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Commit 07edf712 authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar
Browse files

tracing/events: don't use wake up for events 



Impact: fix hard-lockup with sched switch events

Some ftrace events, such as sched wakeup, can be traced
while the runqueue lock is hold. Since they are using
trace_current_buffer_unlock_commit(), they call wake_up()
which can try to grab the runqueue lock too, resulting in
a deadlock.

Now for all event, we call a new helper:
trace_nowake_buffer_unlock_commit() which do pretty the same than
trace_current_buffer_unlock_commit() except than it doesn't call
trace_wake_up().

Reported-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1237759847-21025-4-git-send-email-fweisbec@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 9bd7d099

kernel/trace/trace.c

+21 −5
Original line number Diff line number Diff line
@@ -860,17 +860,27 @@ static void ftrace_trace_stack(struct trace_array *tr, 
static void ftrace_trace_userstack(struct trace_array *tr,

				   unsigned long flags, int pc);



void trace_buffer_unlock_commit(struct trace_array *tr,

static inline void __trace_buffer_unlock_commit(struct trace_array *tr,

					struct ring_buffer_event *event,

				unsigned long flags, int pc)

					unsigned long flags, int pc,

					int wake)

{

	ring_buffer_unlock_commit(tr->buffer, event);



	ftrace_trace_stack(tr, flags, 6, pc);

	ftrace_trace_userstack(tr, flags, pc);



	if (wake)

		trace_wake_up();

}



void trace_buffer_unlock_commit(struct trace_array *tr,

					struct ring_buffer_event *event,

					unsigned long flags, int pc)

{

	__trace_buffer_unlock_commit(tr, event, flags, pc, 1);

}



struct ring_buffer_event *

trace_current_buffer_lock_reserve(unsigned char type, unsigned long len,

				  unsigned long flags, int pc)
@@ -882,7 +892,13 @@ trace_current_buffer_lock_reserve(unsigned char type, unsigned long len, 
void trace_current_buffer_unlock_commit(struct ring_buffer_event *event,

					unsigned long flags, int pc)

{

	return trace_buffer_unlock_commit(&global_trace, event, flags, pc);

	return __trace_buffer_unlock_commit(&global_trace, event, flags, pc, 1);

}



void trace_nowake_buffer_unlock_commit(struct ring_buffer_event *event,

					unsigned long flags, int pc)

{

	return __trace_buffer_unlock_commit(&global_trace, event, flags, pc, 0);

}



void

kernel/trace/trace.h

+2 −0
Original line number Diff line number Diff line
@@ -483,6 +483,8 @@ trace_current_buffer_lock_reserve(unsigned char type, unsigned long len, 
				  unsigned long flags, int pc);

void trace_current_buffer_unlock_commit(struct ring_buffer_event *event,

					unsigned long flags, int pc);

void trace_nowake_buffer_unlock_commit(struct ring_buffer_event *event,

					unsigned long flags, int pc);



struct trace_entry *tracing_get_trace_entry(struct trace_array *tr,

						struct trace_array_cpu *data);

kernel/trace/trace_events_stage_3.h

+1 −1
Original line number Diff line number Diff line
@@ -222,7 +222,7 @@ static void ftrace_raw_event_##call(proto) \ 
									\

	assign;								\

									\

	trace_current_buffer_unlock_commit(event, irq_flags, pc);	\

	trace_nowake_buffer_unlock_commit(event, irq_flags, pc);	\

									\

	if (call->preds && !filter_match_preds(call, entry))		\

		ring_buffer_event_discard(event);			\