1 << SIGVTALRM_BIT)
>> +#define SIGALRM_BIT 1
>> +#define SIGALRM_MASK (1 << SIGALRM_BIT)
>>   
>>   static int signals_enabled;
>>   static unsigned int signals_pending;
>> @@ -78,36 +78,34 @@ void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
>>   	set_signals(enabled);
>>   }
>>   
>> -static void real_alarm_handler(mcontext_t *mc)
>> +static void timer_real_alarm_handler(mcontext_t *mc)
>>   {
>>   	struct uml_pt_regs regs;
>>   
>>   	if (mc != NULL)
>>   		get_regs_from_mc(&regs, mc);
>> -	regs.is_user = 0;
>> -	unblock_signals();
>> -	timer_handler(SIGVTALRM, NULL, &regs);
>> +	timer_handler(SIGALRM, NULL, &regs);
>>   }
>>   
>> -void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
>> +void timer_alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
>>   {
>>   	int enabled;
>>   
>>   	enabled = signals_enabled;
>>   	if (!signals_enabled) {
>> -		signals_pending |= SIGVTALRM_MASK;
>> +		signals_pending |= SIGALRM_MASK;
>>   		return;
>>   	}
>>   
>>   	block_signals();
>>   
>> -	real_alarm_handler(mc);
>> +	timer_real_alarm_handler(mc);
>>   	set_signals(enabled);
>>   }
>>   
>> -void timer_init(void)
>> +void timer_set_signal_handler(void)
>>   {
>> -	set_handler(SIGVTALRM);
>> +	set_handler(SIGALRM);
>>   }
>>   
>>   void set_sigstack(void *sig_stack, int size)
>> @@ -131,10 +129,9 @@ static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
>>   
>>   	[SIGIO] = sig_handler,
>>   	[SIGWINCH] = sig_handler,
>> -	[SIGVTALRM] = alarm_handler
>> +	[SIGALRM] = timer_alarm_handler
>>   };
>>   
>> -
>>   static void hard_handler(int sig, siginfo_t *si, void *p)
>>   {
>>   	struct ucontext *uc = p;
>> @@ -188,9 +185,9 @@ void set_handler(int sig)
>>   
>>   	/* block irq ones */
>>   	sigemptyset(&action.sa_mask);
>> -	sigaddset(&action.sa_mask, SIGVTALRM);
>>   	sigaddset(&action.sa_mask, SIGIO);
>>   	sigaddset(&action.sa_mask, SIGWINCH);
>> +	sigaddset(&action.sa_mask, SIGALRM);
>>   
>>   	if (sig == SIGSEGV)
>>   		flags |= SA_NODEFER;
>> @@ -283,8 +280,8 @@ void unblock_signals(void)
>>   		if (save_pending & SIGIO_MASK)
>>   			sig_handler_common(SIGIO, NULL, NULL);
>>   
>> -		if (save_pending & SIGVTALRM_MASK)
>> -			real_alarm_handler(NULL);
>> +		if (save_pending & SIGALRM_MASK)
>> +			timer_real_alarm_handler(NULL);
>>   	}
>>   }
>>   
>> diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
>> index 3dddedb..5ae4752 100644
>> --- a/arch/um/os-Linux/skas/process.c
>> +++ b/arch/um/os-Linux/skas/process.c
>> @@ -45,7 +45,7 @@ static int ptrace_dump_regs(int pid)
>>    * Signals that are OK to receive in the stub - we'll just continue it.
>>    * SIGWINCH will happen when UML is inside a detached screen.
>>    */
>> -#define STUB_SIG_MASK ((1 << SIGVTALRM) | (1 << SIGWINCH))
>> +#define STUB_SIG_MASK ((1 << SIGALRM) | (1 << SIGWINCH))
>>   
>>   /* Signals that the stub will finish with - anything else is an error */
>>   #define STUB_DONE_MASK (1 << SIGTRAP)
>> @@ -179,19 +179,13 @@ extern char __syscall_stub_start[];
>>   static int userspace_tramp(void *stack)
>>   {
>>   	void *addr;
>> -	int err, fd;
>> +	int fd;
>>   	unsigned long long offset;
>>   
>>   	ptrace(PTRACE_TRACEME, 0, 0, 0);
>>   
>>   	signal(SIGTERM, SIG_DFL);
>>   	signal(SIGWINCH, SIG_IGN);
>> -	err = set_interval();
>> -	if (err) {
>> -		printk(UM_KERN_ERR "userspace_tramp - setting timer failed, "
>> -		       "errno = %d\n", err);
>> -		exit(1);
>> -	}
>>   
>>   	/*
>>   	 * This has a pte, but it can't be mapped in with the usual
>> @@ -282,7 +276,7 @@ int start_userspace(unsigned long stub_stack)
>>   			       "errno = %d\n", errno);
>>   			goto out_kill;
>>   		}
>> -	} while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGVTALRM));
>> +	} while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGALRM));
>>   
>>   	if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
>>   		err = -EINVAL;
>> @@ -315,8 +309,6 @@ int start_userspace(unsigned long stub_stack)
>>   
>>   void userspace(struct uml_pt_regs *regs)
>>   {
>> -	struct itimerval timer;
>> -	unsigned long long nsecs, now;
>>   	int err, status, op, pid = userspace_pid[0];
>>   	/* To prevent races if using_sysemu changes under us.*/
>>   	int local_using_sysemu;
>> @@ -325,13 +317,8 @@ void userspace(struct uml_pt_regs *regs)
>>   	/* Handle any immediate reschedules or signals */
>>   	interrupt_end();
>>   
>> -	if (getitimer(ITIMER_VIRTUAL, &timer))
>> -		printk(UM_KERN_ERR "Failed to get itimer, errno = %d\n", errno);
>> -	nsecs = timer.it_value.tv_sec * UM_NSEC_PER_SEC +
>> -		timer.it_value.tv_usec * UM_NSEC_PER_USEC;
>> -	nsecs += os_nsecs();
>> -
>>   	while (1) {
>> +
>>   		/*
>>   		 * This can legitimately fail if the process loads a
>>   		 * bogus value into a segment register.  It will
>> @@ -401,18 +388,7 @@ void userspace(struct uml_pt_regs *regs)
>>   			case SIGTRAP:
>>   				relay_signal(SIGTRAP, (struct siginfo *)&si, regs);
>>   				break;
>> -			case SIGVTALRM:
>> -				now = os_nsecs();
>> -				if (now < nsecs)
>> -					break;
>> -				block_signals();
>> -				(*sig_info[sig])(sig, (struct siginfo *)&si, regs);
>> -				unblock_signals();
>> -				nsecs = timer.it_value.tv_sec *
>> -					UM_NSEC_PER_SEC +
>> -					timer.it_value.tv_usec *
>> -					UM_NSEC_PER_USEC;
>> -				nsecs += os_nsecs();
>> +			case SIGALRM:
>>   				break;
>>   			case SIGIO:
>>   			case SIGILL:
>> @@ -460,7 +436,6 @@ __initcall(init_thread_regs);
>>   
>>   int copy_context_skas0(unsigned long new_stack, int pid)
>>   {
>> -	struct timeval tv = { .tv_sec = 0, .tv_usec = UM_USEC_PER_SEC / UM_HZ };
>>   	int err;
>>   	unsigned long current_stack = current_stub_stack();
>>   	struct stub_data *data = (struct stub_data *) current_stack;
>> @@ -472,11 +447,10 @@ int copy_context_skas0(unsigned long new_stack, int pid)
>>   	 * prepare offset and fd of child's stack as argument for parent's
>>   	 * and child's mmap2 calls
>>   	 */
>> -	*data = ((struct stub_data) { .offset	= MMAP_OFFSET(new_offset),
>> -				      .fd	= new_fd,
>> -				      .timer    = ((struct itimerval)
>> -					           { .it_value = tv,
>> -						     .it_interval = tv }) });
>> +	*data = ((struct stub_data) {
>> +			.offset	= MMAP_OFFSET(new_offset),
>> +			.fd     = new_fd
>> +	});
> As written above, you change the way how SKAS0 works, this needs
> much more explaination.
>
>>   	err = ptrace_setregs(pid, thread_regs);
>>   	if (err < 0) {
>> diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c
>> index e9824d5..0e2bb7d 100644
>> --- a/arch/um/os-Linux/time.c
>> +++ b/arch/um/os-Linux/time.c
>> @@ -1,4 +1,5 @@
>>   /*
>> + * Copyright (C) 2012-2014 Cisco Systems
>>    * Copyright (C) 2000 - 2007 Jeff Dike (jdike{addtoit,linux.intel}.com)
>>    * Licensed under the GPL
>>    */
>> @@ -10,177 +11,172 @@
>>   #include <sys/time.h>
>>   #include <kern_util.h>
>>   #include <os.h>
>> -#include "internal.h"
>> +#include <string.h>
>> +#include <timer-internal.h>
>>   
>> -int set_interval(void)
>> -{
>> -	int usec = UM_USEC_PER_SEC / UM_HZ;
>> -	struct itimerval interval = ((struct itimerval) { { 0, usec },
>> -							  { 0, usec } });
>> -
>> -	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
>> -		return -errno;
>> +static timer_t event_high_res_timer = 0;
>>   
>> -	return 0;
>> +static inline long long timeval_to_ns(const struct timeval *tv)
>> +{
>> +	return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
>> +		tv->tv_usec * UM_NSEC_PER_USEC;
>>   }
>>   
>> -int timer_one_shot(int ticks)
>> +static inline long long timespec_to_ns(const struct timespec *ts)
>>   {
>> -	unsigned long usec = ticks * UM_USEC_PER_SEC / UM_HZ;
>> -	unsigned long sec = usec / UM_USEC_PER_SEC;
>> -	struct itimerval interval;
>> -
>> -	usec %= UM_USEC_PER_SEC;
>> -	interval = ((struct itimerval) { { 0, 0 }, { sec, usec } });
