RE: [PATCH 1/3] [POC] test implementaion of rt-signals

[Johannes Kirchmair <johannes.kirchmair@sigmatek.at>]

> -----Original Message-----
> From: Jan Kiszka <jan.kiszka@siemens.com>
> Sent: Donnerstag, 7. September 2023 15:40
> To: Johannes Kirchmair <johannes.kirchmair@sigmatek.at>;
> xenomai@lists.linux.dev
> Subject: Re: [PATCH 1/3] [POC] test implementaion of rt-signals
> 
> CAUTION: External E-Mail !
> 
> On 04.09.23 08:55, Johannes Kirchmair wrote:
> > Hi Jan,
> >
> >> -----Original Message-----
> >> From: Jan Kiszka <jan.kiszka@siemens.com>
> >> Sent: Freitag, 1. September 2023 14:00
> >> To: Johannes Kirchmair <johannes.kirchmair@sigmatek.at>;
> >> xenomai@lists.linux.dev
> >> Subject: Re: [PATCH 1/3] [POC] test implementaion of rt-signals
> >>
> >> CAUTION: External E-Mail !
> >>
> >> On 16.08.23 12:18, Johannes Kirchmair wrote:
> >>> We implement rt signals to handle exceptions in rt stage.
> >>>
> >>> This is done using dovetail specific functions for setting up the signal
> >>> frame.
> >>>
> >>> This can be used to handle fpe exceptions on the fly, like fixing
> >>> division by zero. An other use case are breakpoints, implemented using the
> >>> illegal opcode exception. The real time handling of the breakpoints would
> >>> be handy for conditional breakpoints or also for stopping watchdogs and
> >>> other tasks in time.
> >>>
> >>> Signed-off-by: Johannes Kirchmair <johannes.kirchmair@sigmatek.at>
> >>> ---
> >>>  include/cobalt/kernel/ppd.h                   |  3 +
> >>>  include/cobalt/kernel/thread.h                |  2 +
> >>>  include/cobalt/signal.h                       |  2 +
> >>>  include/cobalt/uapi/signal.h                  |  1 +
> >>>  include/cobalt/uapi/syscall.h                 |  6 ++
> >>>  kernel/cobalt/arch/x86/Makefile               |  2 +-
> >>>  .../arch/x86/include/asm/xenomai/thread.h     | 13 ++++
> >>>  kernel/cobalt/arch/x86/signal_ia32.c          | 75 +++++++++++++++++++
> >>>  kernel/cobalt/arch/x86/signal_ia64.c          | 37 +++++++++
> >>>  kernel/cobalt/dovetail/kevents.c              |  5 ++
> >>>  kernel/cobalt/posix/process.c                 |  3 +-
> >>>  kernel/cobalt/posix/syscall.c                 | 28 +++++++
> >>>  kernel/cobalt/posix/syscall32.c               | 16 ++++
> >>>  kernel/cobalt/thread.c                        | 39 ++++++++++
> >>>  lib/cobalt/arch/x86/Makefile.am               |  2 +-
> >>>  lib/cobalt/arch/x86/sigreturn.c               | 36 +++++++++
> >>>  lib/cobalt/internal.h                         |  2 +
> >>>  lib/cobalt/signal.c                           | 13 ++++
> >>>  18 files changed, 282 insertions(+), 3 deletions(-)
> >>>  create mode 100644 kernel/cobalt/arch/x86/signal_ia32.c
> >>>  create mode 100644 kernel/cobalt/arch/x86/signal_ia64.c
> >>>  create mode 100644 lib/cobalt/arch/x86/sigreturn.c
> >>>
> >>> diff --git a/include/cobalt/kernel/ppd.h b/include/cobalt/kernel/ppd.h
