[for-next][PATCH 0/7] tracing: Updates for 4.9

[for-next][PATCH 0/7] tracing: Updates for 4.9

[Steven Rostedt]

  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
for-next

Head SHA1: 7b2c86250122de316cbab8754050622ead04af39


Dmitry Safonov (1):
      tracing/uprobe: Drop isdigit() check in create_trace_uprobe

Jon Masters (1):
      tracing: Add documentation for hwlat_detector tracer

Namhyung Kim (2):
      function_graph: Handle TRACE_BPUTS in print_graph_comment
      ftrace: Access ret_stack->subtime only in the function profiler

Steven Rostedt (Red Hat) (3):
      tracing: Added hardware latency tracer
      tracing: Have hwlat trace migrate across tracing_cpumask CPUs
      tracing: Add NMI tracing in hwlat detector

----
 Documentation/trace/ftrace.txt         |  10 +-
 Documentation/trace/hwlat_detector.txt |  79 ++++
 arch/sh/kernel/ftrace.c                |   4 +-
 include/linux/ftrace.h                 |   2 +
 include/linux/ftrace_irq.h             |  31 +-
 kernel/trace/Kconfig                   |  35 ++
 kernel/trace/Makefile                  |   1 +
 kernel/trace/ftrace.c                  |   6 +
 kernel/trace/trace.c                   |   2 +-
 kernel/trace/trace.h                   |   3 +
 kernel/trace/trace_entries.h           |  27 ++
 kernel/trace/trace_functions_graph.c   |   6 +-
 kernel/trace/trace_hwlat.c             | 633 +++++++++++++++++++++++++++++++++
 kernel/trace/trace_output.c            |  66 ++++
 kernel/trace/trace_uprobe.c            |   4 -
 15 files changed, 892 insertions(+), 17 deletions(-)
 create mode 100644 Documentation/trace/hwlat_detector.txt
 create mode 100644 kernel/trace/trace_hwlat.c

[for-next][PATCH 1/7] tracing/uprobe: Drop isdigit() check in create_trace_uprobe

[Steven Rostedt]

[-- Attachment #1: 0001-tracing-uprobe-Drop-isdigit-check-in-create_trace_up.patch --]
[-- Type: text/plain, Size: 1292 bytes --]

From: Dmitry Safonov <dsafonov@virtuozzo.com>

It's useless. Before:
  [tracing]# echo 'p:test /a:0x0' >> uprobe_events
  [tracing]# echo 'p:test a:0x0' >> uprobe_events
  -bash: echo: write error: No such file or directory
  [tracing]# echo 'p:test 1:0x0' >> uprobe_events
  -bash: echo: write error: Invalid argument

After:
  [tracing]# echo 'p:test 1:0x0' >> uprobe_events
  -bash: echo: write error: No such file or directory

Link: http://lkml.kernel.org/r/20160825152110.25663-3-dsafonov@virtuozzo.com

Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace_uprobe.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index c53485441c88..a74f2d9ff379 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -427,10 +427,6 @@ static int create_trace_uprobe(int argc, char **argv)
 		pr_info("Probe point is not specified.\n");
 		return -EINVAL;
 	}
-	if (isdigit(argv[1][0])) {
-		pr_info("probe point must be have a filename.\n");
-		return -EINVAL;
-	}
 	arg = strchr(argv[1], ':');
 	if (!arg) {
 		ret = -EINVAL;
-- 
2.8.1

[for-next][PATCH 2/7] function_graph: Handle TRACE_BPUTS in print_graph_comment

[Steven Rostedt]

[-- Attachment #1: 0002-function_graph-Handle-TRACE_BPUTS-in-print_graph_com.patch --]
[-- Type: text/plain, Size: 2903 bytes --]

From: Namhyung Kim <namhyung@kernel.org>

It missed to handle TRACE_BPUTS so messages recorded by trace_bputs()
will be shown with symbol info unnecessarily.

You can see it with the trace_printk sample code:

  # cd /sys/kernel/tracing/
  # echo sys_sync > set_graph_function
  # echo 1 > options/sym-offset
  # echo function_graph > current_tracer

Note that the sys_sync filter was there to prevent recording other
functions and the sym-offset option was needed since the first message
was called from a module init function so kallsyms doesn't have the
symbol and omitted in the output.

  # cd ~/build/kernel
  # insmod samples/trace_printk/trace-printk.ko

  # cd -
  # head trace

Before:

  # tracer: function_graph
  #
  # CPU  DURATION                  FUNCTION CALLS
  # |     |   |                     |   |   |   |
   1)               |  /* 0xffffffffa0002000: This is a static string that will use trace_bputs */
   1)               |  /* This is a dynamic string that will use trace_puts */
   1)               |  /* trace_printk_irq_work+0x5/0x7b [trace_printk]: (irq) This is a static string that will use trace_bputs */
   1)               |  /* (irq) This is a dynamic string that will use trace_puts */
   1)               |  /* (irq) This is a static string that will use trace_bprintk() */
   1)               |  /* (irq) This is a dynamic string that will use trace_printk */

After:

  # tracer: function_graph
  #
  # CPU  DURATION                  FUNCTION CALLS
  # |     |   |                     |   |   |   |
   1)               |  /* This is a static string that will use trace_bputs */
   1)               |  /* This is a dynamic string that will use trace_puts */
   1)               |  /* (irq) This is a static string that will use trace_bputs */
   1)               |  /* (irq) This is a dynamic string that will use trace_puts */
   1)               |  /* (irq) This is a static string that will use trace_bprintk() */
   1)               |  /* (irq) This is a dynamic string that will use trace_printk */

Link: http://lkml.kernel.org/r/20160901024354.13720-1-namhyung@kernel.org

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace_functions_graph.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 7363ccf79512..e14017c36170 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -1120,6 +1120,11 @@ print_graph_comment(struct trace_seq *s, struct trace_entry *ent,
 	trace_seq_puts(s, "/* ");
 
 	switch (iter->ent->type) {
+	case TRACE_BPUTS:
+		ret = trace_print_bputs_msg_only(iter);
+		if (ret != TRACE_TYPE_HANDLED)
+			return ret;
+		break;
 	case TRACE_BPRINT:
 		ret = trace_print_bprintk_msg_only(iter);
 		if (ret != TRACE_TYPE_HANDLED)
-- 
2.8.1

[for-next][PATCH 3/7] ftrace: Access ret_stack->subtime only in the function profiler

[Steven Rostedt]

[-- Attachment #1: 0003-ftrace-Access-ret_stack-subtime-only-in-the-function.patch --]
[-- Type: text/plain, Size: 3426 bytes --]

From: Namhyung Kim <namhyung@kernel.org>

The subtime is used only for function profiler with function graph
tracer enabled.  Move the definition of subtime under
CONFIG_FUNCTION_PROFILER to reduce the memory usage.  Also move the
initialization of subtime into the graph entry callback.

