perf: Ensure we call add_event_to_ctx() with the right locks held

Even though we call it from the inherit path, where the child is
not yet accessible, we need to hold ctx->lock, add_event_to_ctx()
assumes IRQs are disabled.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index eaf1c5d..f395fb4 100644 (file)
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -5913,6 +5913,7 @@ inherit_event(struct perf_event *parent_event,
              struct perf_event_context *child_ctx)
 {
        struct perf_event *child_event;
+       unsigned long flags;
 
        /*
         * Instead of creating recursive hierarchies of events,
@@ -5957,7 +5958,9 @@ inherit_event(struct perf_event *parent_event,
        /*
         * Link it up in the child's context:
         */
+       raw_spin_lock_irqsave(&child_ctx->lock, flags);
        add_event_to_ctx(child_event, child_ctx);
+       raw_spin_unlock_irqrestore(&child_ctx->lock, flags);
 
        /*
         * Get a reference to the parent filp - we will fput it