>> +	return ((long long) ts->tv_sec * UM_NSEC_PER_SEC) +
>> +		ts->tv_nsec;
>> +}
>>   
>> -	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
>> -		return -errno;
>> +long long os_persistent_clock_emulation (void) {
>> +	struct timespec realtime_tp;
>>   
>> -	return 0;
>> +	clock_gettime(CLOCK_REALTIME, &realtime_tp);
>> +	return timespec_to_ns(&realtime_tp);
>>   }
>>   
>>   /**
>> - * timeval_to_ns - Convert timeval to nanoseconds
>> - * @ts:		pointer to the timeval variable to be converted
>> - *
>> - * Returns the scalar nanosecond representation of the timeval
>> - * parameter.
>> - *
>> - * Ripped from linux/time.h because it's a kernel header, and thus
>> - * unusable from here.
>> + * os_timer_create() - create an new posix (interval) timer
>>    */
>> -static inline long long timeval_to_ns(const struct timeval *tv)
>> -{
>> -	return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
>> -		tv->tv_usec * UM_NSEC_PER_USEC;
>> +int os_timer_create(void* timer) {
>> +
>> +	timer_t* t = timer;
>> +
>> +	if(t == NULL) {
>> +		t = &event_high_res_timer;
>> +	}
>> +
>> +	if (timer_create(
>> +		CLOCK_MONOTONIC,
>> +		NULL,
>> +		t) == -1) {
>> +		return -1;
>> +	}
>> +	return 0;
>>   }
>>   
>> -long long disable_timer(void)
>> +int os_timer_set_interval(void* timer, void* i)
>>   {
>> -	struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } });
>> -	long long remain, max = UM_NSEC_PER_SEC / UM_HZ;
>> +	struct itimerspec its;
>> +	unsigned long long nsec;
>> +	timer_t* t = timer;
>> +	struct itimerspec* its_in = i;
>>   
>> -	if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0)
>> -		printk(UM_KERN_ERR "disable_timer - setitimer failed, "
>> -		       "errno = %d\n", errno);
>> +	if(t == NULL) {
>> +		t = &event_high_res_timer;
>> +	}
>>   
>> -	remain = timeval_to_ns(&time.it_value);
>> -	if (remain > max)
>> -		remain = max;
>> +	nsec = UM_NSEC_PER_SEC / UM_HZ;
>>   
>> -	return remain;
>> -}
>> +	if(its_in != NULL) {
>> +		its.it_value.tv_sec = its_in->it_value.tv_sec;
>> +		its.it_value.tv_nsec = its_in->it_value.tv_nsec;
>> +	} else {
>> +		its.it_value.tv_sec = 0;
>> +		its.it_value.tv_nsec = nsec;
>> +	}
>>   
>> -long long os_nsecs(void)
>> -{
>> -	struct timeval tv;
>> +	its.it_interval.tv_sec = 0;
>> +	its.it_interval.tv_nsec = nsec;
>>   
>> -	gettimeofday(&tv, NULL);
>> -	return timeval_to_ns(&tv);
>> -}
>> +	if(timer_settime(*t, 0, &its, NULL) == -1) {
>> +		return -errno;
>> +	}
>>   
>> -#ifdef UML_CONFIG_NO_HZ_COMMON
>> -static int after_sleep_interval(struct timespec *ts)
>> -{
>>   	return 0;
>>   }
>>   
>> -static void deliver_alarm(void)
>> +/**
>> + * os_timer_remain() - returns the remaining nano seconds of the given interval
>> + *                     timer
>> + * Because this is the remaining time of an interval timer, which correspondends
>> + * to HZ, this value can never be bigger than one second. Just
>> + * the nanosecond part of the timer is returned.
>> + * The returned time is relative to the start time of the interval timer.
>> + * Return an negative value in an error case.
>> + */
>> +long os_timer_remain(void* timer)
>>   {
>> -	alarm_handler(SIGVTALRM, NULL, NULL);
>> -}
>> +	struct itimerspec its;
>> +	timer_t* t = timer;
>>   
>> -static unsigned long long sleep_time(unsigned long long nsecs)
>> -{
>> -	return nsecs;
>> -}
>> +	if(t == NULL) {
>> +		t = &event_high_res_timer;
>> +	}
>>   
>> -#else
>> -unsigned long long last_tick;
>> -unsigned long long skew;
>> +	if(timer_gettime(t, &its) == -1) {
>> +		return -errno;
>> +	}
>> +
>> +	return its.it_value.tv_nsec;
>> +}
>>   
>> -static void deliver_alarm(void)
>> +int os_timer_one_shot(int ticks)
>>   {
>> -	unsigned long long this_tick = os_nsecs();
>> -	int one_tick = UM_NSEC_PER_SEC / UM_HZ;
>> +	struct itimerspec its;
>> +	unsigned long long nsec;
>> +	unsigned long sec;
>>   
>> -	/* Protection against the host's time going backwards */
>> -	if ((last_tick != 0) && (this_tick < last_tick))
>> -		this_tick = last_tick;
>> +    nsec = (ticks + 1);
>> +    sec = nsec / UM_NSEC_PER_SEC;
>> +	nsec = nsec % UM_NSEC_PER_SEC;
>>   
>> -	if (last_tick == 0)
>> -		last_tick = this_tick - one_tick;
>> +	its.it_value.tv_sec = nsec / UM_NSEC_PER_SEC;
>> +	its.it_value.tv_nsec = nsec;
>>   
>> -	skew += this_tick - last_tick;
>> +	its.it_interval.tv_sec = 0;
>> +	its.it_interval.tv_nsec = 0; // we cheat here
>>   
>> -	while (skew >= one_tick) {
>> -		alarm_handler(SIGVTALRM, NULL, NULL);
>> -		skew -= one_tick;
>> -	}
>> -
>> -	last_tick = this_tick;
>> +	timer_settime(event_high_res_timer, 0, &its, NULL);
>> +	return 0;
>>   }
>>   
>> -static unsigned long long sleep_time(unsigned long long nsecs)
>> +/**
>> + * os_timer_disable() - disable the posix (interval) timer
>> + * Returns the remaining interval timer time in nanoseconds
>> + */
>> +long long os_timer_disable(void)
>>   {
>> -	return nsecs > skew ? nsecs - skew : 0;
>> +	struct itimerspec its;
>> +
>> +	memset(&its, 0, sizeof(struct itimerspec));
>> +	timer_settime(event_high_res_timer, 0, &its, &its);
>> +
>> +	return its.it_value.tv_sec * UM_NSEC_PER_SEC + its.it_value.tv_nsec;
>>   }
>>   
>> -static inline long long timespec_to_us(const struct timespec *ts)
>> +long long os_vnsecs(void)
>>   {
>> -	return ((long long) ts->tv_sec * UM_USEC_PER_SEC) +
>> -		ts->tv_nsec / UM_NSEC_PER_USEC;
>> +	struct timespec ts;
>> +
>> +	clock_gettime(CLOCK_PROCESS_CPUTIME_ID,&ts);
>> +	return timespec_to_ns(&ts);
>>   }
>>   
>> -static int after_sleep_interval(struct timespec *ts)
>> +long long os_nsecs(void)
>>   {
>> -	int usec = UM_USEC_PER_SEC / UM_HZ;
>> -	long long start_usecs = timespec_to_us(ts);
>> -	struct timeval tv;
>> -	struct itimerval interval;
>> -
>> -	/*
>> -	 * It seems that rounding can increase the value returned from
>> -	 * setitimer to larger than the one passed in.  Over time,
>> -	 * this will cause the remaining time to be greater than the
>> -	 * tick interval.  If this happens, then just reduce the first
>> -	 * tick to the interval value.
>> -	 */
>> -	if (start_usecs > usec)
>> -		start_usecs = usec;
>> -
>> -	start_usecs -= skew / UM_NSEC_PER_USEC;
>> -	if (start_usecs < 0)
>> -		start_usecs = 0;
>> -
>> -	tv = ((struct timeval) { .tv_sec  = start_usecs / UM_USEC_PER_SEC,
>> -				 .tv_usec = start_usecs % UM_USEC_PER_SEC });
>> -	interval = ((struct itimerval) { { 0, usec }, tv });
>> -
>> -	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
>> -		return -errno;
>> +	struct timespec ts;
>>   
>> -	return 0;
>> +	clock_gettime(CLOCK_MONOTONIC,&ts);
>> +	return timespec_to_ns(&ts);
>>   }
>> -#endif
>>   
>> -void idle_sleep(unsigned long long nsecs)
>> +/**
>> + * os_idle_sleep() - sleep for a given time of nsecs
>> + * @nsecs: nanoseconds to sleep
>> + */
>> +void os_idle_sleep(unsigned long long nsecs)
>>   {
>>   	struct timespec ts;
>>   
>> -	/*
>> -	 * nsecs can come in as zero, in which case, this starts a
>> -	 * busy loop.  To prevent this, reset nsecs to the tick
>> -	 * interval if it is zero.
>> -	 */
>> -	if (nsecs == 0)
>> -		nsecs = UM_NSEC_PER_SEC / UM_HZ;
>> -
>> -	nsecs = sleep_time(nsecs);
>> -	ts = ((struct timespec) { .tv_sec	= nsecs / UM_NSEC_PER_SEC,
>> -				  .tv_nsec	= nsecs % UM_NSEC_PER_SEC });
>> -
>> -	if (nanosleep(&ts, &ts) == 0)
>> -		deliver_alarm();
>> -	after_sleep_interval(&ts);
>> +	if (nsecs <= 0) {
>> +		return;
>> +	}
>> +
>> +	ts = ((struct timespec) {
>> +			.tv_sec  = nsecs / UM_NSEC_PER_SEC,
>> +			.tv_nsec = nsecs % UM_NSEC_PER_SEC
>> +	});
>> +
>> +	clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, NULL);
>>   }
>>
> Thanks,
> //richard
>
> ------------------------------------------------------------------------------
> _______________________________________________
> User-mode-linux-devel mailing list
> User-mode-linux-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
>