Link: http://lkml.kernel.org/r/20160831025529.24018-1-namhyung@kernel.org

Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 Documentation/trace/ftrace.txt       | 10 +++++-----
 include/linux/ftrace.h               |  2 ++
 kernel/trace/ftrace.c                |  6 ++++++
 kernel/trace/trace_functions_graph.c |  1 -
 4 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index a6b3705e62a6..185c39fea2a0 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -858,11 +858,11 @@ x494] <- /root/a.out[+0x4a8] <- /lib/libc-2.7.so[+0x1e1a6]
 	       When enabled, it will account time the task has been
 	       scheduled out as part of the function call.
 
-  graph-time - When running function graph tracer, to include the
-  	       time to call nested functions. When this is not set,
-	       the time reported for the function will only include
-	       the time the function itself executed for, not the time
-	       for functions that it called.
+  graph-time - When running function profiler with function graph tracer,
+	       to include the time to call nested functions. When this is
+	       not set, the time reported for the function will only
+	       include the time the function itself executed for, not the
+	       time for functions that it called.
 
   record-cmd - When any event or tracer is enabled, a hook is enabled
   	       in the sched_switch trace point to fill comm cache
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 7d565afe35d2..1e2b316d6693 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -794,7 +794,9 @@ struct ftrace_ret_stack {
 	unsigned long ret;
 	unsigned long func;
 	unsigned long long calltime;
+#ifdef CONFIG_FUNCTION_PROFILER
 	unsigned long long subtime;
+#endif
 	unsigned long fp;
 };
 
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 84752c8e28b5..2050a7652a86 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -872,7 +872,13 @@ function_profile_call(unsigned long ip, unsigned long parent_ip,
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 static int profile_graph_entry(struct ftrace_graph_ent *trace)
 {
+	int index = trace->depth;
+
 	function_profile_call(trace->func, 0, NULL, NULL);
+
+	if (index >= 0 && index < FTRACE_RETFUNC_DEPTH)
+		current->ret_stack[index].subtime = 0;
+
 	return 1;
 }
 
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index e14017c36170..148c90f1e49b 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -170,7 +170,6 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
 	current->ret_stack[index].ret = ret;
 	current->ret_stack[index].func = func;
 	current->ret_stack[index].calltime = calltime;
-	current->ret_stack[index].subtime = 0;
 	current->ret_stack[index].fp = frame_pointer;
 	*depth = current->curr_ret_stack;
 
-- 
2.8.1

[for-next][PATCH 4/7] tracing: Added hardware latency tracer

[Steven Rostedt]

[-- Attachment #1: 0004-tracing-Added-hardware-latency-tracer.patch --]
[-- Type: text/plain, Size: 23671 bytes --]

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

The hardware latency tracer has been in the PREEMPT_RT patch for some time.
It is used to detect possible SMIs or any other hardware interruptions that
the kernel is unaware of. Note, NMIs may also be detected, but that may be
good to note as well.

The logic is pretty simple. It simply creates a thread that spins on a
single CPU for a specified amount of time (width) within a periodic window
(window). These numbers may be adjusted by their cooresponding names in

   /sys/kernel/tracing/hwlat_detector/

The defaults are window = 1000000 us (1 second)
                 width  =  500000 us (1/2 second)

The loop consists of:

	t1 = trace_clock_local();
	t2 = trace_clock_local();

Where trace_clock_local() is a variant of sched_clock().

The difference of t2 - t1 is recorded as the "inner" timestamp and also the
timestamp  t1 - prev_t2 is recorded as the "outer" timestamp. If either of
these differences are greater than the time denoted in
/sys/kernel/tracing/tracing_thresh then it records the event.

When this tracer is started, and tracing_thresh is zero, it changes to the
default threshold of 10 us.

The hwlat tracer in the PREEMPT_RT patch was originally written by
Jon Masters. I have modified it quite a bit and turned it into a
tracer.

Based-on-code-by: Jon Masters <jcm@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/Kconfig         |  35 +++
 kernel/trace/Makefile        |   1 +
 kernel/trace/trace.c         |   2 +-
 kernel/trace/trace.h         |   3 +
 kernel/trace/trace_entries.h |  23 ++
 kernel/trace/trace_hwlat.c   | 527 +++++++++++++++++++++++++++++++++++++++++++
 kernel/trace/trace_output.c  |  52 +++++
 7 files changed, 642 insertions(+), 1 deletion(-)
 create mode 100644 kernel/trace/trace_hwlat.c

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index f4b86e8ca1e7..72c07c2ffd79 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -221,6 +221,41 @@ config SCHED_TRACER
 	  This tracer tracks the latency of the highest priority task
 	  to be scheduled in, starting from the point it has woken up.
 
+config HWLAT_TRACER
+	bool "Tracer to detect hardware latencies (like SMIs)"
+	select GENERIC_TRACER
+	help
+	 This tracer, when enabled will create one or more kernel threads,
+	 depening on what the cpumask file is set to, which each thread
+	 spinning in a loop looking for interruptions caused by
+	 something other than the kernel. For example, if a
+	 System Management Interrupt (SMI) takes a noticeable amount of
+	 time, this tracer will detect it. This is useful for testing
+	 if a system is reliable for Real Time tasks.
+
+	 Some files are created in the tracing directory when this
+	 is enabled:
+
+	   hwlat_detector/width   - time in usecs for how long to spin for
+	   hwlat_detector/window  - time in usecs between the start of each
+				     iteration
+
+	 A kernel thread is created that will spin with interrupts disabled
+	 for "width" microseconds in every "widow" cycle. It will not spin
+	 for "window - width" microseconds, where the system can
+	 continue to operate.
+
+	 The output will appear in the trace and trace_pipe files.
+
+	 When the tracer is not running, it has no affect on the system,
+	 but when it is running, it can cause the system to be
+	 periodically non responsive. Do not run this tracer on a
+	 production system.
+
+	 To enable this tracer, echo in "hwlat" into the current_tracer
+	 file. Every time a latency is greater than tracing_thresh, it will
+	 be recorded into the ring buffer.
+
 config ENABLE_DEFAULT_TRACERS
 	bool "Trace process context switches and events"
 	depends on !GENERIC_TRACER
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index d0a1617b52b4..992ab9d99f35 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -41,6 +41,7 @@ obj-$(CONFIG_FUNCTION_TRACER) += trace_functions.o
 obj-$(CONFIG_IRQSOFF_TRACER) += trace_irqsoff.o
 obj-$(CONFIG_PREEMPT_TRACER) += trace_irqsoff.o
 obj-$(CONFIG_SCHED_TRACER) += trace_sched_wakeup.o
+obj-$(CONFIG_HWLAT_TRACER) += trace_hwlat.o
 obj-$(CONFIG_NOP_TRACER) += trace_nop.o
 obj-$(CONFIG_STACK_TRACER) += trace_stack.o
 obj-$(CONFIG_MMIOTRACE) += trace_mmiotrace.o
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index dade4c9559cc..474cc814e16d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1047,7 +1047,7 @@ void disable_trace_on_warning(void)
  *
  * Shows real state of the ring buffer if it is enabled or not.
  */
-static int tracer_tracing_is_on(struct trace_array *tr)
+int tracer_tracing_is_on(struct trace_array *tr)
 {
 	if (tr->trace_buffer.buffer)
 		return ring_buffer_record_is_on(tr->trace_buffer.buffer);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index f783df416726..1d866b0c1567 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -38,6 +38,7 @@ enum trace_type {
 	TRACE_USER_STACK,
 	TRACE_BLK,
 	TRACE_BPUTS,
+	TRACE_HWLAT,
 
