Commit fed66e2c authored Jun 11, 2015 by Peter Zijlstra Committed by Ingo Molnar Aug 04, 2015

perf: Fix fasync handling on inherited events



Vince reported that the fasync signal stuff doesn't work proper for
inherited events. So fix that.

Installing fasync allocates memory and sets filp->f_flags |= FASYNC,
which upon the demise of the file descriptor ensures the allocation is
freed and state is updated.

Now for perf, we can have the events stick around for a while after the
original FD is dead because of references from child events. So we
cannot copy the fasync pointer around. We can however consistently use
the parent's fasync, as that will be updated.

Reported-and-Tested-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Cc: Arnaldo Carvalho deMelo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: eranian@google.com
Link: http://lkml.kernel.org/r/1434011521.1495.71.camel@twins


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 5542b2aa

kernel/events/core.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -4740,12 +4740,20 @@ static const struct file_operations perf_fops = {
		* to user-space before waking everybody up.
		*/

		static inline struct fasync_struct *perf_event_fasync(struct perf_event event)
		{
		/* only the parent has fasync state */
		if (event->parent)
		event = event->parent;
		return &event->fasync;
		}

		void perf_event_wakeup(struct perf_event *event)
		{
		ring_buffer_wakeup(event);

		if (event->pending_kill) {
		kill_fasync(&event->fasync, SIGIO, event->pending_kill);
		kill_fasync(perf_event_fasync(event), SIGIO, event->pending_kill);
		event->pending_kill = 0;
		}
		}
		@@ -6124,7 +6132,7 @@ static int __perf_event_overflow(struct perf_event *event,
		else
		perf_event_output(event, data, regs);

		if (event->fasync && event->pending_kill) {
		if (*perf_event_fasync(event) && event->pending_kill) {
		event->pending_wakeup = 1;
		irq_work_queue(&event->pending);
		}

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