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    Subject[PATCH] perf: Fix tear-down of inherited group events
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    Subject: perf: Fix tear-down of inherited group events
    From: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Date: Tue Mar 15 14:37:10 CET 2011

    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-by: Vince Weaver <vweaver1@eecs.utk.edu>
    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: stable@kernel.org # .35+
    ---
    kernel/perf_event.c | 13 ++++++++-----
    1 file changed, 8 insertions(+), 5 deletions(-)

    Index: linux-2.6/kernel/perf_event.c
    ===================================================================
    --- linux-2.6.orig/kernel/perf_event.c
    +++ linux-2.6/kernel/perf_event.c
    @@ -6722,17 +6722,20 @@ __perf_event_exit_task(struct perf_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);
    }


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