 	__TRACE_LAST_TYPE,
 };
@@ -326,6 +327,7 @@ extern void __ftrace_bad_type(void);
 		IF_ASSIGN(var, ent, struct print_entry, TRACE_PRINT);	\
 		IF_ASSIGN(var, ent, struct bprint_entry, TRACE_BPRINT);	\
 		IF_ASSIGN(var, ent, struct bputs_entry, TRACE_BPUTS);	\
+		IF_ASSIGN(var, ent, struct hwlat_entry, TRACE_HWLAT);	\
 		IF_ASSIGN(var, ent, struct trace_mmiotrace_rw,		\
 			  TRACE_MMIO_RW);				\
 		IF_ASSIGN(var, ent, struct trace_mmiotrace_map,		\
@@ -571,6 +573,7 @@ void tracing_reset_current(int cpu);
 void tracing_reset_all_online_cpus(void);
 int tracing_open_generic(struct inode *inode, struct file *filp);
 bool tracing_is_disabled(void);
+int tracer_tracing_is_on(struct trace_array *tr);
 struct dentry *trace_create_file(const char *name,
 				 umode_t mode,
 				 struct dentry *parent,
diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
index 5c30efcda5e6..70d47dd99359 100644
--- a/kernel/trace/trace_entries.h
+++ b/kernel/trace/trace_entries.h
@@ -322,3 +322,26 @@ FTRACE_ENTRY(branch, trace_branch,
 	FILTER_OTHER
 );
 
