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author | Steven Rostedt <srostedt@redhat.com> | 2009-12-11 09:48:22 -0500 |
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committer | Steven Rostedt <rostedt@goodmis.org> | 2009-12-11 10:38:47 -0500 |
commit | 03889384cee7a198a79447c1ea6aca2c8e54d155 (patch) | |
tree | 66794ab12e3196c4bee4d8d020f451e8cc8a1f6d /include | |
parent | dd7f59435782a02ceb6d16b9ce823dd3345d75ec (diff) | |
download | op-kernel-dev-03889384cee7a198a79447c1ea6aca2c8e54d155.zip op-kernel-dev-03889384cee7a198a79447c1ea6aca2c8e54d155.tar.gz |
tracing: Add trace_dump_stack()
I've been asked a few times about how to find out what is calling
some location in the kernel. One way is to use dynamic function tracing
and implement the func_stack_trace. But this only finds out who is
calling a particular function. It does not tell you who is calling
that function and entering a specific if conditional.
I have myself implemented a quick version of trace_dump_stack() for
this purpose a few times, and just needed it now. This is when I realized
that this would be a good tool to have in the kernel like trace_printk().
Using trace_dump_stack() is similar to dump_stack() except that it
writes to the trace buffer instead and can be used in critical locations.
For example:
@@ -5485,8 +5485,12 @@ need_resched_nonpreemptible:
if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
if (unlikely(signal_pending_state(prev->state, prev)))
prev->state = TASK_RUNNING;
- else
+ else {
deactivate_task(rq, prev, 1);
+ trace_printk("Deactivating task %s:%d\n",
+ prev->comm, prev->pid);
+ trace_dump_stack();
+ }
switch_count = &prev->nvcsw;
}
Produces:
<...>-3249 [001] 296.105269: schedule: Deactivating task ntpd:3249
<...>-3249 [001] 296.105270: <stack trace>
=> schedule
=> schedule_hrtimeout_range
=> poll_schedule_timeout
=> do_select
=> core_sys_select
=> sys_select
=> system_call_fastpath
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'include')
-rw-r--r-- | include/linux/kernel.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 3fa4c59..5ad4199 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -492,6 +492,8 @@ extern int __trace_printk(unsigned long ip, const char *fmt, ...) __attribute__ ((format (printf, 2, 3))); +extern void trace_dump_stack(void); + /* * The double __builtin_constant_p is because gcc will give us an error * if we try to allocate the static variable to fmt if it is not a |