Messages in this thread Patch in this message |  | | | From | Frederic Weisbecker <> | | Subject | [PATCH 4/5] tracing/events: don't use wake up for events | | Date | Sun, 22 Mar 2009 23:10:46 +0100 |
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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: Ingo Molnar <mingo@elte.hu> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> --- kernel/trace/trace.c | 26 +++++++++++++++++++++----- kernel/trace/trace.h | 2 ++ kernel/trace/trace_events_stage_3.h | 2 +- 3 files changed, 24 insertions(+), 6 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index f0e1337..8dddb42 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -860,15 +860,25 @@ 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, - struct ring_buffer_event *event, - unsigned long flags, int pc) +static inline void __trace_buffer_unlock_commit(struct trace_array *tr, + struct ring_buffer_event *event, + 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); - trace_wake_up(); + + 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 * @@ -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 diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index f267723..54fd9bc 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -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); diff --git a/kernel/trace/trace_events_stage_3.h b/kernel/trace/trace_events_stage_3.h index ebf215e..9a3bd49 100644 --- a/kernel/trace/trace_events_stage_3.h +++ b/kernel/trace/trace_events_stage_3.h @@ -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); \ -- 1.6.1
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