+
+FTRACE_ENTRY(hwlat, hwlat_entry,
+
+	TRACE_HWLAT,
+
+	F_STRUCT(
+		__field(	u64,			duration	)
+		__field(	u64,			outer_duration	)
+		__field_struct( struct timespec,	timestamp	)
+		__field_desc(	long,	timestamp,	tv_sec		)
+		__field_desc(	long,	timestamp,	tv_nsec		)
+		__field(	unsigned int,		seqnum		)
+	),
+
+	F_printk("cnt:%u\tts:%010lu.%010lu\tinner:%llu\touter:%llu\n",
+		 __entry->seqnum,
+		 __entry->tv_sec,
+		 __entry->tv_nsec,
+		 __entry->duration,
+		 __entry->outer_duration),
+
+	FILTER_OTHER
+);
diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
new file mode 100644
index 000000000000..08dfabe4e862
--- /dev/null
+++ b/kernel/trace/trace_hwlat.c
@@ -0,0 +1,527 @@
+/*
+ * trace_hwlatdetect.c - A simple Hardware Latency detector.
+ *
+ * Use this tracer to detect large system latencies induced by the behavior of
+ * certain underlying system hardware or firmware, independent of Linux itself.
+ * The code was developed originally to detect the presence of SMIs on Intel
+ * and AMD systems, although there is no dependency upon x86 herein.
+ *
+ * The classical example usage of this tracer is in detecting the presence of
+ * SMIs or System Management Interrupts on Intel and AMD systems. An SMI is a
+ * somewhat special form of hardware interrupt spawned from earlier CPU debug
+ * modes in which the (BIOS/EFI/etc.) firmware arranges for the South Bridge
+ * LPC (or other device) to generate a special interrupt under certain
+ * circumstances, for example, upon expiration of a special SMI timer device,
+ * due to certain external thermal readings, on certain I/O address accesses,
+ * and other situations. An SMI hits a special CPU pin, triggers a special
+ * SMI mode (complete with special memory map), and the OS is unaware.
+ *
+ * Although certain hardware-inducing latencies are necessary (for example,
+ * a modern system often requires an SMI handler for correct thermal control
+ * and remote management) they can wreak havoc upon any OS-level performance
+ * guarantees toward low-latency, especially when the OS is not even made
+ * aware of the presence of these interrupts. For this reason, we need a
+ * somewhat brute force mechanism to detect these interrupts. In this case,
+ * we do it by hogging all of the CPU(s) for configurable timer intervals,
+ * sampling the built-in CPU timer, looking for discontiguous readings.
+ *
+ * WARNING: This implementation necessarily introduces latencies. Therefore,
+ *          you should NEVER use this tracer while running in a production
+ *          environment requiring any kind of low-latency performance
+ *          guarantee(s).
+ *
+ * Copyright (C) 2008-2009 Jon Masters, Red Hat, Inc. <jcm@redhat.com>
+ * Copyright (C) 2013-2016 Steven Rostedt, Red Hat, Inc. <srostedt@redhat.com>
+ *
+ * Includes useful feedback from Clark Williams <clark@redhat.com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+#include <linux/kthread.h>
+#include <linux/tracefs.h>
+#include <linux/uaccess.h>
+#include <linux/delay.h>
+#include "trace.h"
+
+static struct trace_array	*hwlat_trace;
+
+#define U64STR_SIZE		22			/* 20 digits max */
+
+#define BANNER			"hwlat_detector: "
+#define DEFAULT_SAMPLE_WINDOW	1000000			/* 1s */
+#define DEFAULT_SAMPLE_WIDTH	500000			/* 0.5s */
+#define DEFAULT_LAT_THRESHOLD	10			/* 10us */
+
+/* sampling thread*/
+static struct task_struct *hwlat_kthread;
+
+static struct dentry *hwlat_sample_width;	/* sample width us */
+static struct dentry *hwlat_sample_window;	/* sample window us */
+
+/* Save the previous tracing_thresh value */
+static unsigned long save_tracing_thresh;
+
+/* If the user changed threshold, remember it */
+static u64 last_tracing_thresh = DEFAULT_LAT_THRESHOLD * NSEC_PER_USEC;
+
+/* Individual latency samples are stored here when detected. */
+struct hwlat_sample {
+	u64		seqnum;		/* unique sequence */
+	u64		duration;	/* delta */
+	u64		outer_duration;	/* delta (outer loop) */
+	struct timespec	timestamp;	/* wall time */
+};
+
+/* keep the global state somewhere. */
+static struct hwlat_data {
+
+	struct mutex lock;		/* protect changes */
+
+	u64	count;			/* total since reset */
+
+	u64	sample_window;		/* total sampling window (on+off) */
+	u64	sample_width;		/* active sampling portion of window */
+
+} hwlat_data = {
+	.sample_window		= DEFAULT_SAMPLE_WINDOW,
+	.sample_width		= DEFAULT_SAMPLE_WIDTH,
+};
+
+static void trace_hwlat_sample(struct hwlat_sample *sample)
+{
+	struct trace_array *tr = hwlat_trace;
+	struct trace_event_call *call = &event_hwlat;
+	struct ring_buffer *buffer = tr->trace_buffer.buffer;
+	struct ring_buffer_event *event;
+	struct hwlat_entry *entry;
+	unsigned long flags;
+	int pc;
+
+	pc = preempt_count();
+	local_save_flags(flags);
+
+	event = trace_buffer_lock_reserve(buffer, TRACE_HWLAT, sizeof(*entry),
+					  flags, pc);
+	if (!event)
+		return;
+	entry	= ring_buffer_event_data(event);
+	entry->seqnum			= sample->seqnum;
+	entry->duration			= sample->duration;
+	entry->outer_duration		= sample->outer_duration;
+	entry->timestamp		= sample->timestamp;
+
+	if (!call_filter_check_discard(call, entry, buffer, event))
+		__buffer_unlock_commit(buffer, event);
+}
+
+/* Macros to encapsulate the time capturing infrastructure */
+#define time_type	u64
+#define time_get()	trace_clock_local()
+#define time_to_us(x)	div_u64(x, 1000)
+#define time_sub(a, b)	((a) - (b))
+#define init_time(a, b)	(a = b)
+#define time_u64(a)	a
+
+/**
+ * get_sample - sample the CPU TSC and look for likely hardware latencies
+ *
+ * Used to repeatedly capture the CPU TSC (or similar), looking for potential
+ * hardware-induced latency. Called with interrupts disabled and with
+ * hwlat_data.lock held.
+ */
+static int get_sample(void)
+{
+	struct trace_array *tr = hwlat_trace;
+	time_type start, t1, t2, last_t2;
+	s64 diff, total, last_total = 0;
+	u64 sample = 0;
+	u64 thresh = tracing_thresh;
+	u64 outer_sample = 0;
+	int ret = -1;
+
+	do_div(thresh, NSEC_PER_USEC); /* modifies interval value */
+
+	init_time(last_t2, 0);
+	start = time_get(); /* start timestamp */
+
+	do {
+
+		t1 = time_get();	/* we'll look for a discontinuity */
+		t2 = time_get();
+
+		if (time_u64(last_t2)) {
+			/* Check the delta from outer loop (t2 to next t1) */
+			diff = time_to_us(time_sub(t1, last_t2));
+			/* This shouldn't happen */
+			if (diff < 0) {
+				pr_err(BANNER "time running backwards\n");
+				goto out;
+			}
+			if (diff > outer_sample)
+				outer_sample = diff;
+		}
+		last_t2 = t2;
+
+		total = time_to_us(time_sub(t2, start)); /* sample width */
+
+		/* Check for possible overflows */
+		if (total < last_total) {
+			pr_err("Time total overflowed\n");
+			break;
+		}
+		last_total = total;
+
+		/* This checks the inner loop (t1 to t2) */
+		diff = time_to_us(time_sub(t2, t1));     /* current diff */
+
+		/* This shouldn't happen */
+		if (diff < 0) {
+			pr_err(BANNER "time running backwards\n");
+			goto out;
+		}
+
+		if (diff > sample)
+			sample = diff; /* only want highest value */
+
+	} while (total <= hwlat_data.sample_width);
+
+	ret = 0;
+
+	/* If we exceed the threshold value, we have found a hardware latency */
+	if (sample > thresh || outer_sample > thresh) {
+		struct hwlat_sample s;
+
+		ret = 1;
+
+		hwlat_data.count++;
+		s.seqnum = hwlat_data.count;
+		s.duration = sample;
+		s.outer_duration = outer_sample;
+		s.timestamp = CURRENT_TIME;
+		trace_hwlat_sample(&s);
+
+		/* Keep a running maximum ever recorded hardware latency */
+		if (sample > tr->max_latency)
+			tr->max_latency = sample;
+	}
+
+out:
+	return ret;
+}
+
+/*
+ * kthread_fn - The CPU time sampling/hardware latency detection kernel thread
+ *
+ * Used to periodically sample the CPU TSC via a call to get_sample. We
+ * disable interrupts, which does (intentionally) introduce latency since we
+ * need to ensure nothing else might be running (and thus preempting).
+ * Obviously this should never be used in production environments.
+ *
+ * Currently this runs on which ever CPU it was scheduled on, but most
+ * real-world hardware latency situations occur across several CPUs,
+ * but we might later generalize this if we find there are any actualy
+ * systems with alternate SMI delivery or other hardware latencies.
+ */
+static int kthread_fn(void *data)
+{
+	u64 interval;
+
+	while (!kthread_should_stop()) {
+
+		local_irq_disable();
+		get_sample();
+		local_irq_enable();
+
+		mutex_lock(&hwlat_data.lock);
+		interval = hwlat_data.sample_window - hwlat_data.sample_width;
+		mutex_unlock(&hwlat_data.lock);
+
+		do_div(interval, USEC_PER_MSEC); /* modifies interval value */
+
+		/* Always sleep for at least 1ms */
+		if (interval < 1)
+			interval = 1;
+
+		if (msleep_interruptible(interval))
+			break;
+	}
+
+	return 0;
+}
+
+/**
+ * start_kthread - Kick off the hardware latency sampling/detector kthread
+ *
+ * This starts the kernel thread that will sit and sample the CPU timestamp
+ * counter (TSC or similar) and look for potential hardware latencies.
+ */
+static int start_kthread(struct trace_array *tr)
+{
+	struct task_struct *kthread;
+
+	kthread = kthread_create(kthread_fn, NULL, "hwlatd");
+	if (IS_ERR(kthread)) {
+		pr_err(BANNER "could not start sampling thread\n");
+		return -ENOMEM;
+	}
+	hwlat_kthread = kthread;
+	wake_up_process(kthread);
+
+	return 0;
+}
+
+/**
+ * stop_kthread - Inform the hardware latency samping/detector kthread to stop
+ *
+ * This kicks the running hardware latency sampling/detector kernel thread and
+ * tells it to stop sampling now. Use this on unload and at system shutdown.
+ */
+static void stop_kthread(void)
+{
+	if (!hwlat_kthread)
+		return;
+	kthread_stop(hwlat_kthread);
+	hwlat_kthread = NULL;
+}
+
+/*
+ * hwlat_read - Wrapper read function for reading both window and width
+ * @filp: The active open file structure
+ * @ubuf: The userspace provided buffer to read value into
+ * @cnt: The maximum number of bytes to read
+ * @ppos: The current "file" position
+ *
+ * This function provides a generic read implementation for the global state
+ * "hwlat_data" structure filesystem entries.
+ */
+static ssize_t hwlat_read(struct file *filp, char __user *ubuf,
+			  size_t cnt, loff_t *ppos)
+{
+	char buf[U64STR_SIZE];
+	u64 *entry = filp->private_data;
+	u64 val;
+	int len;
+
+	if (!entry)
+		return -EFAULT;
+
+	if (cnt > sizeof(buf))
+		cnt = sizeof(buf);
+
+	val = *entry;
+
+	len = snprintf(buf, sizeof(buf), "%llu\n", val);
+
+	return simple_read_from_buffer(ubuf, cnt, ppos, buf, len);
+}
+
+/**
+ * hwlat_width_write - Write function for "width" entry
+ * @filp: The active open file structure
+ * @ubuf: The user buffer that contains the value to write
+ * @cnt: The maximum number of bytes to write to "file"
+ * @ppos: The current position in @file
+ *
+ * This function provides a write implementation for the "width" interface
+ * to the hardware latency detector. It can be used to configure
+ * for how many us of the total window us we will actively sample for any
+ * hardware-induced latency periods. Obviously, it is not possible to
+ * sample constantly and have the system respond to a sample reader, or,
+ * worse, without having the system appear to have gone out to lunch. It
+ * is enforced that width is less that the total window size.
+ */
+static ssize_t
+hwlat_width_write(struct file *filp, const char __user *ubuf,
+		  size_t cnt, loff_t *ppos)
+{
+	u64 val;
+	int err;
+
+	err = kstrtoull_from_user(ubuf, cnt, 10, &val);
+	if (err)
+		return err;
+
+	mutex_lock(&hwlat_data.lock);
+	if (val < hwlat_data.sample_window)
+		hwlat_data.sample_width = val;
+	else
+		err = -EINVAL;
+	mutex_unlock(&hwlat_data.lock);
+
+	if (err)
+		return err;
+
+	return cnt;
+}
+
+/**
+ * hwlat_window_write - Write function for "window" entry
+ * @filp: The active open file structure
+ * @ubuf: The user buffer that contains the value to write
+ * @cnt: The maximum number of bytes to write to "file"
+ * @ppos: The current position in @file
+ *
+ * This function provides a write implementation for the "window" interface
+ * to the hardware latency detetector. The window is the total time
+ * in us that will be considered one sample period. Conceptually, windows
+ * occur back-to-back and contain a sample width period during which
+ * actual sampling occurs. Can be used to write a new total window size. It
+ * is enfoced that any value written must be greater than the sample width
+ * size, or an error results.
+ */
+static ssize_t
+hwlat_window_write(struct file *filp, const char __user *ubuf,
+		   size_t cnt, loff_t *ppos)
+{
+	u64 val;
+	int err;
+
+	err = kstrtoull_from_user(ubuf, cnt, 10, &val);
+	if (err)
+		return err;
+
+	mutex_lock(&hwlat_data.lock);
+	if (hwlat_data.sample_width < val)
+		hwlat_data.sample_window = val;
+	else
+		err = -EINVAL;
+	mutex_unlock(&hwlat_data.lock);
+
+	if (err)
+		return err;
+
+	return cnt;
+}
+
+static const struct file_operations width_fops = {
+	.open		= tracing_open_generic,
+	.read		= hwlat_read,
+	.write		= hwlat_width_write,
+};
+
+static const struct file_operations window_fops = {
+	.open		= tracing_open_generic,
+	.read		= hwlat_read,
+	.write		= hwlat_window_write,
+};
+
+/**
+ * init_tracefs - A function to initialize the tracefs interface files
+ *
+ * This function creates entries in tracefs for "hwlat_detector".
+ * It creates the hwlat_detector directory in the tracing directory,
+ * and within that directory is the count, width and window files to
+ * change and view those values.
+ */
+static int init_tracefs(void)
+{
+	struct dentry *d_tracer;
+	struct dentry *top_dir;
+
+	d_tracer = tracing_init_dentry();
+	if (IS_ERR(d_tracer))
+		return -ENOMEM;
+
+	top_dir = tracefs_create_dir("hwlat_detector", d_tracer);
+	if (!top_dir)
+		return -ENOMEM;
+
+	hwlat_sample_window = tracefs_create_file("window", 0640,
+						  top_dir,
+						  &hwlat_data.sample_window,
+						  &window_fops);
+	if (!hwlat_sample_window)
+		goto err;
+
+	hwlat_sample_width = tracefs_create_file("width", 0644,
+						 top_dir,
+						 &hwlat_data.sample_width,
+						 &width_fops);
+	if (!hwlat_sample_width)
+		goto err;
+
+	return 0;
+
+ err:
+	tracefs_remove_recursive(top_dir);
+	return -ENOMEM;
+}
+
+static void hwlat_tracer_start(struct trace_array *tr)
+{
+	int err;
+
+	err = start_kthread(tr);
+	if (err)
+		pr_err(BANNER "Cannot start hwlat kthread\n");
+}
+
+static void hwlat_tracer_stop(struct trace_array *tr)
+{
+	stop_kthread();
+}
+
+static bool hwlat_busy;
+
+static int hwlat_tracer_init(struct trace_array *tr)
+{
+	/* Only allow one instance to enable this */
+	if (hwlat_busy)
+		return -EBUSY;
+
+	hwlat_trace = tr;
+
+	hwlat_data.count = 0;
+	tr->max_latency = 0;
+	save_tracing_thresh = tracing_thresh;
+
+	/* tracing_thresh is in nsecs, we speak in usecs */
+	if (!tracing_thresh)
+		tracing_thresh = last_tracing_thresh;
+
+	if (tracer_tracing_is_on(tr))
+		hwlat_tracer_start(tr);
+
+	hwlat_busy = true;
+
+	return 0;
+}
+
+static void hwlat_tracer_reset(struct trace_array *tr)
+{
+	stop_kthread();
+
+	/* the tracing threshold is static between runs */
+	last_tracing_thresh = tracing_thresh;
+
+	tracing_thresh = save_tracing_thresh;
+	hwlat_busy = false;
+}
+
+static struct tracer hwlat_tracer __read_mostly =
+{
+	.name		= "hwlat",
+	.init		= hwlat_tracer_init,
+	.reset		= hwlat_tracer_reset,
+	.start		= hwlat_tracer_start,
+	.stop		= hwlat_tracer_stop,
+	.allow_instances = true,
+};
+
+__init static int init_hwlat_tracer(void)
+{
+	int ret;
+
+	mutex_init(&hwlat_data.lock);
+
+	ret = register_tracer(&hwlat_tracer);
+	if (ret)
+		return ret;
+
+	init_tracefs();
+
+	return 0;
+}
+late_initcall(init_hwlat_tracer);
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 0bb9cf2d53e6..d67a562df259 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -1098,6 +1098,57 @@ static struct trace_event trace_user_stack_event = {
 	.funcs		= &trace_user_stack_funcs,
 };
 
