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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 /kernel/trace/trace.c | |
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 'kernel/trace/trace.c')
-rw-r--r-- | kernel/trace/trace.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 88bd9ae..f531301 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -1151,6 +1151,22 @@ void __trace_stack(struct trace_array *tr, unsigned long flags, int skip, __ftrace_trace_stack(tr->buffer, flags, skip, pc); } +/** + * trace_dump_stack - record a stack back trace in the trace buffer + */ +void trace_dump_stack(void) +{ + unsigned long flags; + + if (tracing_disabled || tracing_selftest_running) + return 0; + + local_save_flags(flags); + + /* skipping 3 traces, seems to get us at the caller of this function */ + __ftrace_trace_stack(global_trace.buffer, flags, 3, preempt_count()); +} + void ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags, int pc) { |