perf: Fix tear-down of inherited group events

When destroying inherited events, we need to destroy groups too,
otherwise the event iteration in perf_event_exit_task_context() will
miss group siblings and we leak events with all the consequences.

Reported-and-tested-by: Vince Weaver <vweaver1@eecs.utk.edu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <stable@kernel.org> # .35+
LKML-Reference: <1300196470.2203.61.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 8 insertions, 5 deletions

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 533f71570736..3472bb1a070c 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -6722,17 +6722,20 @@ __perf_event_exit_task(struct perf_event *child_event,
                          struct perf_event_context *child_ctx,
                          struct task_struct *child)
 {
-        struct perf_event *parent_event;
+        if (child_event->parent) {
+                raw_spin_lock_irq(&child_ctx->lock);
+                perf_group_detach(child_event);
+                raw_spin_unlock_irq(&child_ctx->lock);
+        }
 
         perf_remove_from_context(child_event);
 
-        parent_event = child_event->parent;
         /*
-         * It can happen that parent exits first, and has events
+         * It can happen that the parent exits first, and has events
          * that are still around due to the child reference. These
-         * events need to be zapped - but otherwise linger.
+         * events need to be zapped.
          */
-        if (parent_event) {
+        if (child_event->parent) {
                 sync_child_event(child_event, child);
                 free_event(child_event);
         }