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    Subject[tip:perf/urgent] perf: Fix tear-down of inherited group events
    Commit-ID:  38b435b16c36b0d863efcf3f07b34a6fac9873fd
    Gitweb: http://git.kernel.org/tip/38b435b16c36b0d863efcf3f07b34a6fac9873fd
    Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
    AuthorDate: Tue, 15 Mar 2011 14:37:10 +0100
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Wed, 16 Mar 2011 14:04:14 +0100

    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>
    ---
    kernel/perf_event.c | 13 ++++++++-----
    1 files changed, 8 insertions(+), 5 deletions(-)

    diff --git a/kernel/perf_event.c b/kernel/perf_event.c
    index 533f715..3472bb1 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);
    }

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