> >>> index f0079fe6e..fb2f682da 100644
> >>> --- a/include/cobalt/kernel/ppd.h
> >>> +++ b/include/cobalt/kernel/ppd.h
> >>> @@ -22,6 +22,7 @@
> >>>  #include <linux/types.h>
> >>>  #include <linux/atomic.h>
> >>>  #include <linux/rbtree.h>
> >>> +#include <linux/signal.h>
> >>>  #include <cobalt/kernel/heap.h>
> >>>
> >>>  struct cobalt_umm {
> >>> @@ -32,6 +33,8 @@ struct cobalt_umm {
> >>>
> >>>  struct cobalt_ppd {
> >>>       struct cobalt_umm umm;
> >>> +     void __user *sighand[_NSIG];
> >>> +     void __user *sigrestorer;
> >>>       atomic_t refcnt;
> >>>       char *exe_path;
> >>>       struct rb_root fds;
> >>> diff --git a/include/cobalt/kernel/thread.h b/include/cobalt/kernel/thread.h
> >>> index b79cb8429..33d468419 100644
> >>> --- a/include/cobalt/kernel/thread.h
> >>> +++ b/include/cobalt/kernel/thread.h
> >>> @@ -574,6 +574,8 @@ static inline void
> >> xnthread_propagate_schedparam(struct xnthread *curr)
> >>>               __xnthread_propagate_schedparam(curr);
> >>>  }
> >>>
> >>> +int xnthread_handle_rt_signals(unsigned int trapnr, struct pt_regs *regs);
> >>> +
> >>>  extern struct xnthread_personality xenomai_personality;
> >>>
> >>>  /** @} */
> >>> diff --git a/include/cobalt/signal.h b/include/cobalt/signal.h
> >>> index 62694f93a..3d6540aff 100644
> >>> --- a/include/cobalt/signal.h
> >>> +++ b/include/cobalt/signal.h
> >>> @@ -54,6 +54,8 @@ COBALT_DECL(int, kill(pid_t pid, int sig));
> >>>  COBALT_DECL(int, sigqueue(pid_t pid, int sig,
> >>>                         const union sigval value));
> >>>
> >>> +int cobalt_rt_signal(int sig, void (*handler)(int, siginfo_t *, void *));
> >>> +
> >>>  #ifdef __cplusplus
> >>>  }
> >>>  #endif
> >>> diff --git a/include/cobalt/uapi/signal.h b/include/cobalt/uapi/signal.h
> >>> index 8a7ea15a4..1afb6050a 100644
> >>> --- a/include/cobalt/uapi/signal.h
> >>> +++ b/include/cobalt/uapi/signal.h
> >>> @@ -68,6 +68,7 @@
> >>>  #define SIGDEBUG_RESCNT_IMBALANCE    7
> >>>  #define SIGDEBUG_LOCK_BREAK          8
> >>>  #define SIGDEBUG_MUTEX_SLEEP         9
> >>> +#define SIGDEBUG_SIGRESTOR           10
> >>>
> >>>  #define COBALT_DELAYMAX                      2147483647U
> >>>
> >>> diff --git a/include/cobalt/uapi/syscall.h b/include/cobalt/uapi/syscall.h
> >>> index 3e65efaab..f14bd8ffe 100644
> >>> --- a/include/cobalt/uapi/syscall.h
> >>> +++ b/include/cobalt/uapi/syscall.h
> >>> @@ -142,6 +142,12 @@
> >>>  #define sc_cobalt_timerfd_gettime64          119
> >>>  #define sc_cobalt_pselect64                  120
> >>>
> >>> +/*
> >>> + * Sigmatek specific syscalls
> >>> + */
> >>> +#define sc_cobalt_sigreturn                  121
> >>> +#define sc_cobalt_sigaction                  122
> >>> +
> >>>  #define __NR_COBALT_SYSCALLS                 128 /* Power of 2 */
> >>>
> >>>  #endif /* !_COBALT_UAPI_SYSCALL_H */
> >>> diff --git a/kernel/cobalt/arch/x86/Makefile
> b/kernel/cobalt/arch/x86/Makefile