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Re: [uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Richard Weinberger]

Am 09.08.2015 um 19:53 schrieb Thomas Meyer:
> Switch the UML clocksource from interval timers to posix interval timers and
> move to a monotonic timer.
> 
> This fixes suspend&resume related timer issues and improves network performance
> as TCP state machines are now fed with the correct time; also correct QoS and
> traffic shaping.

The patch is rather big. Please describe in your commit message how exactly
it works and why.
It changes many internals.

> Signed-off-by: Thomas Meyer <thomas@m3y3r.de>

Please honor also the original author of the patch.

> ---
>  arch/um/Makefile                        |   2 +-
>  arch/um/include/shared/os.h             |  15 +-
>  arch/um/include/shared/skas/stub-data.h |   5 +-
>  arch/um/include/shared/timer-internal.h |  13 ++
>  arch/um/kernel/process.c                |   6 +-
>  arch/um/kernel/skas/clone.c             |   5 -
>  arch/um/kernel/skas/mmu.c               |   2 +
>  arch/um/kernel/time.c                   |  80 +++++++----
>  arch/um/os-Linux/internal.h             |   1 -
>  arch/um/os-Linux/main.c                 |   6 +-
>  arch/um/os-Linux/process.c              |   5 +
>  arch/um/os-Linux/signal.c               |  35 +++--
>  arch/um/os-Linux/skas/process.c         |  44 ++----
>  arch/um/os-Linux/time.c                 | 248 ++++++++++++++++----------------
>  14 files changed, 234 insertions(+), 233 deletions(-)
>  create mode 100644 arch/um/include/shared/timer-internal.h
>  delete mode 100644 arch/um/os-Linux/internal.h
> 
> diff --git a/arch/um/Makefile b/arch/um/Makefile
> index 098ab33..eb79b4b 100644
> --- a/arch/um/Makefile
> +++ b/arch/um/Makefile
> @@ -131,7 +131,7 @@ export LDS_ELF_FORMAT := $(ELF_FORMAT)
>  # The wrappers will select whether using "malloc" or the kernel allocator.
>  LINK_WRAPS = -Wl,--wrap,malloc -Wl,--wrap,free -Wl,--wrap,calloc
>  
> -LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt))
> +LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt)) -lrt
>  
>  # Used by link-vmlinux.sh which has special support for um link
>  export CFLAGS_vmlinux := $(LINK-y) $(LINK_WRAPS) $(LD_FLAGS_CMDLINE)
> diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
> index ad3fa3a..7519c98 100644
> --- a/arch/um/include/shared/os.h
> +++ b/arch/um/include/shared/os.h
> @@ -183,6 +183,7 @@ extern int create_mem_file(unsigned long long len);
>  /* process.c */
>  extern unsigned long os_process_pc(int pid);
>  extern int os_process_parent(int pid);
> +extern void os_alarm_process(int pid);
>  extern void os_stop_process(int pid);
>  extern void os_kill_process(int pid, int reap_child);
>  extern void os_kill_ptraced_process(int pid, int reap_child);
> @@ -217,7 +218,7 @@ extern int set_umid(char *name);
>  extern char *get_umid(void);
>  
>  /* signal.c */
> -extern void timer_init(void);
> +extern void timer_set_signal_handler(void);
>  extern void set_sigstack(void *sig_stack, int size);
>  extern void remove_sigstack(void);
>  extern void set_handler(int sig);
> @@ -238,12 +239,16 @@ extern void um_early_printk(const char *s, unsigned int n);
>  extern void os_fix_helper_signals(void);
>  
>  /* time.c */
> -extern void idle_sleep(unsigned long long nsecs);
> -extern int set_interval(void);
> -extern int timer_one_shot(int ticks);
> -extern long long disable_timer(void);
> +extern void os_idle_sleep(unsigned long long nsecs);
> +extern int os_timer_create(void* timer);
> +extern int os_timer_set_interval(void* timer, void* its);
> +extern int os_timer_one_shot(int ticks);
> +extern long long os_timer_disable(void);
> +extern long os_timer_remain(void* timer);
>  extern void uml_idle_timer(void);
> +extern long long os_persistent_clock_emulation(void);
>  extern long long os_nsecs(void);
> +extern long long os_vnsecs(void);
>  
>  /* skas/mem.c */
>  extern long run_syscall_stub(struct mm_id * mm_idp,
> diff --git a/arch/um/include/shared/skas/stub-data.h b/arch/um/include/shared/skas/stub-data.h
> index f6ed92c..e09d8fd 100644
> --- a/arch/um/include/shared/skas/stub-data.h
> +++ b/arch/um/include/shared/skas/stub-data.h
> @@ -6,12 +6,11 @@
>  #ifndef __STUB_DATA_H
>  #define __STUB_DATA_H
>  
> -#include <sys/time.h>
> +#include <time.h>
>  
>  struct stub_data {
> -	long offset;
> +	unsigned long offset;
>  	int fd;
> -	struct itimerval timer;
>  	long err;
>  };
>  
> diff --git a/arch/um/include/shared/timer-internal.h b/arch/um/include/shared/timer-internal.h
> new file mode 100644
> index 0000000..03e6f21
> --- /dev/null
> +++ b/arch/um/include/shared/timer-internal.h
> @@ -0,0 +1,13 @@
> +/*
> + * Copyright (C) 2012 - 2014 Cisco Systems
> + * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
> + * Licensed under the GPL
> + */
> +
> +#ifndef __TIMER_INTERNAL_H__
> +#define __TIMER_INTERNAL_H__
> +
> +#define TIMER_MULTIPLIER 256
> +#define TIMER_MIN_DELTA  500
> +
> +#endif
> diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
> index 68b9119..2ce38c1 100644
> --- a/arch/um/kernel/process.c
> +++ b/arch/um/kernel/process.c
> @@ -27,6 +27,7 @@
>  #include <kern_util.h>
>  #include <os.h>
>  #include <skas.h>
> +#include <timer-internal.h>
>  
>  /*
>   * This is a per-cpu array.  A processor only modifies its entry and it only
> @@ -201,11 +202,8 @@ void initial_thread_cb(void (*proc)(void *), void *arg)
>  
>  void arch_cpu_idle(void)
>  {
> -	unsigned long long nsecs;
> -
>  	cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
> -	nsecs = disable_timer();
> -	idle_sleep(nsecs);
> +	os_idle_sleep(UM_NSEC_PER_SEC);
>  	local_irq_enable();
>  }
>  
> diff --git a/arch/um/kernel/skas/clone.c b/arch/um/kernel/skas/clone.c
> index 289771d..498148b 100644
> --- a/arch/um/kernel/skas/clone.c
> +++ b/arch/um/kernel/skas/clone.c
> @@ -35,11 +35,6 @@ stub_clone_handler(void)
>  	if (err)
>  		goto out;
>  
> -	err = stub_syscall3(__NR_setitimer, ITIMER_VIRTUAL,
> -			    (long) &data->timer, 0);
> -	if (err)
> -		goto out;
> -

By removing this call from our clone stub, you change the way how SKAS0
works. Please explain why this is needed.

>  	remap_stack(data->fd, data->offset);
>  	goto done;
>  
> diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c
> index fda1deb..42e2988 100644
> --- a/arch/um/kernel/skas/mmu.c
> +++ b/arch/um/kernel/skas/mmu.c
> @@ -61,10 +61,12 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm)
>  	if (current->mm != NULL && current->mm != &init_mm)
>  		from_mm = &current->mm->context;
>  
> +	block_signals();
>  	if (from_mm)
>  		to_mm->id.u.pid = copy_context_skas0(stack,
>  						     from_mm->id.u.pid);
>  	else to_mm->id.u.pid = start_userspace(stack);
> +	unblock_signals();

Why do we have to block signals here?

>  	if (to_mm->id.u.pid < 0) {
>  		ret = to_mm->id.u.pid;
> diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c
> index 117568d..29f1125 100644
> --- a/arch/um/kernel/time.c
> +++ b/arch/um/kernel/time.c
> @@ -1,4 +1,5 @@
>  /*
> + * Copyright (C) 2012-2014 Cisco Systems
>   * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
>   * Licensed under the GPL
>   */
> @@ -7,11 +8,15 @@
>  #include <linux/init.h>
>  #include <linux/interrupt.h>
>  #include <linux/jiffies.h>
> +#include <linux/mm.h>
> +#include <linux/sched.h>
> +#include <linux/spinlock.h>
>  #include <linux/threads.h>
>  #include <asm/irq.h>
>  #include <asm/param.h>
>  #include <kern_util.h>
>  #include <os.h>
> +#include <timer-internal.h>
>  
>  void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
>  {
> @@ -22,18 +27,20 @@ void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
>  	local_irq_restore(flags);
>  }
>  
> -static void itimer_set_mode(enum clock_event_mode mode,
> +static void timer_set_mode(enum clock_event_mode mode,
>  			    struct clock_event_device *evt)
>  {
>  	switch (mode) {
>  	case CLOCK_EVT_MODE_PERIODIC:
> -		set_interval();
> +		os_timer_set_interval(NULL, NULL);
>  		break;
>  
> +	case CLOCK_EVT_MODE_ONESHOT:
> +		os_timer_one_shot(1);
> +
>  	case CLOCK_EVT_MODE_SHUTDOWN:
>  	case CLOCK_EVT_MODE_UNUSED:
> -	case CLOCK_EVT_MODE_ONESHOT:
> -		disable_timer();
> +		os_timer_disable();
>  		break;
>  
>  	case CLOCK_EVT_MODE_RESUME:
> @@ -41,68 +48,79 @@ static void itimer_set_mode(enum clock_event_mode mode,
>  	}
>  }
>  
> -static int itimer_next_event(unsigned long delta,
> +static int timer_next_event(unsigned long delta,
>  			     struct clock_event_device *evt)
>  {
> -	return timer_one_shot(delta + 1);
> +	return os_timer_one_shot(delta);

Why did you replace "delta + 1" by "delta"?


