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authorSteven Rostedt <srostedt@redhat.com>2009-12-11 09:48:22 -0500
committerSteven Rostedt <rostedt@goodmis.org>2009-12-11 10:38:47 -0500
commit03889384cee7a198a79447c1ea6aca2c8e54d155 (patch)
tree66794ab12e3196c4bee4d8d020f451e8cc8a1f6d /include
parentdd7f59435782a02ceb6d16b9ce823dd3345d75ec (diff)
downloadop-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.h2
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
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