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

[Mathieu Desnoyers]

* Zhaolei (zhaolei at cn.fujitsu.com) wrote:
> * From: "Mathieu Desnoyers" <mathieu.desnoyers at polymtl.ca>
> >* 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?
> >> 
> > 
> > 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?
> 

Yes,

it's possible that it directly applies, can you confirm and resend ?

Thanks,

Mathieu

> 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
> > 
> >
> _______________________________________________
> 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