>  }
>  
> -static struct clock_event_device itimer_clockevent = {
> -	.name		= "itimer",
> +static struct clock_event_device timer_clockevent = {
> +	.name		= "posix-timer",
>  	.rating		= 250,
>  	.cpumask	= cpu_all_mask,
>  	.features	= CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
> -	.set_mode	= itimer_set_mode,
> -	.set_next_event = itimer_next_event,
> -	.shift		= 32,
> +	.set_mode	= timer_set_mode,
> +	.set_next_event = timer_next_event,
> +	.shift		= 0,
> +	.max_delta_ns	= 0xffffffff,
> +	.min_delta_ns	= TIMER_MIN_DELTA, //microsecond resolution should be enough for anyone, same as 640K RAM
>  	.irq		= 0,
> +	.mult		= 1,
>  };
>  
> -static irqreturn_t um_timer(int irq, void *dev)
> +static irqreturn_t um_timer_irq(int irq, void *dev)
>  {
> -	(*itimer_clockevent.event_handler)(&itimer_clockevent);
> +	if (get_current()->mm != NULL)
> +	{
> +		os_alarm_process(get_current()->mm->context.id.u.pid);
> +	}
> +
> +	(*timer_clockevent.event_handler)(&timer_clockevent);
>  
>  	return IRQ_HANDLED;
>  }
>  
> -static cycle_t itimer_read(struct clocksource *cs)
> +static cycle_t timer_read(struct clocksource *cs)
>  {
> -	return os_nsecs() / 1000;
> +	return os_nsecs() / TIMER_MULTIPLIER;
>  }
>  
> -static struct clocksource itimer_clocksource = {
> -	.name		= "itimer",
> +static struct clocksource timer_clocksource = {
> +	.name		= "timer",
>  	.rating		= 300,
> -	.read		= itimer_read,
> +	.read		= timer_read,
>  	.mask		= CLOCKSOURCE_MASK(64),
>  	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
>  };
>  
> -static void __init setup_itimer(void)
> +static void __init timer_setup(void)
>  {
>  	int err;
>  
> -	err = request_irq(TIMER_IRQ, um_timer, 0, "timer", NULL);
> -	if (err != 0)
> +	err = request_irq(TIMER_IRQ, um_timer_irq, IRQF_TIMER, "hr timer", NULL);
> +	if (err != 0) {
>  		printk(KERN_ERR "register_timer : request_irq failed - "
>  		       "errno = %d\n", -err);
> +		return;
> +    }
> +
> +    err = os_timer_create(NULL);
> +    if (err != 0) {
> +        printk(KERN_ERR "creation of timer failed - errno = %d\n", -err);
> +        return;
> +    }
>  
> -	itimer_clockevent.mult = div_sc(HZ, NSEC_PER_SEC, 32);
> -	itimer_clockevent.max_delta_ns =
> -		clockevent_delta2ns(60 * HZ, &itimer_clockevent);
> -	itimer_clockevent.min_delta_ns =
> -		clockevent_delta2ns(1, &itimer_clockevent);
> -	err = clocksource_register_hz(&itimer_clocksource, USEC_PER_SEC);
> +	err = clocksource_register_hz(&timer_clocksource, NSEC_PER_SEC/TIMER_MULTIPLIER);
>  	if (err) {
>  		printk(KERN_ERR "clocksource_register_hz returned %d\n", err);
>  		return;
>  	}
> -	clockevents_register_device(&itimer_clockevent);
> +	clockevents_register_device(&timer_clockevent);
>  }
>  
>  void read_persistent_clock(struct timespec *ts)
>  {
> -	long long nsecs = os_nsecs();
> +	long long nsecs = os_persistent_clock_emulation();
>  
>  	set_normalized_timespec(ts, nsecs / NSEC_PER_SEC,
>  				nsecs % NSEC_PER_SEC);
> @@ -110,6 +128,6 @@ void read_persistent_clock(struct timespec *ts)
>  
>  void __init time_init(void)
>  {
> -	timer_init();
> -	late_time_init = setup_itimer;
> +	timer_set_signal_handler();
> +	late_time_init = timer_setup;
>  }
> diff --git a/arch/um/os-Linux/internal.h b/arch/um/os-Linux/internal.h
> deleted file mode 100644
> index 0dc2c9f..0000000
> --- a/arch/um/os-Linux/internal.h
> +++ /dev/null
> @@ -1 +0,0 @@
> -void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc);
> diff --git a/arch/um/os-Linux/main.c b/arch/um/os-Linux/main.c
> index df9191a..6e36f0f 100644
> --- a/arch/um/os-Linux/main.c
> +++ b/arch/um/os-Linux/main.c
> @@ -163,13 +163,13 @@ int __init main(int argc, char **argv, char **envp)
>  
>  	/*
>  	 * This signal stuff used to be in the reboot case.  However,
> -	 * sometimes a SIGVTALRM can come in when we're halting (reproducably
> +	 * sometimes a timer signal can come in when we're halting (reproducably
>  	 * when writing out gcov information, presumably because that takes
>  	 * some time) and cause a segfault.
>  	 */
>  
> -	/* stop timers and set SIGVTALRM to be ignored */
> -	disable_timer();
> +	/* stop timers and set timer signal to be ignored */
> +	os_timer_disable();
>  
>  	/* disable SIGIO for the fds and set SIGIO to be ignored */
>  	err = deactivate_all_fds();
> diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c
> index 8408aba..f3bd983 100644
> --- a/arch/um/os-Linux/process.c
> +++ b/arch/um/os-Linux/process.c
> @@ -89,6 +89,11 @@ int os_process_parent(int pid)
>  	return parent;
>  }
>  
> +void os_alarm_process(int pid)
> +{
> +	kill(pid, SIGALRM);
> +}
> +
>  void os_stop_process(int pid)
>  {
>  	kill(pid, SIGSTOP);
> diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
> index 036d0db..e04a4cd 100644
> --- a/arch/um/os-Linux/signal.c
> +++ b/arch/um/os-Linux/signal.c
> @@ -13,7 +13,6 @@
>  #include <kern_util.h>
>  #include <os.h>
>  #include <sysdep/mcontext.h>
> -#include "internal.h"
>  
>  void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
>  	[SIGTRAP]	= relay_signal,
> @@ -23,7 +22,8 @@ void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
>  	[SIGBUS]	= bus_handler,
>  	[SIGSEGV]	= segv_handler,
>  	[SIGIO]		= sigio_handler,
> -	[SIGVTALRM]	= timer_handler };
> +	[SIGALRM]	= timer_handler
> +};
>  
>  static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
>  {
> @@ -38,7 +38,7 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
>  	}
>  
>  	/* enable signals if sig isn't IRQ signal */
> -	if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGVTALRM))
> +	if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGALRM))
>  		unblock_signals();
>  
>  	(*sig_info[sig])(sig, si, &r);
> @@ -55,8 +55,8 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
>  #define SIGIO_BIT 0
>  #define SIGIO_MASK (1 << SIGIO_BIT)
>  
> -#define SIGVTALRM_BIT 1
> -#define SIGVTALRM_MASK (1 << SIGVTALRM_BIT)
> +#define SIGALRM_BIT 1
> +#define SIGALRM_MASK (1 << SIGALRM_BIT)
>  
>  static int signals_enabled;
>  static unsigned int signals_pending;
> @@ -78,36 +78,34 @@ void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
>  	set_signals(enabled);
>  }
>  
> -static void real_alarm_handler(mcontext_t *mc)
> +static void timer_real_alarm_handler(mcontext_t *mc)
>  {
>  	struct uml_pt_regs regs;
>  
>  	if (mc != NULL)
>  		get_regs_from_mc(&regs, mc);
> -	regs.is_user = 0;
> -	unblock_signals();
> -	timer_handler(SIGVTALRM, NULL, &regs);
> +	timer_handler(SIGALRM, NULL, &regs);
>  }
>  
> -void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
> +void timer_alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
>  {
>  	int enabled;
>  
>  	enabled = signals_enabled;
>  	if (!signals_enabled) {
> -		signals_pending |= SIGVTALRM_MASK;
> +		signals_pending |= SIGALRM_MASK;
>  		return;
>  	}
>  
>  	block_signals();
>  
> -	real_alarm_handler(mc);
> +	timer_real_alarm_handler(mc);
>  	set_signals(enabled);
>  }
>  
> -void timer_init(void)
> +void timer_set_signal_handler(void)
>  {
> -	set_handler(SIGVTALRM);
> +	set_handler(SIGALRM);
>  }
>  
>  void set_sigstack(void *sig_stack, int size)
> @@ -131,10 +129,9 @@ static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
>  
>  	[SIGIO] = sig_handler,
>  	[SIGWINCH] = sig_handler,
> -	[SIGVTALRM] = alarm_handler
> +	[SIGALRM] = timer_alarm_handler
>  };
>  
> -
>  static void hard_handler(int sig, siginfo_t *si, void *p)
>  {
>  	struct ucontext *uc = p;
> @@ -188,9 +185,9 @@ void set_handler(int sig)
>  
>  	/* block irq ones */
>  	sigemptyset(&action.sa_mask);
> -	sigaddset(&action.sa_mask, SIGVTALRM);
>  	sigaddset(&action.sa_mask, SIGIO);
>  	sigaddset(&action.sa_mask, SIGWINCH);
> +	sigaddset(&action.sa_mask, SIGALRM);
>  
>  	if (sig == SIGSEGV)
>  		flags |= SA_NODEFER;
> @@ -283,8 +280,8 @@ void unblock_signals(void)
>  		if (save_pending & SIGIO_MASK)
>  			sig_handler_common(SIGIO, NULL, NULL);
>  
> -		if (save_pending & SIGVTALRM_MASK)
> -			real_alarm_handler(NULL);
> +		if (save_pending & SIGALRM_MASK)
> +			timer_real_alarm_handler(NULL);
>  	}
>  }
>  
> diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
> index 3dddedb..5ae4752 100644
> --- a/arch/um/os-Linux/skas/process.c
> +++ b/arch/um/os-Linux/skas/process.c
> @@ -45,7 +45,7 @@ static int ptrace_dump_regs(int pid)
>   * Signals that are OK to receive in the stub - we'll just continue it.
>   * SIGWINCH will happen when UML is inside a detached screen.
>   */
> -#define STUB_SIG_MASK ((1 << SIGVTALRM) | (1 << SIGWINCH))
> +#define STUB_SIG_MASK ((1 << SIGALRM) | (1 << SIGWINCH))
>  
>  /* Signals that the stub will finish with - anything else is an error */
>  #define STUB_DONE_MASK (1 << SIGTRAP)
> @@ -179,19 +179,13 @@ extern char __syscall_stub_start[];
>  static int userspace_tramp(void *stack)
>  {
>  	void *addr;
> -	int err, fd;
> +	int fd;
>  	unsigned long long offset;
>  
>  	ptrace(PTRACE_TRACEME, 0, 0, 0);
>  
>  	signal(SIGTERM, SIG_DFL);
>  	signal(SIGWINCH, SIG_IGN);
> -	err = set_interval();
> -	if (err) {
> -		printk(UM_KERN_ERR "userspace_tramp - setting timer failed, "
> -		       "errno = %d\n", err);
> -		exit(1);
> -	}
>  
>  	/*
>  	 * This has a pte, but it can't be mapped in with the usual
> @@ -282,7 +276,7 @@ int start_userspace(unsigned long stub_stack)
>  			       "errno = %d\n", errno);
>  			goto out_kill;
>  		}
> -	} while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGVTALRM));
> +	} while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGALRM));
>  
>  	if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
>  		err = -EINVAL;
> @@ -315,8 +309,6 @@ int start_userspace(unsigned long stub_stack)
>  
>  void userspace(struct uml_pt_regs *regs)
>  {
> -	struct itimerval timer;
> -	unsigned long long nsecs, now;
>  	int err, status, op, pid = userspace_pid[0];
>  	/* To prevent races if using_sysemu changes under us.*/
>  	int local_using_sysemu;
> @@ -325,13 +317,8 @@ void userspace(struct uml_pt_regs *regs)
>  	/* Handle any immediate reschedules or signals */
>  	interrupt_end();
>  
> -	if (getitimer(ITIMER_VIRTUAL, &timer))
> -		printk(UM_KERN_ERR "Failed to get itimer, errno = %d\n", errno);
> -	nsecs = timer.it_value.tv_sec * UM_NSEC_PER_SEC +
> -		timer.it_value.tv_usec * UM_NSEC_PER_USEC;
> -	nsecs += os_nsecs();
> -
>  	while (1) {
> +
>  		/*
>  		 * This can legitimately fail if the process loads a
>  		 * bogus value into a segment register.  It will
> @@ -401,18 +388,7 @@ void userspace(struct uml_pt_regs *regs)
>  			case SIGTRAP:
>  				relay_signal(SIGTRAP, (struct siginfo *)&si, regs);
>  				break;
> -			case SIGVTALRM:
> -				now = os_nsecs();
> -				if (now < nsecs)
> -					break;
> -				block_signals();
> -				(*sig_info[sig])(sig, (struct siginfo *)&si, regs);
> -				unblock_signals();
> -				nsecs = timer.it_value.tv_sec *
> -					UM_NSEC_PER_SEC +
> -					timer.it_value.tv_usec *
> -					UM_NSEC_PER_USEC;
> -				nsecs += os_nsecs();
> +			case SIGALRM:
>  				break;
>  			case SIGIO:
>  			case SIGILL:
> @@ -460,7 +436,6 @@ __initcall(init_thread_regs);
>  
>  int copy_context_skas0(unsigned long new_stack, int pid)
>  {
> -	struct timeval tv = { .tv_sec = 0, .tv_usec = UM_USEC_PER_SEC / UM_HZ };
>  	int err;
>  	unsigned long current_stack = current_stub_stack();
>  	struct stub_data *data = (struct stub_data *) current_stack;
> @@ -472,11 +447,10 @@ int copy_context_skas0(unsigned long new_stack, int pid)
>  	 * prepare offset and fd of child's stack as argument for parent's
>  	 * and child's mmap2 calls
>  	 */
> -	*data = ((struct stub_data) { .offset	= MMAP_OFFSET(new_offset),
> -				      .fd	= new_fd,
> -				      .timer    = ((struct itimerval)
> -					           { .it_value = tv,
> -						     .it_interval = tv }) });
> +	*data = ((struct stub_data) { 
> +			.offset	= MMAP_OFFSET(new_offset),
> +			.fd     = new_fd
> +	});

As written above, you change the way how SKAS0 works, this needs
much more explaination.

