[ltt-dev] [PATCH v2] add tracepoints of panic and kexec

[Mathieu Desnoyers]

* Zhaolei (zhaolei at cn.fujitsu.com) wrote:
> * From: "Mathieu Desnoyers" <compudj at krystal.dyndns.org>
> >* Zhaolei (zhaolei at cn.fujitsu.com) wrote:
> >> Instrumentation of following panic and kexec related events are added:
> >> panic
> >> kernel_kexec
> >> crash_kexec
> >> 
> >> It is useful for build flight-recorder program based on lttng infrastructure.
> >> 
> > 
> > Hrm, I'm wondering if these are events we are interested to trace or if
> > you plan to use these tracepoints as hooks into the kernel to connect
> > the tracer infrastructure to it ?
> Hello, Mathieu
> 
> IMHO, both.
> 
> As a programmer who want to build  flight-recorder based on lttng infrastructure,
> he can:
> 1: use lttng trace, and get lttng's trace datas from kernel-dump file.
> or
> 2: use lttng's tracepoint, and record events himself.
> 
> But as a lttng's programmer, we can make both way possible.
> 
> What is your opinion?
> 

Yes, I think having both is good. So we could add, separately :

A hook in panic and kexec using include/linux/notifier.h so mechanisms
other than tracers can connect their hook to it.

Also add a tracepoint so tracers can use this as an event source.

I would do both in separate patches though, because they have different
purposes.

Best regards,

Mathieu


> B.R.
> Zhaolei
> > 
> > If you plan to use those as hooks into the kernel, we should probably
> > consider adding notifiers instead (notifier.h). This is the "blessed"
> > way to be called upon such events.
> > 
> > Mathieu
> > 
> >> Signed-off-by: Zhao Lei <zhaolei at cn.fujitsu.com>
> >> ---
> >>  include/trace/kernel.h |   10 ++++++++++
> >>  kernel/kexec.c         |    8 ++++++++
> >>  kernel/panic.c         |    7 +++++++
> >>  3 files changed, 25 insertions(+), 0 deletions(-)
> >> 
> >> diff --git a/include/trace/kernel.h b/include/trace/kernel.h
> >> index d2c3320..06d585f 100644
> >> --- a/include/trace/kernel.h
> >> +++ b/include/trace/kernel.h
> >> @@ -2,6 +2,7 @@
> >>  #define _TRACE_KERNEL_H
> >>  
> >>  #include <linux/tracepoint.h>
> >> +#include <linux/kexec.h>
> >>  
> >>  DECLARE_TRACE(kernel_printk,
> >>  TPPROTO(unsigned long retaddr),
> >> @@ -15,5 +16,14 @@ DECLARE_TRACE(kernel_module_free,
> >>  DECLARE_TRACE(kernel_module_load,
> >>  TPPROTO(struct module *mod),
> >>  TPARGS(mod));
> >> +DECLARE_TRACE(kernel_panic,
> >> + TPPROTO(const char *fmt, va_list args),
> >> + TPARGS(fmt, args));
> >> +DECLARE_TRACE(kernel_kernel_kexec,
> >> + TPPROTO(struct kimage *image),
> >> + TPARGS(image));
> >> +DECLARE_TRACE(kernel_crash_kexec,
> >> + TPPROTO(struct kimage *image, struct pt_regs *regs),
> >> + TPARGS(image, regs));
> >>  
> >>  #endif
> >> diff --git a/kernel/kexec.c b/kernel/kexec.c
> >> index aef2653..56cdaac 100644
> >> --- a/kernel/kexec.c
> >> +++ b/kernel/kexec.c
> >> @@ -30,6 +30,7 @@
> >>  #include <linux/pm.h>
> >>  #include <linux/cpu.h>
> >>  #include <linux/console.h>
> >> +#include <trace/kernel.h>
> >>  
> >>  #include <asm/page.h>
> >>  #include <asm/uaccess.h>
> >> @@ -37,6 +38,9 @@
> >>  #include <asm/system.h>
> >>  #include <asm/sections.h>
> >>  
> >> +DEFINE_TRACE(kernel_kernel_kexec);
> >> +DEFINE_TRACE(kernel_crash_kexec);
> >> +
> >>  /* Per cpu memory for storing cpu states in case of system crash. */
> >>  note_buf_t* crash_notes;
> >>  
> >> @@ -1062,6 +1066,8 @@ asmlinkage long compat_sys_kexec_load(unsigned long entry,
> >>  
> >>  void crash_kexec(struct pt_regs *regs)
> >>  {
> >> + trace_kernel_crash_kexec(kexec_crash_image, regs);
> >> +
> >>  /* Take the kexec_mutex here to prevent sys_kexec_load
> >>  * running on one cpu from replacing the crash kernel
> >>  * we are using after a panic on a different cpu.
> >> @@ -1428,6 +1434,8 @@ int kernel_kexec(void)
> >>  {
> >>  int error = 0;
> >>  
> >> + trace_kernel_kernel_kexec(kexec_image);
> >> +
> >>  if (!mutex_trylock(&kexec_mutex))
> >>  return -EBUSY;
> >>  if (!kexec_image) {
> >> diff --git a/kernel/panic.c b/kernel/panic.c
> >> index 12c5a0a..3fa642e 100644
> >> --- a/kernel/panic.c
> >> +++ b/kernel/panic.c
> >> @@ -21,6 +21,9 @@
> >>  #include <linux/debug_locks.h>
> >>  #include <linux/random.h>
> >>  #include <linux/kallsyms.h>
> >> +#include <trace/kernel.h>
> >> +
> >> +DEFINE_TRACE(kernel_panic);
> >>  
> >>  int panic_on_oops;
> >>  int tainted;
> >> @@ -68,6 +71,10 @@ NORET_TYPE void panic(const char * fmt, ...)
> >>  unsigned long caller = (unsigned long) __builtin_return_address(0);
> >>  #endif
> >>  
> >> + va_start(args, fmt);
> >> + trace_kernel_panic(fmt, args);
> >> + va_end(args);
> >> +
> >>  /*
> >>  * It's possible to come here directly from a panic-assertion and not
> >>  * have preempt disabled. Some functions called from here want
> >> -- 
> >> 1.5.5.3
> >> 
> >> 
> >> 
> >> _______________________________________________
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> >> ltt-dev at lists.casi.polymtl.ca
> >> http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev
> >> 
> > 
> > -- 
> > Mathieu Desnoyers
> > OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
> > 
> >
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-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68