+/* TRACE_HWLAT */
+static enum print_line_t
+trace_hwlat_print(struct trace_iterator *iter, int flags,
+		  struct trace_event *event)
+{
+	struct trace_entry *entry = iter->ent;
+	struct trace_seq *s = &iter->seq;
+	struct hwlat_entry *field;
+
+	trace_assign_type(field, entry);
+
+	trace_seq_printf(s, "#%-5u inner/outer(us): %4llu/%-5llu ts:%ld.%09ld\n",
+			 field->seqnum,
+			 field->duration,
+			 field->outer_duration,
+			 field->timestamp.tv_sec,
+			 field->timestamp.tv_nsec);
+
+	return trace_handle_return(s);
+}
+
+
+static enum print_line_t
+trace_hwlat_raw(struct trace_iterator *iter, int flags,
+		struct trace_event *event)
+{
+	struct hwlat_entry *field;
+	struct trace_seq *s = &iter->seq;
+
+	trace_assign_type(field, iter->ent);
+
+	trace_seq_printf(s, "%llu %lld %ld %09ld %u\n",
+			 field->duration,
+			 field->outer_duration,
+			 field->timestamp.tv_sec,
+			 field->timestamp.tv_nsec,
+			 field->seqnum);
+
+	return trace_handle_return(s);
+}
+
+static struct trace_event_functions trace_hwlat_funcs = {
+	.trace		= trace_hwlat_print,
+	.raw		= trace_hwlat_raw,
+};
+
+static struct trace_event trace_hwlat_event = {
+	.type		= TRACE_HWLAT,
+	.funcs		= &trace_hwlat_funcs,
+};
+
 /* TRACE_BPUTS */
 static enum print_line_t
 trace_bputs_print(struct trace_iterator *iter, int flags,
@@ -1233,6 +1284,7 @@ static struct trace_event *events[] __initdata = {
 	&trace_bputs_event,
 	&trace_bprint_event,
 	&trace_print_event,
+	&trace_hwlat_event,
 	NULL
 };
 