>  	err = ptrace_setregs(pid, thread_regs);
>  	if (err < 0) {
> diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c
> index e9824d5..0e2bb7d 100644
> --- a/arch/um/os-Linux/time.c
> +++ b/arch/um/os-Linux/time.c
> @@ -1,4 +1,5 @@
>  /*
> + * Copyright (C) 2012-2014 Cisco Systems
>   * Copyright (C) 2000 - 2007 Jeff Dike (jdike{addtoit,linux.intel}.com)
>   * Licensed under the GPL
>   */
> @@ -10,177 +11,172 @@
>  #include <sys/time.h>
>  #include <kern_util.h>
>  #include <os.h>
> -#include "internal.h"
> +#include <string.h>
> +#include <timer-internal.h>
>  
> -int set_interval(void)
> -{
> -	int usec = UM_USEC_PER_SEC / UM_HZ;
> -	struct itimerval interval = ((struct itimerval) { { 0, usec },
> -							  { 0, usec } });
> -
> -	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
> -		return -errno;
> +static timer_t event_high_res_timer = 0;
>  
> -	return 0;
> +static inline long long timeval_to_ns(const struct timeval *tv)
> +{
> +	return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
> +		tv->tv_usec * UM_NSEC_PER_USEC;
>  }
>  
> -int timer_one_shot(int ticks)
> +static inline long long timespec_to_ns(const struct timespec *ts)
>  {
> -	unsigned long usec = ticks * UM_USEC_PER_SEC / UM_HZ;
> -	unsigned long sec = usec / UM_USEC_PER_SEC;
> -	struct itimerval interval;
> -
> -	usec %= UM_USEC_PER_SEC;
> -	interval = ((struct itimerval) { { 0, 0 }, { sec, usec } });
> +	return ((long long) ts->tv_sec * UM_NSEC_PER_SEC) +
> +		ts->tv_nsec;
> +}
>  
> -	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
> -		return -errno;
> +long long os_persistent_clock_emulation (void) {
> +	struct timespec realtime_tp;
>  
> -	return 0;
> +	clock_gettime(CLOCK_REALTIME, &realtime_tp);
> +	return timespec_to_ns(&realtime_tp);
>  }
>  
>  /**
> - * timeval_to_ns - Convert timeval to nanoseconds
> - * @ts:		pointer to the timeval variable to be converted
> - *
> - * Returns the scalar nanosecond representation of the timeval
> - * parameter.
> - *
> - * Ripped from linux/time.h because it's a kernel header, and thus
> - * unusable from here.
> + * os_timer_create() - create an new posix (interval) timer
>   */
> -static inline long long timeval_to_ns(const struct timeval *tv)
> -{
> -	return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
> -		tv->tv_usec * UM_NSEC_PER_USEC;
> +int os_timer_create(void* timer) {
> +
> +	timer_t* t = timer;
> +
> +	if(t == NULL) {
> +		t = &event_high_res_timer;
> +	}
> +
> +	if (timer_create(
> +		CLOCK_MONOTONIC,
> +		NULL,
> +		t) == -1) {
> +		return -1;
> +	}
> +	return 0;
>  }
>  
> -long long disable_timer(void)
> +int os_timer_set_interval(void* timer, void* i)
>  {
> -	struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } });
> -	long long remain, max = UM_NSEC_PER_SEC / UM_HZ;
> +	struct itimerspec its;
> +	unsigned long long nsec;
> +	timer_t* t = timer;
> +	struct itimerspec* its_in = i;
>  
> -	if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0)
> -		printk(UM_KERN_ERR "disable_timer - setitimer failed, "
> -		       "errno = %d\n", errno);
> +	if(t == NULL) {
> +		t = &event_high_res_timer;
> +	}
>  
> -	remain = timeval_to_ns(&time.it_value);
> -	if (remain > max)
> -		remain = max;
> +	nsec = UM_NSEC_PER_SEC / UM_HZ;
>  
> -	return remain;
> -}
> +	if(its_in != NULL) {
> +		its.it_value.tv_sec = its_in->it_value.tv_sec;
> +		its.it_value.tv_nsec = its_in->it_value.tv_nsec;
> +	} else {
> +		its.it_value.tv_sec = 0;
> +		its.it_value.tv_nsec = nsec;
> +	}
>  
> -long long os_nsecs(void)
> -{
> -	struct timeval tv;
> +	its.it_interval.tv_sec = 0;
> +	its.it_interval.tv_nsec = nsec;
>  
> -	gettimeofday(&tv, NULL);
> -	return timeval_to_ns(&tv);
> -}
> +	if(timer_settime(*t, 0, &its, NULL) == -1) {
> +		return -errno;
> +	}
>  
> -#ifdef UML_CONFIG_NO_HZ_COMMON
> -static int after_sleep_interval(struct timespec *ts)
> -{
>  	return 0;
>  }
>  
> -static void deliver_alarm(void)
> +/**
> + * os_timer_remain() - returns the remaining nano seconds of the given interval
> + *                     timer
> + * Because this is the remaining time of an interval timer, which correspondends
> + * to HZ, this value can never be bigger than one second. Just
> + * the nanosecond part of the timer is returned.
> + * The returned time is relative to the start time of the interval timer.
> + * Return an negative value in an error case.
> + */
> +long os_timer_remain(void* timer)
>  {
> -	alarm_handler(SIGVTALRM, NULL, NULL);
> -}
> +	struct itimerspec its;
> +	timer_t* t = timer;
>  
> -static unsigned long long sleep_time(unsigned long long nsecs)
> -{
> -	return nsecs;
> -}
> +	if(t == NULL) {
> +		t = &event_high_res_timer;
> +	}
>  
> -#else
> -unsigned long long last_tick;
> -unsigned long long skew;
> +	if(timer_gettime(t, &its) == -1) {
> +		return -errno;
> +	}
> +
> +	return its.it_value.tv_nsec;
> +}
>  
> -static void deliver_alarm(void)
> +int os_timer_one_shot(int ticks)
>  {
> -	unsigned long long this_tick = os_nsecs();
> -	int one_tick = UM_NSEC_PER_SEC / UM_HZ;
> +	struct itimerspec its;
> +	unsigned long long nsec;
> +	unsigned long sec;
>  
> -	/* Protection against the host's time going backwards */
> -	if ((last_tick != 0) && (this_tick < last_tick))
> -		this_tick = last_tick;
> +    nsec = (ticks + 1);
> +    sec = nsec / UM_NSEC_PER_SEC;
> +	nsec = nsec % UM_NSEC_PER_SEC;
>  
> -	if (last_tick == 0)
> -		last_tick = this_tick - one_tick;
> +	its.it_value.tv_sec = nsec / UM_NSEC_PER_SEC;
> +	its.it_value.tv_nsec = nsec;
>  
> -	skew += this_tick - last_tick;
> +	its.it_interval.tv_sec = 0;
> +	its.it_interval.tv_nsec = 0; // we cheat here
>  
> -	while (skew >= one_tick) {
> -		alarm_handler(SIGVTALRM, NULL, NULL);
> -		skew -= one_tick;
> -	}
> -
> -	last_tick = this_tick;
> +	timer_settime(event_high_res_timer, 0, &its, NULL);
> +	return 0;
>  }
>  
> -static unsigned long long sleep_time(unsigned long long nsecs)
> +/**
> + * os_timer_disable() - disable the posix (interval) timer
> + * Returns the remaining interval timer time in nanoseconds
> + */
> +long long os_timer_disable(void)
>  {
> -	return nsecs > skew ? nsecs - skew : 0;
> +	struct itimerspec its;
> +
> +	memset(&its, 0, sizeof(struct itimerspec));
> +	timer_settime(event_high_res_timer, 0, &its, &its);
> +
> +	return its.it_value.tv_sec * UM_NSEC_PER_SEC + its.it_value.tv_nsec;
>  }
>  
> -static inline long long timespec_to_us(const struct timespec *ts)
> +long long os_vnsecs(void)
>  {
> -	return ((long long) ts->tv_sec * UM_USEC_PER_SEC) +
> -		ts->tv_nsec / UM_NSEC_PER_USEC;
> +	struct timespec ts;
> +
> +	clock_gettime(CLOCK_PROCESS_CPUTIME_ID,&ts);
> +	return timespec_to_ns(&ts);
>  }
>  
> -static int after_sleep_interval(struct timespec *ts)
> +long long os_nsecs(void)
>  {
> -	int usec = UM_USEC_PER_SEC / UM_HZ;
> -	long long start_usecs = timespec_to_us(ts);
> -	struct timeval tv;
> -	struct itimerval interval;
> -
> -	/*
> -	 * It seems that rounding can increase the value returned from
> -	 * setitimer to larger than the one passed in.  Over time,
> -	 * this will cause the remaining time to be greater than the
> -	 * tick interval.  If this happens, then just reduce the first
> -	 * tick to the interval value.
> -	 */
> -	if (start_usecs > usec)
> -		start_usecs = usec;
> -
> -	start_usecs -= skew / UM_NSEC_PER_USEC;
> -	if (start_usecs < 0)
> -		start_usecs = 0;
> -
> -	tv = ((struct timeval) { .tv_sec  = start_usecs / UM_USEC_PER_SEC,
> -				 .tv_usec = start_usecs % UM_USEC_PER_SEC });
> -	interval = ((struct itimerval) { { 0, usec }, tv });
> -
> -	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
> -		return -errno;
> +	struct timespec ts;
>  
> -	return 0;
> +	clock_gettime(CLOCK_MONOTONIC,&ts);
> +	return timespec_to_ns(&ts);
>  }
> -#endif
>  
> -void idle_sleep(unsigned long long nsecs)
> +/**
> + * os_idle_sleep() - sleep for a given time of nsecs
> + * @nsecs: nanoseconds to sleep
> + */
> +void os_idle_sleep(unsigned long long nsecs)
>  {
>  	struct timespec ts;
>  
> -	/*
> -	 * nsecs can come in as zero, in which case, this starts a
> -	 * busy loop.  To prevent this, reset nsecs to the tick
> -	 * interval if it is zero.
> -	 */
> -	if (nsecs == 0)
> -		nsecs = UM_NSEC_PER_SEC / UM_HZ;
> -
> -	nsecs = sleep_time(nsecs);
> -	ts = ((struct timespec) { .tv_sec	= nsecs / UM_NSEC_PER_SEC,
> -				  .tv_nsec	= nsecs % UM_NSEC_PER_SEC });
> -
> -	if (nanosleep(&ts, &ts) == 0)
> -		deliver_alarm();
> -	after_sleep_interval(&ts);
> +	if (nsecs <= 0) {
> +		return;
> +	}
> +
> +	ts = ((struct timespec) {
> +			.tv_sec  = nsecs / UM_NSEC_PER_SEC,
> +			.tv_nsec = nsecs % UM_NSEC_PER_SEC
> +	});
> +
> +	clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, NULL);
>  }
> 

Thanks,
//richard

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[uml-devel] [PATCH] um: Switch clocksource to hrtimers

[Thomas Meyer]

Switch the UML clocksource from interval timers to posix interval timers and
move to a monotonic timer.

This fixes suspend&resume related timer issues and improves network performance
as TCP state machines are now fed with the correct time; also correct QoS and
traffic shaping.

Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
---
 arch/um/Makefile                        |   2 +-
 arch/um/include/shared/os.h             |  15 +-
 arch/um/include/shared/skas/stub-data.h |   5 +-
 arch/um/include/shared/timer-internal.h |  13 ++
 arch/um/kernel/process.c                |   6 +-
 arch/um/kernel/skas/clone.c             |   5 -
 arch/um/kernel/skas/mmu.c               |   2 +
 arch/um/kernel/time.c                   |  80 +++++++----
 arch/um/os-Linux/internal.h             |   1 -
 arch/um/os-Linux/main.c                 |   6 +-
 arch/um/os-Linux/process.c              |   5 +
 arch/um/os-Linux/signal.c               |  35 +++--
 arch/um/os-Linux/skas/process.c         |  44 ++----
 arch/um/os-Linux/time.c                 | 248 ++++++++++++++++----------------
 14 files changed, 234 insertions(+), 233 deletions(-)
 create mode 100644 arch/um/include/shared/timer-internal.h
 delete mode 100644 arch/um/os-Linux/internal.h

diff --git a/arch/um/Makefile b/arch/um/Makefile
index 098ab33..eb79b4b 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -131,7 +131,7 @@ export LDS_ELF_FORMAT := $(ELF_FORMAT)
 # The wrappers will select whether using "malloc" or the kernel allocator.
 LINK_WRAPS = -Wl,--wrap,malloc -Wl,--wrap,free -Wl,--wrap,calloc
 
-LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt))
+LD_FLAGS_CMDLINE = $(foreach opt,$(LDFLAGS),-Wl,$(opt)) -lrt
 
 # Used by link-vmlinux.sh which has special support for um link
 export CFLAGS_vmlinux := $(LINK-y) $(LINK_WRAPS) $(LD_FLAGS_CMDLINE)
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index ad3fa3a..7519c98 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -183,6 +183,7 @@ extern int create_mem_file(unsigned long long len);
 /* process.c */
 extern unsigned long os_process_pc(int pid);
 extern int os_process_parent(int pid);
+extern void os_alarm_process(int pid);
 extern void os_stop_process(int pid);
 extern void os_kill_process(int pid, int reap_child);
 extern void os_kill_ptraced_process(int pid, int reap_child);
@@ -217,7 +218,7 @@ extern int set_umid(char *name);
 extern char *get_umid(void);
 
 /* signal.c */
-extern void timer_init(void);
+extern void timer_set_signal_handler(void);
 extern void set_sigstack(void *sig_stack, int size);
 extern void remove_sigstack(void);
 extern void set_handler(int sig);
@@ -238,12 +239,16 @@ extern void um_early_printk(const char *s, unsigned int n);
 extern void os_fix_helper_signals(void);
 
 /* time.c */
-extern void idle_sleep(unsigned long long nsecs);
-extern int set_interval(void);
-extern int timer_one_shot(int ticks);
-extern long long disable_timer(void);
+extern void os_idle_sleep(unsigned long long nsecs);
+extern int os_timer_create(void* timer);
+extern int os_timer_set_interval(void* timer, void* its);
+extern int os_timer_one_shot(int ticks);
+extern long long os_timer_disable(void);
+extern long os_timer_remain(void* timer);
 extern void uml_idle_timer(void);
+extern long long os_persistent_clock_emulation(void);
 extern long long os_nsecs(void);
+extern long long os_vnsecs(void);
 
 /* skas/mem.c */
 extern long run_syscall_stub(struct mm_id * mm_idp,
diff --git a/arch/um/include/shared/skas/stub-data.h b/arch/um/include/shared/skas/stub-data.h
index f6ed92c..e09d8fd 100644
--- a/arch/um/include/shared/skas/stub-data.h
+++ b/arch/um/include/shared/skas/stub-data.h
@@ -6,12 +6,11 @@
 #ifndef __STUB_DATA_H
 #define __STUB_DATA_H
 
-#include <sys/time.h>
+#include <time.h>
 
 struct stub_data {
-	long offset;
+	unsigned long offset;
 	int fd;
-	struct itimerval timer;
 	long err;
 };
 
diff --git a/arch/um/include/shared/timer-internal.h b/arch/um/include/shared/timer-internal.h
new file mode 100644
index 0000000..03e6f21
--- /dev/null
+++ b/arch/um/include/shared/timer-internal.h
@@ -0,0 +1,13 @@
+/*
+ * Copyright (C) 2012 - 2014 Cisco Systems
+ * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ */
+
+#ifndef __TIMER_INTERNAL_H__
+#define __TIMER_INTERNAL_H__
+
+#define TIMER_MULTIPLIER 256
+#define TIMER_MIN_DELTA  500
+
+#endif
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index 68b9119..2ce38c1 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -27,6 +27,7 @@
 #include <kern_util.h>
 #include <os.h>
 #include <skas.h>
+#include <timer-internal.h>
 
 /*
  * This is a per-cpu array.  A processor only modifies its entry and it only
@@ -201,11 +202,8 @@ void initial_thread_cb(void (*proc)(void *), void *arg)
 
 void arch_cpu_idle(void)
 {
-	unsigned long long nsecs;
-
 	cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
-	nsecs = disable_timer();
-	idle_sleep(nsecs);
+	os_idle_sleep(UM_NSEC_PER_SEC);
 	local_irq_enable();
 }
 
diff --git a/arch/um/kernel/skas/clone.c b/arch/um/kernel/skas/clone.c
index 289771d..498148b 100644
--- a/arch/um/kernel/skas/clone.c
+++ b/arch/um/kernel/skas/clone.c
@@ -35,11 +35,6 @@ stub_clone_handler(void)
 	if (err)
 		goto out;
 
-	err = stub_syscall3(__NR_setitimer, ITIMER_VIRTUAL,
-			    (long) &data->timer, 0);
-	if (err)
-		goto out;
-
 	remap_stack(data->fd, data->offset);
 	goto done;
 
diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c
index fda1deb..42e2988 100644
--- a/arch/um/kernel/skas/mmu.c
+++ b/arch/um/kernel/skas/mmu.c
@@ -61,10 +61,12 @@ int init_new_context(struct task_struct *task, struct mm_struct *mm)
 	if (current->mm != NULL && current->mm != &init_mm)
 		from_mm = &current->mm->context;
 
+	block_signals();
 	if (from_mm)
 		to_mm->id.u.pid = copy_context_skas0(stack,
 						     from_mm->id.u.pid);
 	else to_mm->id.u.pid = start_userspace(stack);
+	unblock_signals();
 
 	if (to_mm->id.u.pid < 0) {
 		ret = to_mm->id.u.pid;
diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c
index 117568d..29f1125 100644
--- a/arch/um/kernel/time.c
+++ b/arch/um/kernel/time.c
@@ -1,4 +1,5 @@
 /*
+ * Copyright (C) 2012-2014 Cisco Systems
  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  * Licensed under the GPL
  */
@@ -7,11 +8,15 @@
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/jiffies.h>
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
 #include <linux/threads.h>
 #include <asm/irq.h>
 #include <asm/param.h>
 #include <kern_util.h>
 #include <os.h>
+#include <timer-internal.h>
 
 void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
 {
@@ -22,18 +27,20 @@ void timer_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
 	local_irq_restore(flags);
 }
 
-static void itimer_set_mode(enum clock_event_mode mode,
+static void timer_set_mode(enum clock_event_mode mode,
 			    struct clock_event_device *evt)
 {
 	switch (mode) {
 	case CLOCK_EVT_MODE_PERIODIC:
-		set_interval();
+		os_timer_set_interval(NULL, NULL);
 		break;
 
+	case CLOCK_EVT_MODE_ONESHOT:
+		os_timer_one_shot(1);
+
 	case CLOCK_EVT_MODE_SHUTDOWN:
 	case CLOCK_EVT_MODE_UNUSED:
-	case CLOCK_EVT_MODE_ONESHOT:
-		disable_timer();
+		os_timer_disable();
 		break;
 
 	case CLOCK_EVT_MODE_RESUME:
@@ -41,68 +48,79 @@ static void itimer_set_mode(enum clock_event_mode mode,
 	}
 }
 
-static int itimer_next_event(unsigned long delta,
+static int timer_next_event(unsigned long delta,
 			     struct clock_event_device *evt)
 {
-	return timer_one_shot(delta + 1);
+	return os_timer_one_shot(delta);
 }
 
-static struct clock_event_device itimer_clockevent = {
-	.name		= "itimer",
+static struct clock_event_device timer_clockevent = {
+	.name		= "posix-timer",
 	.rating		= 250,
 	.cpumask	= cpu_all_mask,
 	.features	= CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
-	.set_mode	= itimer_set_mode,
-	.set_next_event = itimer_next_event,
-	.shift		= 32,
+	.set_mode	= timer_set_mode,
+	.set_next_event = timer_next_event,
+	.shift		= 0,
+	.max_delta_ns	= 0xffffffff,
+	.min_delta_ns	= TIMER_MIN_DELTA, //microsecond resolution should be enough for anyone, same as 640K RAM
 	.irq		= 0,
+	.mult		= 1,
 };
 
-static irqreturn_t um_timer(int irq, void *dev)
+static irqreturn_t um_timer_irq(int irq, void *dev)
 {
-	(*itimer_clockevent.event_handler)(&itimer_clockevent);
+	if (get_current()->mm != NULL)
+	{
+		os_alarm_process(get_current()->mm->context.id.u.pid);
+	}
+
+	(*timer_clockevent.event_handler)(&timer_clockevent);
 
 	return IRQ_HANDLED;
 }
 
-static cycle_t itimer_read(struct clocksource *cs)
+static cycle_t timer_read(struct clocksource *cs)
 {
-	return os_nsecs() / 1000;
+	return os_nsecs() / TIMER_MULTIPLIER;
 }
 
-static struct clocksource itimer_clocksource = {
-	.name		= "itimer",
+static struct clocksource timer_clocksource = {
+	.name		= "timer",
 	.rating		= 300,
-	.read		= itimer_read,
+	.read		= timer_read,
 	.mask		= CLOCKSOURCE_MASK(64),
 	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
-static void __init setup_itimer(void)
+static void __init timer_setup(void)
 {
 	int err;
 