> >>> index 93929b645..e725afbff 100644
> >>> --- a/kernel/cobalt/arch/x86/Makefile
> >>> +++ b/kernel/cobalt/arch/x86/Makefile
> >>> @@ -1,5 +1,5 @@
> >>>
> >>>  obj-$(CONFIG_XENOMAI) += xenomai.o
> >>> -xenomai-y := machine.o smi.o c1e.o
> >>> +xenomai-y := machine.o smi.o c1e.o signal_ia32.o signal_ia64.o
> >>>
> >>>  ccflags-y := -I$(srctree)/arch/x86/xenomai/include -
> >> I$(srctree)/include/xenomai
> >>> diff --git a/kernel/cobalt/arch/x86/include/asm/xenomai/thread.h
> >> b/kernel/cobalt/arch/x86/include/asm/xenomai/thread.h
> >>> index 745c32467..4d004680b 100644
> >>> --- a/kernel/cobalt/arch/x86/include/asm/xenomai/thread.h
> >>> +++ b/kernel/cobalt/arch/x86/include/asm/xenomai/thread.h
> >>> @@ -28,5 +28,18 @@
> >>>  #define xnarch_fault_bp_p(__nr)              ((current->ptrace & PT_PTRACED)
> &&
> >> \
> >>>                                        ((__nr) == X86_TRAP_DB || (__nr) == X86_TRAP_BP))
> >>>  #define xnarch_fault_notify(__nr)    (!xnarch_fault_bp_p(__nr))
> >>> +#define xnarch_fault_code(__regs)            ((__regs)->orig_ax)
> >>> +int xnarch_setup_trap_info(unsigned int vector, struct pt_regs *regs,
> >>> +                        long errcode, int *sig, struct kernel_siginfo *info);
> >>> +
> >>> +int xnarch_setup_rt_frame_ia32(int sig, void *handler, struct kernel_siginfo
> >> *si,
> >>> +                       struct pt_regs *regs, void __user *restorer);
> >>> +
> >>> +int xnarch_rt_sigreturn_ia32(struct pt_regs *regs);
> >>> +
> >>> +int xnarch_setup_rt_frame_ia64(int sig, void *handler, struct kernel_siginfo
> >> *si,
> >>> +                       struct pt_regs *regs, void __user *restorer);
> >>> +
> >>> +int xnarch_rt_sigreturn_ia64(struct pt_regs *regs);
> >>>
> >>>  #endif /* !_COBALT_X86_ASM_THREAD_H */
> >>> diff --git a/kernel/cobalt/arch/x86/signal_ia32.c
> >> b/kernel/cobalt/arch/x86/signal_ia32.c
> >>> new file mode 100644
> >>> index 000000000..140016460
> >>> --- /dev/null
> >>> +++ b/kernel/cobalt/arch/x86/signal_ia32.c
> >>> @@ -0,0 +1,75 @@
> >>> +#include <linux/signal.h>
> >>> +#include <linux/uaccess.h>
> >>> +#include <cobalt/kernel/thread.h>
> >>> +
> >>> +#include <asm/sigframe.h>
> >>> +#include <asm/sighandling.h>
> >>> +#include <asm/fpu/signal.h>
> >>> +
> >>> +int xnarch_setup_trap_info(unsigned int vector, struct pt_regs *regs,
> >>> +                        long errcode, int *sig, struct kernel_siginfo *info)
> >>
> >> Why is this function in file that suggests to handle only 32-bit? It's
> >> shared by both 32 and 64 bit.
> > Did not changed it yet?
> > Should I add an distinct signal.c file for the function?
> 
> Yes, that would be logical in this case.
Actually noticed that I do exactly the same in xnarch_rt_sigreturn_ia32
and xnarch_rt_sigreturn_ia64 so I moved this to generic code.
And moved the xnarch_setup_trap_info to signal.c

Will post new patches, where I fixed some of the complains in the previous mails, tomorrow.