-- 
2.8.1

[for-next][PATCH 5/7] tracing: Add documentation for hwlat_detector tracer

[Steven Rostedt]

[-- Attachment #1: 0005-tracing-Add-documentation-for-hwlat_detector-tracer.patch --]
[-- Type: text/plain, Size: 4251 bytes --]

From: Jon Masters <jcm@redhat.com>

Added the documentation on how to use th hwlat_detector.

Signed-off-by: Jon Masters <jcm@redhat.com>
[ Various updates and modified to show hwlat as a tracer ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 Documentation/trace/hwlat_detector.txt | 73 ++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 Documentation/trace/hwlat_detector.txt

diff --git a/Documentation/trace/hwlat_detector.txt b/Documentation/trace/hwlat_detector.txt
new file mode 100644
index 000000000000..c02e8ef800cf
--- /dev/null
+++ b/Documentation/trace/hwlat_detector.txt
@@ -0,0 +1,73 @@
+Introduction:
+-------------
+
+The tracer hwlat_detector is a special purpose tracer that is used to
+detect large system latencies induced by the behavior of certain underlying
+hardware or firmware, independent of Linux itself. The code was developed
+originally to detect SMIs (System Management Interrupts) on x86 systems,
+however there is nothing x86 specific about this patchset. It was
+originally written for use by the "RT" patch since the Real Time
+kernel is highly latency sensitive.
+
+SMIs are not serviced by the Linux kernel, which means that it does not
+even know that they are occuring. SMIs are instead set up by BIOS code
+and are serviced by BIOS code, usually for "critical" events such as
+management of thermal sensors and fans. Sometimes though, SMIs are used for
+other tasks and those tasks can spend an inordinate amount of time in the
+handler (sometimes measured in milliseconds). Obviously this is a problem if
+you are trying to keep event service latencies down in the microsecond range.
+
+The hardware latency detector works by hogging one of the cpus for configurable
+amounts of time (with interrupts disabled), polling the CPU Time Stamp Counter
+for some period, then looking for gaps in the TSC data. Any gap indicates a
+time when the polling was interrupted and since the interrupts are disabled,
+the only thing that could do that would be an SMI or other hardware hiccup
+(or an NMI, but those can be tracked).
+
+Note that the hwlat detector should *NEVER* be used in a production environment.
+It is intended to be run manually to determine if the hardware platform has a
+problem with long system firmware service routines.
+
+Usage:
+------
+
+Write the ASCII text "hwlat" into the current_tracer file of the tracing system
+(mounted at /sys/kernel/tracing or /sys/kernel/tracing). It is possible to
+redefine the threshold in microseconds (us) above which latency spikes will
+be taken into account.
+
+Example:
+
+	# echo hwlat > /sys/kernel/tracing/current_tracer
+	# echo 100 > /sys/kernel/tracing/tracing_thresh
+
+The /sys/kernel/tracing/hwlat_detector interface contains the following files:
+
+width			- time period to sample with CPUs held (usecs)
+			  must be less than the total window size (enforced)
+window			- total period of sampling, width being inside (usecs)
+
+By default the width is set to 500,000 and window to 1,000,000, meaning that
+for every 1,000,000 usecs (1s) the hwlat detector will spin for 500,000 usecs
+(0.5s). If tracing_thresh contains zero when hwlat tracer is enabled, it will
+change to a default of 10 usecs. If any latencies that exceed the threshold is
+observed then the data will be written to the tracing ring buffer.
+
+The minimum sleep time between periods is 1 millisecond. Even if width
+is less than 1 millisecond apart from window, to allow the system to not
+be totally starved.
+
+If tracing_thresh was zero when hwlat detector was started, it will be set
+back to zero if another tracer is loaded. Note, the last value in
+tracing_thresh that hwlat detector had will be saved and this value will
+be restored in tracing_thresh if it is still zero when hwlat detector is
+started again.
+
+The following tracing directory files are used by the hwlat_detector:
+
+in /sys/kernel/tracing:
+
+ tracing_threshold	- minimum latency value to be considered (usecs)
+ tracing_max_latency	- maximum hardware latency actually observed (usecs)
+ hwlat_detector/width	- specified amount of time to spin within window (usecs)
+ hwlat_detector/window	- amount of time between (width) runs (usecs)
-- 
2.8.1

[for-next][PATCH 6/7] tracing: Have hwlat trace migrate across tracing_cpumask CPUs

[Steven Rostedt]

[-- Attachment #1: 0006-tracing-Have-hwlat-trace-migrate-across-tracing_cpum.patch --]
[-- Type: text/plain, Size: 3611 bytes --]

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

Instead of having the hwlat detector thread stay on one CPU, have it migrate
across all the CPUs specified by tracing_cpumask. If the user modifies the
thread's CPU affinity, the migration will stop until the next instance that
the tracer is instantiated. The migration happens at the end of each window
(period).