-	err = request_irq(TIMER_IRQ, um_timer, 0, "timer", NULL);
-	if (err != 0)
+	err = request_irq(TIMER_IRQ, um_timer_irq, IRQF_TIMER, "hr timer", NULL);
+	if (err != 0) {
 		printk(KERN_ERR "register_timer : request_irq failed - "
 		       "errno = %d\n", -err);
+		return;
+    }
+
+    err = os_timer_create(NULL);
+    if (err != 0) {
+        printk(KERN_ERR "creation of timer failed - errno = %d\n", -err);
+        return;
+    }
 
-	itimer_clockevent.mult = div_sc(HZ, NSEC_PER_SEC, 32);
-	itimer_clockevent.max_delta_ns =
-		clockevent_delta2ns(60 * HZ, &itimer_clockevent);
-	itimer_clockevent.min_delta_ns =
-		clockevent_delta2ns(1, &itimer_clockevent);
-	err = clocksource_register_hz(&itimer_clocksource, USEC_PER_SEC);
+	err = clocksource_register_hz(&timer_clocksource, NSEC_PER_SEC/TIMER_MULTIPLIER);
 	if (err) {
 		printk(KERN_ERR "clocksource_register_hz returned %d\n", err);
 		return;
 	}
-	clockevents_register_device(&itimer_clockevent);
+	clockevents_register_device(&timer_clockevent);
 }
 
 void read_persistent_clock(struct timespec *ts)
 {
-	long long nsecs = os_nsecs();
+	long long nsecs = os_persistent_clock_emulation();
 
 	set_normalized_timespec(ts, nsecs / NSEC_PER_SEC,
 				nsecs % NSEC_PER_SEC);
@@ -110,6 +128,6 @@ void read_persistent_clock(struct timespec *ts)
 
 void __init time_init(void)
 {
-	timer_init();
-	late_time_init = setup_itimer;
+	timer_set_signal_handler();
+	late_time_init = timer_setup;
 }
diff --git a/arch/um/os-Linux/internal.h b/arch/um/os-Linux/internal.h
deleted file mode 100644
index 0dc2c9f..0000000
--- a/arch/um/os-Linux/internal.h
+++ /dev/null
@@ -1 +0,0 @@
-void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc);
diff --git a/arch/um/os-Linux/main.c b/arch/um/os-Linux/main.c
index df9191a..6e36f0f 100644
--- a/arch/um/os-Linux/main.c
+++ b/arch/um/os-Linux/main.c
@@ -163,13 +163,13 @@ int __init main(int argc, char **argv, char **envp)
 
 	/*
 	 * This signal stuff used to be in the reboot case.  However,
-	 * sometimes a SIGVTALRM can come in when we're halting (reproducably
+	 * sometimes a timer signal can come in when we're halting (reproducably
 	 * when writing out gcov information, presumably because that takes
 	 * some time) and cause a segfault.
 	 */
 
-	/* stop timers and set SIGVTALRM to be ignored */
-	disable_timer();
+	/* stop timers and set timer signal to be ignored */
+	os_timer_disable();
 
 	/* disable SIGIO for the fds and set SIGIO to be ignored */
 	err = deactivate_all_fds();
diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c
index 8408aba..f3bd983 100644
--- a/arch/um/os-Linux/process.c
+++ b/arch/um/os-Linux/process.c
@@ -89,6 +89,11 @@ int os_process_parent(int pid)
 	return parent;
 }
 
+void os_alarm_process(int pid)
+{
+	kill(pid, SIGALRM);
+}
+
 void os_stop_process(int pid)
 {
 	kill(pid, SIGSTOP);
diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
index 036d0db..e04a4cd 100644
--- a/arch/um/os-Linux/signal.c
+++ b/arch/um/os-Linux/signal.c
@@ -13,7 +13,6 @@
 #include <kern_util.h>
 #include <os.h>
 #include <sysdep/mcontext.h>
-#include "internal.h"
 
 void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
 	[SIGTRAP]	= relay_signal,
@@ -23,7 +22,8 @@ void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *) = {
 	[SIGBUS]	= bus_handler,
 	[SIGSEGV]	= segv_handler,
 	[SIGIO]		= sigio_handler,
-	[SIGVTALRM]	= timer_handler };
+	[SIGALRM]	= timer_handler
+};
 
 static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
 {
@@ -38,7 +38,7 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
 	}
 
 	/* enable signals if sig isn't IRQ signal */
-	if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGVTALRM))
+	if ((sig != SIGIO) && (sig != SIGWINCH) && (sig != SIGALRM))
 		unblock_signals();
 
 	(*sig_info[sig])(sig, si, &r);
@@ -55,8 +55,8 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc)
 #define SIGIO_BIT 0
 #define SIGIO_MASK (1 << SIGIO_BIT)
 
-#define SIGVTALRM_BIT 1
-#define SIGVTALRM_MASK (1 << SIGVTALRM_BIT)
+#define SIGALRM_BIT 1
+#define SIGALRM_MASK (1 << SIGALRM_BIT)
 
 static int signals_enabled;
 static unsigned int signals_pending;
@@ -78,36 +78,34 @@ void sig_handler(int sig, struct siginfo *si, mcontext_t *mc)
 	set_signals(enabled);
 }
 
-static void real_alarm_handler(mcontext_t *mc)
+static void timer_real_alarm_handler(mcontext_t *mc)
 {
 	struct uml_pt_regs regs;
 
 	if (mc != NULL)
 		get_regs_from_mc(&regs, mc);
-	regs.is_user = 0;
-	unblock_signals();
-	timer_handler(SIGVTALRM, NULL, &regs);
+	timer_handler(SIGALRM, NULL, &regs);
 }
 
-void alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
+void timer_alarm_handler(int sig, struct siginfo *unused_si, mcontext_t *mc)
 {
 	int enabled;
 
 	enabled = signals_enabled;
 	if (!signals_enabled) {
-		signals_pending |= SIGVTALRM_MASK;
+		signals_pending |= SIGALRM_MASK;
 		return;
 	}
 
 	block_signals();
 
-	real_alarm_handler(mc);
+	timer_real_alarm_handler(mc);
 	set_signals(enabled);
 }
 
-void timer_init(void)
+void timer_set_signal_handler(void)
 {
-	set_handler(SIGVTALRM);
+	set_handler(SIGALRM);
 }
 
 void set_sigstack(void *sig_stack, int size)
@@ -131,10 +129,9 @@ static void (*handlers[_NSIG])(int sig, struct siginfo *si, mcontext_t *mc) = {
 
 	[SIGIO] = sig_handler,
 	[SIGWINCH] = sig_handler,
-	[SIGVTALRM] = alarm_handler
+	[SIGALRM] = timer_alarm_handler
 };
 
-
 static void hard_handler(int sig, siginfo_t *si, void *p)
 {
 	struct ucontext *uc = p;
@@ -188,9 +185,9 @@ void set_handler(int sig)
 
 	/* block irq ones */
 	sigemptyset(&action.sa_mask);
-	sigaddset(&action.sa_mask, SIGVTALRM);
 	sigaddset(&action.sa_mask, SIGIO);
 	sigaddset(&action.sa_mask, SIGWINCH);
+	sigaddset(&action.sa_mask, SIGALRM);
 
 	if (sig == SIGSEGV)
 		flags |= SA_NODEFER;
@@ -283,8 +280,8 @@ void unblock_signals(void)
 		if (save_pending & SIGIO_MASK)
 			sig_handler_common(SIGIO, NULL, NULL);
 
-		if (save_pending & SIGVTALRM_MASK)
-			real_alarm_handler(NULL);
+		if (save_pending & SIGALRM_MASK)
+			timer_real_alarm_handler(NULL);
 	}
 }
 
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index 3dddedb..5ae4752 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -45,7 +45,7 @@ static int ptrace_dump_regs(int pid)
  * Signals that are OK to receive in the stub - we'll just continue it.
  * SIGWINCH will happen when UML is inside a detached screen.
  */
-#define STUB_SIG_MASK ((1 << SIGVTALRM) | (1 << SIGWINCH))
+#define STUB_SIG_MASK ((1 << SIGALRM) | (1 << SIGWINCH))
 
 /* Signals that the stub will finish with - anything else is an error */
 #define STUB_DONE_MASK (1 << SIGTRAP)
@@ -179,19 +179,13 @@ extern char __syscall_stub_start[];
 static int userspace_tramp(void *stack)
 {
 	void *addr;
-	int err, fd;
+	int fd;
 	unsigned long long offset;
 
 	ptrace(PTRACE_TRACEME, 0, 0, 0);
 
 	signal(SIGTERM, SIG_DFL);
 	signal(SIGWINCH, SIG_IGN);
-	err = set_interval();
-	if (err) {
-		printk(UM_KERN_ERR "userspace_tramp - setting timer failed, "
-		       "errno = %d\n", err);
-		exit(1);
-	}
 
 	/*
 	 * This has a pte, but it can't be mapped in with the usual
@@ -282,7 +276,7 @@ int start_userspace(unsigned long stub_stack)
 			       "errno = %d\n", errno);
 			goto out_kill;
 		}
-	} while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGVTALRM));
+	} while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGALRM));
 
 	if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
 		err = -EINVAL;
@@ -315,8 +309,6 @@ int start_userspace(unsigned long stub_stack)
 
 void userspace(struct uml_pt_regs *regs)
 {
-	struct itimerval timer;
-	unsigned long long nsecs, now;
 	int err, status, op, pid = userspace_pid[0];
 	/* To prevent races if using_sysemu changes under us.*/
 	int local_using_sysemu;
@@ -325,13 +317,8 @@ void userspace(struct uml_pt_regs *regs)
 	/* Handle any immediate reschedules or signals */
 	interrupt_end();
 
