Commit fbfc623f authored Jun 15, 2012 by Yan, Zheng Committed by Ingo Molnar Jun 18, 2012

perf: Avoid race between cpu hotplug and installing event

perf_event_open() requires the cpu on which to install event is online,
but the cpu can go offline after perf_event_open checks that. Add a
get_online_cpus()/put_online_cpus() pair to avoid the race.

Signed-off-by: Zheng Yan <zheng.z.yan@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1339741902-8449-3-git-send-email-zheng.z.yan@intel.com

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

parent 4b4969b1

kernel/events/core.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -6252,6 +6252,8 @@ SYSCALL_DEFINE5(perf_event_open,
		}
		}

		get_online_cpus();

		event = perf_event_alloc(&attr, cpu, task, group_leader, NULL,
		NULL, NULL);
		if (IS_ERR(event)) {
		@@ -6391,6 +6393,8 @@ SYSCALL_DEFINE5(perf_event_open,
		perf_unpin_context(ctx);
		mutex_unlock(&ctx->mutex);

		put_online_cpus();

		event->owner = current;

		mutex_lock(&current->perf_event_mutex);
		@@ -6419,6 +6423,7 @@ SYSCALL_DEFINE5(perf_event_open,
		err_alloc:
		free_event(event);
		err_task:
		put_online_cpus();
		if (task)
		put_task_struct(task);
		err_group_fd: