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

[zhaolei@cn.fujitsu.com (Zhaolei)]

* From: "Mathieu Desnoyers" <mathieu.desnoyers@polymtl.ca>
>* Zhaolei (zhaolei at cn.fujitsu.com) wrote:
>> * From: "Mathieu Desnoyers" <compudj@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?
>> 
> 
> Hi Zhaolei,
> 
> I think having the tracepoints for panic and kexec would be a good
> start. 
Hello, Mathieu

Glad to hear that.

> Then whenever we need more specific hooks to send the data out
> (for crash data extraction), we can add notification hooks at that time.
> Do you have an updated version of panic+kexec instrumentation ?
Do you means update this patch to top of lttng-git-tree only?

B.R.
Zhaolei

> 
> Thanks,
> 
> 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
>> >> 
>> >> 
>> >> 
>> >> _______________________________________________
>> >> ltt-dev mailing list
>> >> 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
>> > 
>> >
>> 
> 
> -- 
> Mathieu Desnoyers
> OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
> 
>