-	if (getitimer(ITIMER_VIRTUAL, &timer))
-		printk(UM_KERN_ERR "Failed to get itimer, errno = %d\n", errno);
-	nsecs = timer.it_value.tv_sec * UM_NSEC_PER_SEC +
-		timer.it_value.tv_usec * UM_NSEC_PER_USEC;
-	nsecs += os_nsecs();
-
 	while (1) {
+
 		/*
 		 * This can legitimately fail if the process loads a
 		 * bogus value into a segment register.  It will
@@ -401,18 +388,7 @@ void userspace(struct uml_pt_regs *regs)
 			case SIGTRAP:
 				relay_signal(SIGTRAP, (struct siginfo *)&si, regs);
 				break;
-			case SIGVTALRM:
-				now = os_nsecs();
-				if (now < nsecs)
-					break;
-				block_signals();
-				(*sig_info[sig])(sig, (struct siginfo *)&si, regs);
-				unblock_signals();
-				nsecs = timer.it_value.tv_sec *
-					UM_NSEC_PER_SEC +
-					timer.it_value.tv_usec *
-					UM_NSEC_PER_USEC;
-				nsecs += os_nsecs();
+			case SIGALRM:
 				break;
 			case SIGIO:
 			case SIGILL:
@@ -460,7 +436,6 @@ __initcall(init_thread_regs);
 
 int copy_context_skas0(unsigned long new_stack, int pid)
 {
-	struct timeval tv = { .tv_sec = 0, .tv_usec = UM_USEC_PER_SEC / UM_HZ };
 	int err;
 	unsigned long current_stack = current_stub_stack();
 	struct stub_data *data = (struct stub_data *) current_stack;
@@ -472,11 +447,10 @@ int copy_context_skas0(unsigned long new_stack, int pid)
 	 * prepare offset and fd of child's stack as argument for parent's
 	 * and child's mmap2 calls
 	 */
-	*data = ((struct stub_data) { .offset	= MMAP_OFFSET(new_offset),
-				      .fd	= new_fd,
-				      .timer    = ((struct itimerval)
-					           { .it_value = tv,
-						     .it_interval = tv }) });
+	*data = ((struct stub_data) { 
+			.offset	= MMAP_OFFSET(new_offset),
+			.fd     = new_fd
+	});
 
 	err = ptrace_setregs(pid, thread_regs);
 	if (err < 0) {
diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c
index e9824d5..0e2bb7d 100644
--- a/arch/um/os-Linux/time.c
+++ b/arch/um/os-Linux/time.c
@@ -1,4 +1,5 @@
 /*
+ * Copyright (C) 2012-2014 Cisco Systems
  * Copyright (C) 2000 - 2007 Jeff Dike (jdike{addtoit,linux.intel}.com)
  * Licensed under the GPL
  */
@@ -10,177 +11,172 @@
 #include <sys/time.h>
 #include <kern_util.h>
 #include <os.h>
-#include "internal.h"
+#include <string.h>
+#include <timer-internal.h>
 
-int set_interval(void)
-{
-	int usec = UM_USEC_PER_SEC / UM_HZ;
-	struct itimerval interval = ((struct itimerval) { { 0, usec },
-							  { 0, usec } });
-
-	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
-		return -errno;
+static timer_t event_high_res_timer = 0;
 
-	return 0;
+static inline long long timeval_to_ns(const struct timeval *tv)
+{
+	return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
+		tv->tv_usec * UM_NSEC_PER_USEC;
 }
 
-int timer_one_shot(int ticks)
+static inline long long timespec_to_ns(const struct timespec *ts)
 {
-	unsigned long usec = ticks * UM_USEC_PER_SEC / UM_HZ;
-	unsigned long sec = usec / UM_USEC_PER_SEC;
-	struct itimerval interval;
-
-	usec %= UM_USEC_PER_SEC;
-	interval = ((struct itimerval) { { 0, 0 }, { sec, usec } });
+	return ((long long) ts->tv_sec * UM_NSEC_PER_SEC) +
+		ts->tv_nsec;
+}
 
-	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
-		return -errno;
+long long os_persistent_clock_emulation (void) {
+	struct timespec realtime_tp;
 
-	return 0;
+	clock_gettime(CLOCK_REALTIME, &realtime_tp);
+	return timespec_to_ns(&realtime_tp);
 }
 
 /**
- * timeval_to_ns - Convert timeval to nanoseconds
- * @ts:		pointer to the timeval variable to be converted
- *
- * Returns the scalar nanosecond representation of the timeval
- * parameter.
- *
- * Ripped from linux/time.h because it's a kernel header, and thus
- * unusable from here.
+ * os_timer_create() - create an new posix (interval) timer
  */
-static inline long long timeval_to_ns(const struct timeval *tv)
-{
-	return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
-		tv->tv_usec * UM_NSEC_PER_USEC;
+int os_timer_create(void* timer) {
+
+	timer_t* t = timer;
+
+	if(t == NULL) {
+		t = &event_high_res_timer;
+	}
+
+	if (timer_create(
+		CLOCK_MONOTONIC,
+		NULL,
+		t) == -1) {
+		return -1;
+	}
+	return 0;
 }
 
-long long disable_timer(void)
+int os_timer_set_interval(void* timer, void* i)
 {
-	struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } });
-	long long remain, max = UM_NSEC_PER_SEC / UM_HZ;
+	struct itimerspec its;
+	unsigned long long nsec;
+	timer_t* t = timer;
+	struct itimerspec* its_in = i;
 
-	if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0)
-		printk(UM_KERN_ERR "disable_timer - setitimer failed, "
-		       "errno = %d\n", errno);
+	if(t == NULL) {
+		t = &event_high_res_timer;
+	}
 
-	remain = timeval_to_ns(&time.it_value);
-	if (remain > max)
-		remain = max;
+	nsec = UM_NSEC_PER_SEC / UM_HZ;
 
-	return remain;
-}
+	if(its_in != NULL) {
+		its.it_value.tv_sec = its_in->it_value.tv_sec;
+		its.it_value.tv_nsec = its_in->it_value.tv_nsec;
+	} else {
+		its.it_value.tv_sec = 0;
+		its.it_value.tv_nsec = nsec;
+	}
 
-long long os_nsecs(void)
-{
-	struct timeval tv;
+	its.it_interval.tv_sec = 0;
+	its.it_interval.tv_nsec = nsec;
 
-	gettimeofday(&tv, NULL);
-	return timeval_to_ns(&tv);
-}
+	if(timer_settime(*t, 0, &its, NULL) == -1) {
+		return -errno;
+	}
 
-#ifdef UML_CONFIG_NO_HZ_COMMON
-static int after_sleep_interval(struct timespec *ts)
-{
 	return 0;
 }
 
-static void deliver_alarm(void)
+/**
+ * os_timer_remain() - returns the remaining nano seconds of the given interval
+ *                     timer
+ * Because this is the remaining time of an interval timer, which correspondends
+ * to HZ, this value can never be bigger than one second. Just
+ * the nanosecond part of the timer is returned.
+ * The returned time is relative to the start time of the interval timer.
+ * Return an negative value in an error case.
+ */
+long os_timer_remain(void* timer)
 {
-	alarm_handler(SIGVTALRM, NULL, NULL);
-}
+	struct itimerspec its;
+	timer_t* t = timer;
 
-static unsigned long long sleep_time(unsigned long long nsecs)
-{
-	return nsecs;
-}
+	if(t == NULL) {
+		t = &event_high_res_timer;
+	}
 
-#else
-unsigned long long last_tick;
-unsigned long long skew;
+	if(timer_gettime(t, &its) == -1) {
+		return -errno;
+	}
+
+	return its.it_value.tv_nsec;
+}
 
-static void deliver_alarm(void)
+int os_timer_one_shot(int ticks)
 {
-	unsigned long long this_tick = os_nsecs();
-	int one_tick = UM_NSEC_PER_SEC / UM_HZ;
+	struct itimerspec its;
+	unsigned long long nsec;
+	unsigned long sec;
 
-	/* Protection against the host's time going backwards */
-	if ((last_tick != 0) && (this_tick < last_tick))
-		this_tick = last_tick;
+    nsec = (ticks + 1);
+    sec = nsec / UM_NSEC_PER_SEC;
+	nsec = nsec % UM_NSEC_PER_SEC;
 
-	if (last_tick == 0)
-		last_tick = this_tick - one_tick;
+	its.it_value.tv_sec = nsec / UM_NSEC_PER_SEC;
+	its.it_value.tv_nsec = nsec;
 
-	skew += this_tick - last_tick;
+	its.it_interval.tv_sec = 0;
+	its.it_interval.tv_nsec = 0; // we cheat here
 
-	while (skew >= one_tick) {
-		alarm_handler(SIGVTALRM, NULL, NULL);
-		skew -= one_tick;
-	}
-
-	last_tick = this_tick;
+	timer_settime(event_high_res_timer, 0, &its, NULL);
+	return 0;
 }
 
-static unsigned long long sleep_time(unsigned long long nsecs)
+/**
+ * os_timer_disable() - disable the posix (interval) timer
+ * Returns the remaining interval timer time in nanoseconds
+ */
+long long os_timer_disable(void)
 {
-	return nsecs > skew ? nsecs - skew : 0;
+	struct itimerspec its;
+
+	memset(&its, 0, sizeof(struct itimerspec));
+	timer_settime(event_high_res_timer, 0, &its, &its);
+
+	return its.it_value.tv_sec * UM_NSEC_PER_SEC + its.it_value.tv_nsec;
 }
 
-static inline long long timespec_to_us(const struct timespec *ts)
+long long os_vnsecs(void)
 {
-	return ((long long) ts->tv_sec * UM_USEC_PER_SEC) +
-		ts->tv_nsec / UM_NSEC_PER_USEC;
+	struct timespec ts;
+
+	clock_gettime(CLOCK_PROCESS_CPUTIME_ID,&ts);
+	return timespec_to_ns(&ts);
 }
 
-static int after_sleep_interval(struct timespec *ts)
+long long os_nsecs(void)
 {
-	int usec = UM_USEC_PER_SEC / UM_HZ;
-	long long start_usecs = timespec_to_us(ts);
-	struct timeval tv;
-	struct itimerval interval;
-
-	/*
-	 * It seems that rounding can increase the value returned from
-	 * setitimer to larger than the one passed in.  Over time,
-	 * this will cause the remaining time to be greater than the
-	 * tick interval.  If this happens, then just reduce the first
-	 * tick to the interval value.
-	 */
-	if (start_usecs > usec)
-		start_usecs = usec;
-
-	start_usecs -= skew / UM_NSEC_PER_USEC;
-	if (start_usecs < 0)
-		start_usecs = 0;
-
-	tv = ((struct timeval) { .tv_sec  = start_usecs / UM_USEC_PER_SEC,
-				 .tv_usec = start_usecs % UM_USEC_PER_SEC });
-	interval = ((struct itimerval) { { 0, usec }, tv });
-
-	if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
-		return -errno;
+	struct timespec ts;
 
-	return 0;
+	clock_gettime(CLOCK_MONOTONIC,&ts);
+	return timespec_to_ns(&ts);
 }
-#endif
 
-void idle_sleep(unsigned long long nsecs)
+/**
+ * os_idle_sleep() - sleep for a given time of nsecs
+ * @nsecs: nanoseconds to sleep
+ */
+void os_idle_sleep(unsigned long long nsecs)
 {
 	struct timespec ts;
 
-	/*
-	 * nsecs can come in as zero, in which case, this starts a
-	 * busy loop.  To prevent this, reset nsecs to the tick
-	 * interval if it is zero.
-	 */
-	if (nsecs == 0)
-		nsecs = UM_NSEC_PER_SEC / UM_HZ;
-
-	nsecs = sleep_time(nsecs);
-	ts = ((struct timespec) { .tv_sec	= nsecs / UM_NSEC_PER_SEC,
-				  .tv_nsec	= nsecs % UM_NSEC_PER_SEC });
-
-	if (nanosleep(&ts, &ts) == 0)
-		deliver_alarm();
-	after_sleep_interval(&ts);
+	if (nsecs <= 0) {
+		return;
+	}
+
+	ts = ((struct timespec) {
+			.tv_sec  = nsecs / UM_NSEC_PER_SEC,
+			.tv_nsec = nsecs % UM_NSEC_PER_SEC
+	});
+
+	clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, NULL);
 }
-- 
2.4.3

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