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 Documentation/trace/hwlat_detector.txt |  6 ++++
 kernel/trace/trace_hwlat.c             | 55 ++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+)

diff --git a/Documentation/trace/hwlat_detector.txt b/Documentation/trace/hwlat_detector.txt
index c02e8ef800cf..3207717a0d1a 100644
--- a/Documentation/trace/hwlat_detector.txt
+++ b/Documentation/trace/hwlat_detector.txt
@@ -69,5 +69,11 @@ in /sys/kernel/tracing:
 
  tracing_threshold	- minimum latency value to be considered (usecs)
  tracing_max_latency	- maximum hardware latency actually observed (usecs)
+ tracing_cpumask	- the CPUs to move the hwlat thread across
  hwlat_detector/width	- specified amount of time to spin within window (usecs)
  hwlat_detector/window	- amount of time between (width) runs (usecs)
+
+The hwlat detector's kernel thread will migrate across each CPU specified in
+tracing_cpumask between each window. To limit the migration, either modify
+tracing_cpumask, or modify the hwlat kernel thread (named [hwlatd]) CPU
+affinity directly, and the migration will stop.
diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
index 08dfabe4e862..65aab3914a56 100644
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -42,6 +42,7 @@
 #include <linux/kthread.h>
 #include <linux/tracefs.h>
 #include <linux/uaccess.h>
+#include <linux/cpumask.h>
 #include <linux/delay.h>
 #include "trace.h"
 
@@ -211,6 +212,57 @@ out:
 	return ret;
 }
 
+static struct cpumask save_cpumask;
+static bool disable_migrate;
+
+static void move_to_next_cpu(void)
+{
+	static struct cpumask *current_mask;
+	int next_cpu;
+
+	if (disable_migrate)
+		return;
+
+	/* Just pick the first CPU on first iteration */
+	if (!current_mask) {
+		current_mask = &save_cpumask;
+		get_online_cpus();
+		cpumask_and(current_mask, cpu_online_mask, tracing_buffer_mask);
+		put_online_cpus();
+		next_cpu = cpumask_first(current_mask);
+		goto set_affinity;
+	}
+
+	/*
+	 * If for some reason the user modifies the CPU affinity
+	 * of this thread, than stop migrating for the duration
+	 * of the current test.
+	 */
+	if (!cpumask_equal(current_mask, &current->cpus_allowed))
+		goto disable;
+
+	get_online_cpus();
+	cpumask_and(current_mask, cpu_online_mask, tracing_buffer_mask);
+	next_cpu = cpumask_next(smp_processor_id(), current_mask);
+	put_online_cpus();
+
+	if (next_cpu >= nr_cpu_ids)
+		next_cpu = cpumask_first(current_mask);
+
+ set_affinity:
+	if (next_cpu >= nr_cpu_ids) /* Shouldn't happen! */
+		goto disable;
+
+	cpumask_clear(current_mask);
+	cpumask_set_cpu(next_cpu, current_mask);
+
+	sched_setaffinity(0, current_mask);
+	return;
+
+ disable:
+	disable_migrate = true;
+}
+
 /*
  * kthread_fn - The CPU time sampling/hardware latency detection kernel thread
  *
@@ -230,6 +282,8 @@ static int kthread_fn(void *data)
 
 	while (!kthread_should_stop()) {
 
+		move_to_next_cpu();
+
 		local_irq_disable();
 		get_sample();
 		local_irq_enable();
@@ -473,6 +527,7 @@ static int hwlat_tracer_init(struct trace_array *tr)
 
 	hwlat_trace = tr;
 
+	disable_migrate = false;
 	hwlat_data.count = 0;
 	tr->max_latency = 0;
 	save_tracing_thresh = tracing_thresh;
-- 
2.8.1

[for-next][PATCH 7/7] tracing: Add NMI tracing in hwlat detector

[Steven Rostedt]

[-- Attachment #1: 0007-tracing-Add-NMI-tracing-in-hwlat-detector.patch --]
[-- Type: text/plain, Size: 8452 bytes --]

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

As NMIs can also cause latency when interrupts are disabled, the hwlat
detectory has no way to know if the latency it detects is from an NMI or an
SMI or some other hardware glitch.

As ftrace_nmi_enter/exit() funtions are no longer used (except for sh, which
isn't supported anymore), I converted those to "arch_ftrace_nmi_enter/exit"
and use ftrace_nmi_enter/exit() to check if hwlat detector is tracing or
not, and if so, it calls into the hwlat utility.

Since the hwlat detector only has a single kthread that is spinning with
interrupts disabled, it marks what CPU it is on, and if the NMI callback
happens on that CPU, it records the time spent in that NMI. This is added to
the output that is generated by the hwlat detector as:

 #3     inner/outer(us):    9/9     ts:1470836488.206734548
 #4     inner/outer(us):    0/8     ts:1470836497.140808588
 #5     inner/outer(us):    0/6     ts:1470836499.140825168 nmi-total:5 nmi-count:1
 #6     inner/outer(us):    9/9     ts:1470836501.140841748

All time is still tracked in microseconds.

The NMI information is only shown when an NMI occurred during the sample.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 arch/sh/kernel/ftrace.c      |  4 ++--
 include/linux/ftrace_irq.h   | 31 +++++++++++++++++++++++----
 kernel/trace/trace_entries.h |  8 +++++--
 kernel/trace/trace_hwlat.c   | 51 ++++++++++++++++++++++++++++++++++++++++++++
 kernel/trace/trace_output.c  | 16 +++++++++++++-
 5 files changed, 101 insertions(+), 9 deletions(-)

diff --git a/arch/sh/kernel/ftrace.c b/arch/sh/kernel/ftrace.c
index 38993e09ef03..deb9eba3a43d 100644
--- a/arch/sh/kernel/ftrace.c
+++ b/arch/sh/kernel/ftrace.c
@@ -139,7 +139,7 @@ static void ftrace_mod_code(void)
 		clear_mod_flag();
 }
 
-void ftrace_nmi_enter(void)
+void arch_ftrace_nmi_enter(void)
 {
 	if (atomic_inc_return(&nmi_running) & MOD_CODE_WRITE_FLAG) {
 		smp_rmb();
@@ -150,7 +150,7 @@ void ftrace_nmi_enter(void)
 	smp_mb();
 }
 
-void ftrace_nmi_exit(void)
+void arch_ftrace_nmi_exit(void)
 {
 	/* Finish all executions before clearing nmi_running */
 	smp_mb();
diff --git a/include/linux/ftrace_irq.h b/include/linux/ftrace_irq.h
index dca7bf8cffe2..4ec2c9b205f2 100644
--- a/include/linux/ftrace_irq.h
+++ b/include/linux/ftrace_irq.h
@@ -3,11 +3,34 @@
 
 
 #ifdef CONFIG_FTRACE_NMI_ENTER
-extern void ftrace_nmi_enter(void);
-extern void ftrace_nmi_exit(void);
+extern void arch_ftrace_nmi_enter(void);
+extern void arch_ftrace_nmi_exit(void);
 #else
-static inline void ftrace_nmi_enter(void) { }
-static inline void ftrace_nmi_exit(void) { }
+static inline void arch_ftrace_nmi_enter(void) { }
+static inline void arch_ftrace_nmi_exit(void) { }
 #endif
 
