linux-kernel - Re: [PATCH] perf: fix put

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Date:	Fri, 13 Mar 2015 12:53:27 +0800
From:	Leon Yu <chianglungyu@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	Leon Yu <chianglungyu@...il.com>, linux-kernel@...r.kernel.org,
	robert@...ecki.net
Subject: Re: [PATCH] perf: fix put_event() ctx leak

On Thu, Feb 26, 2015 at 8:43 PM, Leon Yu <chianglungyu@...il.com> wrote:
>
> Commit a83fe28e2e45 ("perf: Fix put_event() ctx lock") changed lock logic in
> put_event() by replacing mutex_lock_nested() with perf_event_ctx_lock_nested(),
> but didn't fix subsequent mutex_unlock() with correct counterpart,
> perf_event_ctx_unlock(). ctx is thus leaked as a result of incremented
> refcount in perf_event_ctx_lock_nested().
>
> Signed-off-by: Leon Yu <chianglungyu@...il.com>
> Fixes: a83fe28e2e45 ("perf: Fix put_event() ctx lock")
> ---
>  kernel/events/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index f04daab..453ef61 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -3591,7 +3591,7 @@ static void put_event(struct perf_event *event)
>         ctx = perf_event_ctx_lock_nested(event, SINGLE_DEPTH_NESTING);
>         WARN_ON_ONCE(ctx->parent_ctx);
>         perf_remove_from_context(event, true);
> -       mutex_unlock(&ctx->mutex);
> +       perf_event_ctx_unlock(event, ctx);
>
>         _free_event(event);
>  }

Gentle ping.

It has been two weeks since previous post, the issue remains un-fixed
and affects some more users [1].
It would be very appreciated if I can get some responses from related
maintainers since we're almost
half way to release.

[1] http://marc.info/?l=linux-kernel&m=142618052120848&w=2

-Leon
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