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    Subject[PATCH] perf: Fix perf_event_for_each() to use sibling
    Date
    In perf_event_for_each() we call a function on an event, and then
    iterate over the siblings of the event.

    However we don't call the function on the siblings, we call it
    repeatedly on the original event - it seems "obvious" that we should
    be calling it with sibling as the argument.

    It looks like this broke in commit 75f937f24bd9 ("Fix ctx->mutex
    vs counter->mutex inversion").

    The only effect of the bug is that the PERF_IOC_FLAG_GROUP parameter
    to the ioctls doesn't work.

    Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
    ---

    This one seems so simple that I keep thinking I've missed something,
    I'm sure someone will tell me if I have ;)

    AFAICS tools/perf never exercises this, ie. it always individually
    enables counters - which might explain how it could be broken and
    no one has noticed.
    ---
    kernel/events/core.c | 2 +-
    1 files changed, 1 insertions(+), 1 deletions(-)

    diff --git a/kernel/events/core.c b/kernel/events/core.c
    index 1b5c081..b82121b 100644
    --- a/kernel/events/core.c
    +++ b/kernel/events/core.c
    @@ -3097,7 +3097,7 @@ static void perf_event_for_each(struct perf_event *event,
    perf_event_for_each_child(event, func);
    func(event);
    list_for_each_entry(sibling, &event->sibling_list, group_entry)
    - perf_event_for_each_child(event, func);
    + perf_event_for_each_child(sibling, func);
    mutex_unlock(&ctx->mutex);
    }

    --
    1.7.5.4


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