+#ifdef CONFIG_HWLAT_TRACER
+extern bool trace_hwlat_callback_enabled;
+extern void trace_hwlat_callback(bool enter);
+#endif
+
+static inline void ftrace_nmi_enter(void)
+{
+#ifdef CONFIG_HWLAT_TRACER
+	if (trace_hwlat_callback_enabled)
+		trace_hwlat_callback(true);
+#endif
+	arch_ftrace_nmi_enter();
+}
+
+static inline void ftrace_nmi_exit(void)
+{
+	arch_ftrace_nmi_exit();
+#ifdef CONFIG_HWLAT_TRACER
+	if (trace_hwlat_callback_enabled)
+		trace_hwlat_callback(false);
+#endif
+}
+
 #endif /* _LINUX_FTRACE_IRQ_H */
diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
index 70d47dd99359..d1cc37e78f99 100644
--- a/kernel/trace/trace_entries.h
+++ b/kernel/trace/trace_entries.h
@@ -330,18 +330,22 @@ FTRACE_ENTRY(hwlat, hwlat_entry,
 	F_STRUCT(
 		__field(	u64,			duration	)
 		__field(	u64,			outer_duration	)
+		__field(	u64,			nmi_total_ts	)
 		__field_struct( struct timespec,	timestamp	)
 		__field_desc(	long,	timestamp,	tv_sec		)
 		__field_desc(	long,	timestamp,	tv_nsec		)
+		__field(	unsigned int,		nmi_count	)
 		__field(	unsigned int,		seqnum		)
 	),
 
-	F_printk("cnt:%u\tts:%010lu.%010lu\tinner:%llu\touter:%llu\n",
+	F_printk("cnt:%u\tts:%010lu.%010lu\tinner:%llu\touter:%llunmi-ts:%llu\tnmi-count:%u\n",
 		 __entry->seqnum,
 		 __entry->tv_sec,
 		 __entry->tv_nsec,
 		 __entry->duration,
-		 __entry->outer_duration),
+		 __entry->outer_duration,
+		 __entry->nmi_total_ts,
+		 __entry->nmi_count),
 
 	FILTER_OTHER
 );
diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
index 65aab3914a56..b97286c48735 100644
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -64,6 +64,15 @@ static struct dentry *hwlat_sample_window;	/* sample window us */
 /* Save the previous tracing_thresh value */
 static unsigned long save_tracing_thresh;
 
+/* NMI timestamp counters */
+static u64 nmi_ts_start;
+static u64 nmi_total_ts;
+static int nmi_count;
+static int nmi_cpu;
+
+/* Tells NMIs to call back to the hwlat tracer to record timestamps */
+bool trace_hwlat_callback_enabled;
+
 /* If the user changed threshold, remember it */
 static u64 last_tracing_thresh = DEFAULT_LAT_THRESHOLD * NSEC_PER_USEC;
 
@@ -72,7 +81,9 @@ struct hwlat_sample {
 	u64		seqnum;		/* unique sequence */
 	u64		duration;	/* delta */
 	u64		outer_duration;	/* delta (outer loop) */
+	u64		nmi_total_ts;	/* Total time spent in NMIs */
 	struct timespec	timestamp;	/* wall time */
+	int		nmi_count;	/* # NMIs during this sample */
 };
 
 /* keep the global state somewhere. */
@@ -112,6 +123,8 @@ static void trace_hwlat_sample(struct hwlat_sample *sample)
 	entry->duration			= sample->duration;
 	entry->outer_duration		= sample->outer_duration;
 	entry->timestamp		= sample->timestamp;
+	entry->nmi_total_ts		= sample->nmi_total_ts;
+	entry->nmi_count		= sample->nmi_count;
 
 	if (!call_filter_check_discard(call, entry, buffer, event))
 		__buffer_unlock_commit(buffer, event);
@@ -125,6 +138,26 @@ static void trace_hwlat_sample(struct hwlat_sample *sample)
 #define init_time(a, b)	(a = b)
 #define time_u64(a)	a
 
+void trace_hwlat_callback(bool enter)
+{
+	if (smp_processor_id() != nmi_cpu)
+		return;
+
+	/*
+	 * Currently trace_clock_local() calls sched_clock() and the
+	 * generic version is not NMI safe.
+	 */
+	if (!IS_ENABLED(CONFIG_GENERIC_SCHED_CLOCK)) {
+		if (enter)
+			nmi_ts_start = time_get();
+		else
+			nmi_total_ts = time_get() - nmi_ts_start;
+	}
+
+	if (enter)
+		nmi_count++;
+}
+
 /**
  * get_sample - sample the CPU TSC and look for likely hardware latencies
  *
@@ -144,6 +177,14 @@ static int get_sample(void)
 
 	do_div(thresh, NSEC_PER_USEC); /* modifies interval value */
 
+	nmi_cpu = smp_processor_id();
+	nmi_total_ts = 0;
+	nmi_count = 0;
+	/* Make sure NMIs see this first */
+	barrier();
+
+	trace_hwlat_callback_enabled = true;
+
 	init_time(last_t2, 0);
 	start = time_get(); /* start timestamp */
 
@@ -188,6 +229,10 @@ static int get_sample(void)
 
 	} while (total <= hwlat_data.sample_width);
 
+	barrier(); /* finish the above in the view for NMIs */
+	trace_hwlat_callback_enabled = false;
+	barrier(); /* Make sure nmi_total_ts is no longer updated */
+
 	ret = 0;
 
 	/* If we exceed the threshold value, we have found a hardware latency */
@@ -196,11 +241,17 @@ static int get_sample(void)
 
 		ret = 1;
 
+		/* We read in microseconds */
+		if (nmi_total_ts)
+			do_div(nmi_total_ts, NSEC_PER_USEC);
+
 		hwlat_data.count++;
 		s.seqnum = hwlat_data.count;
 		s.duration = sample;
 		s.outer_duration = outer_sample;
 		s.timestamp = CURRENT_TIME;
+		s.nmi_total_ts = nmi_total_ts;
+		s.nmi_count = nmi_count;
 		trace_hwlat_sample(&s);
 
 		/* Keep a running maximum ever recorded hardware latency */
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index d67a562df259..3fc20422c166 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -1109,13 +1109,27 @@ trace_hwlat_print(struct trace_iterator *iter, int flags,
 
 	trace_assign_type(field, entry);
 
-	trace_seq_printf(s, "#%-5u inner/outer(us): %4llu/%-5llu ts:%ld.%09ld\n",
+	trace_seq_printf(s, "#%-5u inner/outer(us): %4llu/%-5llu ts:%ld.%09ld",
 			 field->seqnum,
 			 field->duration,
 			 field->outer_duration,
 			 field->timestamp.tv_sec,
 			 field->timestamp.tv_nsec);
 
+	if (field->nmi_count) {
+		/*
+		 * The generic sched_clock() is not NMI safe, thus
+		 * we only record the count and not the time.
+		 */
+		if (!IS_ENABLED(CONFIG_GENERIC_SCHED_CLOCK))
+			trace_seq_printf(s, " nmi-total:%llu",
+					 field->nmi_total_ts);
+		trace_seq_printf(s, " nmi-count:%u",
+				 field->nmi_count);
+	}
+
+	trace_seq_putc(s, '\n');
+
 	return trace_handle_return(s);
 }
 
-- 
2.8.1