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>
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@ -6252,6 +6252,8 @@ SYSCALL_DEFINE5(perf_event_open,
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}
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}
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}
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}
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get_online_cpus();
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event = perf_event_alloc(&attr, cpu, task, group_leader, NULL,
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event = perf_event_alloc(&attr, cpu, task, group_leader, NULL,
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NULL, NULL);
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NULL, NULL);
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if (IS_ERR(event)) {
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if (IS_ERR(event)) {
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@ -6391,6 +6393,8 @@ SYSCALL_DEFINE5(perf_event_open,
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perf_unpin_context(ctx);
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perf_unpin_context(ctx);
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mutex_unlock(&ctx->mutex);
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mutex_unlock(&ctx->mutex);
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put_online_cpus();
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event->owner = current;
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event->owner = current;
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mutex_lock(¤t->perf_event_mutex);
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mutex_lock(¤t->perf_event_mutex);
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@ -6419,6 +6423,7 @@ err_context:
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err_alloc:
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err_alloc:
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free_event(event);
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free_event(event);
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err_task:
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err_task:
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put_online_cpus();
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if (task)
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if (task)
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put_task_struct(task);
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put_task_struct(task);
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err_group_fd:
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err_group_fd:
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