> 
> >
> >>
> >>> +{
> >>> +     switch (vector) {
> >>> +     case 0: /* divide_error */
> >>> +             *sig = SIGFPE;
> >>> +             info->si_signo = *sig;
> >>> +             info->si_errno = 0;
> >>> +             info->si_code = FPE_INTDIV;
> >>> +             info->si_addr = (void __user *)regs->ip;
> >>> +             return 0;
> >>> +     case 1: /* trap_error */ {
> >>> +             unsigned long condition;
> >>> +             get_debugreg(condition, 6);
> >>> +             set_debugreg(0, 7);
> >>> +             *sig = SIGTRAP;
> >>> +             info->si_signo = *sig;
> >>> +             info->si_errno = errcode;
> >>> +             info->si_code = get_si_code(condition);
> >>> +             info->si_addr = (void __user *)regs->ip;
> >>> +             return 0;
> >>> +     }
> >>> +     case 3: /* trap_error */
> >>> +             *sig = SIGTRAP;
> >>> +             info->si_signo = *sig;
> >>> +             info->si_errno = errcode;
> >>> +             info->si_code = SI_KERNEL;
> >>> +             info->si_addr = (void __user *)regs->ip;
> >>> +             return 0;
> >>> +     case 6: /* invalid_op */
> >>> +             *sig = SIGILL;
> >>> +             info->si_signo = *sig;
> >>> +             info->si_errno = 0;
> >>> +             info->si_code = ILL_ILLOPN;
> >>> +             info->si_addr = (void __user *)regs->ip;
> >>> +             return 0;
> >>> +     case 16: { /* coprocessor_error */
> >>> +             *sig = SIGFPE;
> >>> +
> >>> +             info->si_signo = *sig;
> >>> +             info->si_errno = 0;
> >>> +             info->si_code = 0;
> >>> +             info->si_addr = (void __user *)regs->ip;
> >>> +             return 0;
> >>> +     }
> >>> +     default:
> >>> +             break;
> >>> +     }
> >>> +
> >>> +     return -ENOSYS;
> >>> +}
> >>> +
> >>> +int xnarch_rt_sigreturn_ia32(struct pt_regs *regs)
> >>> +{
> >>> +     int ret;
> >>> +
> >>> +     ret = dovetail_restore_rt_signal_frame(regs);
> >>> +     if (ret < 0)
> >>> +             goto badframe;
> >>> +
> >>> +     return regs->ax;
> >>> +
> >>> +badframe:
> >>> +     xnthread_call_mayday(xnthread_current(), SIGDEBUG_SIGRESTOR);
> >>> +     return -1;
> >>> +}
> >>> +
> >>> diff --git a/kernel/cobalt/arch/x86/signal_ia64.c
> >> b/kernel/cobalt/arch/x86/signal_ia64.c
> >>> new file mode 100644
> >>> index 000000000..3b8cd3330
> >>> --- /dev/null
> >>> +++ b/kernel/cobalt/arch/x86/signal_ia64.c
> >>> @@ -0,0 +1,37 @@
> >>> +// SPDX-License-Identifier: GPL-2.0
> >>> +/*
> >>> + *  Copyright (C) 1991, 1992  Linus Torvalds
> >>> + *  Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
> >>> + *
> >>> + *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
> >>> + *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
> >>> + *  2000-2002   x86-64 support by Andi Kleen
> >>> + */
> >>> +
> >>> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> >>> +
> >>> +
> >>> +#include <linux/signal.h>
> >>> +#include <linux/uaccess.h>
> >>> +#include <cobalt/kernel/thread.h>
> >>> +
> >>> +#include <asm/sigframe.h>
> >>> +#include <asm/sighandling.h>
> >>> +#include <asm/fpu/signal.h>
> >>> +
> >>> +int xnarch_rt_sigreturn_ia64(struct pt_regs *regs)
> >>> +{
> >>> +     int ret;
> >>> +
> >>> +     ret = dovetail_restore_rt_signal_frame(regs);
> >>> +     if (ret < 0)
> >>> +             goto badframe;
> >>> +
> >>> +     return regs->ax;
> >>> +
> >>> +badframe:
> >>> +     xnthread_call_mayday(xnthread_current(), SIGDEBUG_SIGRESTOR);
> >>
> >> I'm not sure if this is the right way to react. Mayday will translate to
> >> SIGDEBUG, but we need a SIGSEGV.
> >>
> >>> +     return -1;
> >>> +
> >>> +}
> >>> +
> >>> diff --git a/kernel/cobalt/dovetail/kevents.c
> b/kernel/cobalt/dovetail/kevents.c
> >>> index 4da4f51b7..61417717b 100644
> >>> --- a/kernel/cobalt/dovetail/kevents.c
> >>> +++ b/kernel/cobalt/dovetail/kevents.c
> >>> @@ -57,6 +57,9 @@ void handle_oob_trap_entry(unsigned int trapnr, struct
> >> pt_regs *regs)
> >>>               xnsched_run();
> >>>       }
> >>>
> >>> +     if (xnthread_handle_rt_signals(trapnr, regs) == 0)
> >>> +             return;
> >>> +
> >>>       /*
> >>>        * If we experienced a trap on behalf of a shadow thread
> >>>        * running in primary mode, move it to the Linux domain,
> >>> @@ -88,6 +91,8 @@ void handle_oob_trap_entry(unsigned int trapnr, struct
> >> pt_regs *regs)
> >>>               xnstat_counter_inc(&thread->stat.pf);
> >>>
> >>>       xnthread_relax(xnarch_fault_notify(trapnr), SIGDEBUG_MIGRATE_FAULT);
> >>> +
> >>> +     return;
> >>
> >> Unrelated and unneeded change.
> >>
> >>>  }
> >>>
> >>>  static inline int handle_setaffinity_event(struct dovetail_migration_data *d)
> >>> diff --git a/kernel/cobalt/posix/process.c b/kernel/cobalt/posix/process.c
> >>> index 1abc86f37..2069129cb 100644
> >>> --- a/kernel/cobalt/posix/process.c
> >>> +++ b/kernel/cobalt/posix/process.c
> >>> @@ -738,9 +738,10 @@ void cobalt_unregister_debugged_thread(struct
> >> xnthread *thread)
> >>>               cobalt_resume_debugged_process(process);
> >>>  }
> >>>
> >>> +#ifdef CONFIG_SMP
> >>> +
> >>>  int cobalt_handle_setaffinity_event(struct task_struct *task)
> >>>  {
> >>> -#ifdef CONFIG_SMP
> >>
> >> Unrelated and bogus change.
> >>
> >>>       struct xnthread *thread;
> >>>       spl_t s;
> >>>
> >>> diff --git a/kernel/cobalt/posix/syscall.c b/kernel/cobalt/posix/syscall.c
> >>> index 46c4998e4..b4bd4c587 100644
> >>> --- a/kernel/cobalt/posix/syscall.c
> >>> +++ b/kernel/cobalt/posix/syscall.c
> >>> @@ -277,6 +277,34 @@ static COBALT_SYSCALL(serialdbg, current,
> >>>       return 0;
> >>>  }
> >>>
> >>> +static COBALT_SYSCALL(sigreturn, current, (void))
> >>> +{
> >>> +     struct pt_regs *regs = task_pt_regs(current);
> >>> +
> >>> +     if (regs->cs == __USER_CS)
> >>> +             xnarch_rt_sigreturn_ia64(regs);
> >>> +     if (regs->cs == __USER32_CS)
> >>> +             xnarch_rt_sigreturn_ia32(regs);
> >>> +
> >>> +     return __xn_reg_rval(regs);
> >>> +}
> >>> +
> >>> +static COBALT_SYSCALL(sigaction, current, (int sig, void __user *handler,
> >>> +                   void __user *restorer))
> >>> +{
> >>> +     struct cobalt_ppd *sys_ppd = cobalt_ppd_get(0);
> >>> +
> >>> +     if (sig < 0 || sig >= _NSIG)
> >>> +             return -EINVAL;
> >>> +
> >>> +     sys_ppd->sighand[sig] = handler;
> >>> +
> >>> +     if (!sys_ppd->sigrestorer)
> >>> +             sys_ppd->sigrestorer = restorer;
> >>> +
> >>> +     return 0;
> >>> +}
> >>> +
> >>>  static void stringify_feature_set(unsigned long fset, char *buf, int size)
> >>>  {
> >>>       unsigned long feature;
> >>> diff --git a/kernel/cobalt/posix/syscall32.c b/kernel/cobalt/posix/syscall32.c
> >>> index 780d276b1..7c858f904 100644
> >>> --- a/kernel/cobalt/posix/syscall32.c
> >>> +++ b/kernel/cobalt/posix/syscall32.c
> >>> @@ -705,6 +705,22 @@ COBALT_SYSCALL32emu(sigqueue, conforming,
> >>>       return ret ?: __cobalt_sigqueue(pid, sig, &val);
> >>>  }
> >>>
> >>> +COBALT_SYSCALL32emu(sigaction, current,
> >>> +                 (int sig, void __user *handler, void __user *restorer))
> >>> +{
> >>> +     struct cobalt_ppd *sys_ppd = cobalt_ppd_get(0);
> >>> +
> >>> +     if (sig < 0 || sig >= _NSIG)
> >>> +             return -EINVAL;
> >>> +
> >>> +     sys_ppd->sighand[sig] = handler;
> >>> +
> >>> +     if (!sys_ppd->sigrestorer)
> >>> +             sys_ppd->sigrestorer = restorer;
> >>> +
> >>> +     return 0;
> >>> +}
> >>> +
> >>>  COBALT_SYSCALL32emu(monitor_wait, nonrestartable,
> >>>                   (struct cobalt_monitor_shadow __user *u_mon,
> >>>                    int event, const struct old_timespec32 __user *u_ts,
> >>> diff --git a/kernel/cobalt/thread.c b/kernel/cobalt/thread.c
> >>> index 41804b24f..71f97c481 100644
> >>> --- a/kernel/cobalt/thread.c
> >>> +++ b/kernel/cobalt/thread.c
> >>> @@ -25,6 +25,7 @@
> >>>  #include <linux/signal.h>
> >>>  #include <linux/pid.h>
> >>>  #include <linux/sched.h>
> >>> +#include <asm/sighandling.h>
> >>>  #include <uapi/linux/sched/types.h>
> >>>  #include <cobalt/kernel/sched.h>
> >>>  #include <cobalt/kernel/timer.h>
> >>> @@ -43,6 +44,7 @@
> >>>  #include <pipeline/inband_work.h>
> >>>  #include <pipeline/sched.h>
> >>>  #include <trace/events/cobalt-core.h>
> >>> +#include "posix/process.h"
> >>>  #include "debug.h"
> >>>
> >>>  static DECLARE_WAIT_QUEUE_HEAD(join_all);
> >>> @@ -2520,6 +2522,43 @@ int xnthread_killall(int grace, int mask)
> >>>  }
> >>>  EXPORT_SYMBOL_GPL(xnthread_killall);
> >>>
> >>> +int xnthread_handle_rt_signals(unsigned int trapnr, struct pt_regs *regs)
> >>> +{
> >>> +     struct ksignal ksig;
> >>> +
> >>> +     unsigned int vector = trapnr;
> >>> +     unsigned int code = xnarch_fault_code(regs);
> >>> +     struct cobalt_ppd *sys_ppd;
> >>> +     int sig, ret = 0;
> >>> +     struct kernel_siginfo si;
> >>> +
> >>> +     code = xnarch_fault_code(regs);
> >>> +     ret = xnarch_setup_trap_info(vector, regs, code, &sig, &si);
> >>> +     if (ret || sig == 0)
> >>> +             return 1;
> >>> +
> >>> +     sys_ppd = cobalt_ppd_get(0);
> >>> +     if (sig >= _NSIG ||
> >>> +         sys_ppd->sighand[sig] == NULL ||
> >>> +         sys_ppd->sighand[sig] == SIG_DFL)
> >>> +             return 1;
> >>> +
> >>> +     if (sys_ppd->sigrestorer == NULL)
> >>> +             return 1;
> >>> +
> >>> +     ksig.sig = sig;
> >>> +     memcpy(&ksig.info, &si, sizeof(si));
> >>> +     ksig.ka.sa.sa_flags = SA_SIGINFO | SA_RESTORER;
> >>> +     ksig.ka.sa.sa_restorer = sys_ppd->sigrestorer;
> >>> +     ksig.ka.sa.sa_handler = sys_ppd->sighand[sig];
> >>> +
> >>> +     ret = dovetail_setup_rt_signal_frame(&ksig, regs);
> >>
> >> All this is called with interrupts off on x86, and that makes dovetail
> >> unhappy:
> >>
> >> [   17.051995] 9pnet: Limiting 'msize' to 512000 as this is the maximum
> supported
> >> by transport virtio
> >> [   37.268218] ------------[ cut here ]------------
> >> [   37.268223] WARNING: CPU: 2 PID: 1402 at ../mm/memory.c:5857
> >> __might_fault+0x95/0xa0
> >> [   37.268237] Modules linked in: 9p netfs rt_e1000 rt_e1000_new rtnet
> >> [   37.268252] CPU: 2 PID: 1402 Comm: rt-task Not tainted 6.5.0+ #40
> >> [   37.268259] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
> rel-
> >> 1.16.0-0-gd239552c-rebuilt.opensuse.org 04/01/2014
> >> [   37.268262] IRQ stage: Xenomai
> >> [   37.268265] RIP: 0010:__might_fault+0x95/0xa0
> >> [   37.268271] Code: b8 a0 01 00 00 e8 cb bf e3 ff 48 8b bb e8 04 00 00 48 8b
> 5d
> >> f8 48 c7 c6 6b 29 2d 81 58 c9 48 81 c7 a0 01 00 00 e9 2b bc e3 ff <0f> 0b eb
> 86
> >> 0f 1f 80 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90
> >> [   37.268277] RSP: 0000:ffffc900007f3cd0 EFLAGS: 00010046
> >> [   37.268283] RAX: 0000000000000006 RBX: 00007f5aa94016b8 RCX:
> >> ffffc900007f3d70
> >> [   37.268287] RDX: 00007f5aa9401cc4 RSI: 00000000000000a7 RDI:
> >> ffffffff82962a10
> >> [   37.268291] RBP: ffffc900007f3cd8 R08: 0000000000000444 R09:
> >> 0000000000000000
> >> [   37.268295] R10: 0000000000000000 R11: 0000000000000000 R12:
> >> 0000000000000000
> >> [   37.268298] R13: ffff888009e6e700 R14: 0000000000000000 R15:
> >> 00000000000299a0
> >> [   37.268302] FS:  00007f5aa9402700(0000) GS:ffff88803ed00000(0000)
> >> knlGS:0000000000000000
> >> [   37.268313] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >> [   37.268317] CR2: 0000560ba8044008 CR3: 000000000981a004 CR4:
> >> 0000000000370ee0
> >> [   37.268321] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
> >> 0000000000000000
> >> [   37.268324] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
> >> 0000000000000400
> >> [   37.268328] Call Trace:
> >> [   37.268332]  <TASK>
> >> [   37.268339]  ? __warn+0x81/0x180
> >> [   37.268350]  ? __might_fault+0x95/0xa0
> >> [   37.268363]  ? report_bug+0x10b/0x200
> >> [   37.268406]  ? handle_bug+0x50/0xc0
> >> [   37.268417]  ? exc_invalid_op+0xc7/0xe0
> >> [   37.268427]  ? asm_exc_invalid_op+0x16/0x20
> >> [   37.268467]  ? __might_fault+0x95/0xa0
> >> [   37.268485]  copy_fpstate_to_sigframe+0x74/0x430
> >> [   37.268496]  ? ___xnsched_run+0x223/0x590
> >> [   37.268515]  ? __pfx____xnsched_run+0x10/0x10
> >> [   37.268541]  get_sigframe+0xea/0x2b0
> >> [   37.268562]  x64_setup_rt_frame+0x68/0x2f0
> >> [   37.268583]  xnthread_handle_rt_signals+0xf8/0x130
> >> [   37.268633]  handle_oob_trap_entry+0xaa/0x3a0
> >> [   37.268640]  ? __pfx_CoBaLt_sigaction+0x10/0x10
> >> [   37.268666]  __oob_trap_notify+0x27/0x30
> >> [   37.268674]  do_error_trap+0x162/0x1d0
> >> [   37.268695]  exc_divide_error+0x35/0x50
> >> [   37.268707]  asm_exc_divide_error+0x16/0x20
> >> [   37.268713] RIP: 0033:0x400e68
> >>
> >> I'm currently scratching my head if we can safely enable hard interrupts
> >> here to resolve this (and the underlying latency source).
> > Not sure what is the right way. Have some problems understanding, what has to
> be protected for the setup to work correct.
> >
> 
> I have a working dovetail patch locally will share it later.
Nice.
> 
> >>
> >> We will also need pagefault_disable in our dovetail functions, already
> >> playing with that.
> > Could you explain to me, what pagefault_disable does and by we need it.
> 
> For us, it primarily signals to the might_sleep() check that we don't
> expect any waiting due to not yet mapped memory - accesses under that
> protection are supposed to succeed or fail immediately. The kernel
> writes: "If disabled, it will not take any locks and go straight to the
> fixup table."
Ok, thx for explaining.

Johannes

> 
> Jan
> 
> --
> Siemens AG, Technology
> Linux Expert Center