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Commit 8bb39f9a authored by Mike Galbraith's avatar Mike Galbraith Committed by Ingo Molnar
Browse files

perf: Fix 'perf sched record' deadlock 



perf sched record can deadlock a box should the holder of
handle->data->lock take an interrupt, and then attempt to
acquire an rq lock held by a CPU trying to acquire the
same lock. Disable interrupts.

   CPU0                            CPU1
   sched event with rq->lock held
                                   grab handle->data->lock
   spin on handle->data->lock
                                   interrupt
                                   try to grab rq->lock

Reported-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Signed-off-by: default avatarMike Galbraith <efault@gmx.de>
Tested-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1269598293.6174.8.camel@marge.simson.net>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 257ef9d2

kernel/perf_event.c

+12 −3
Original line number Diff line number Diff line
@@ -3376,15 +3376,23 @@ static void perf_event_task_output(struct perf_event *event, 
				     struct perf_task_event *task_event)

{

	struct perf_output_handle handle;

	int size;

	struct task_struct *task = task_event->task;

	int ret;

	unsigned long flags;

	int size, ret;



	/*

	 * If this CPU attempts to acquire an rq lock held by a CPU spinning

	 * in perf_output_lock() from interrupt context, it's game over.

	 */

	local_irq_save(flags);



	size  = task_event->event_id.header.size;

	ret = perf_output_begin(&handle, event, size, 0, 0);



	if (ret)

	if (ret) {

		local_irq_restore(flags);

		return;

	}



	task_event->event_id.pid = perf_event_pid(event, task);

	task_event->event_id.ppid = perf_event_pid(event, current);
@@ -3395,6 +3403,7 @@ static void perf_event_task_output(struct perf_event *event, 
	perf_output_put(&handle, task_event->event_id);



	perf_output_end(&handle);

	local_irq_restore(flags);

}



static int perf_event_task_match(struct perf_event *event)