From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754112AbZBIUtl (ORCPT ); Mon, 9 Feb 2009 15:49:41 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752202AbZBIUtc (ORCPT ); Mon, 9 Feb 2009 15:49:32 -0500 Received: from e8.ny.us.ibm.com ([32.97.182.138]:33105 "EHLO e8.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751922AbZBIUtb (ORCPT ); Mon, 9 Feb 2009 15:49:31 -0500 Message-ID: <499096D5.9070903@us.ibm.com> Date: Mon, 09 Feb 2009 12:49:25 -0800 From: Darren Hart User-Agent: Thunderbird 2.0.0.19 (X11/20090105) MIME-Version: 1.0 To: Peter Zijlstra CC: "Pallipadi, Venkatesh" , Catalin Marinas , linux-kernel , Andrew Morton , Thomas Gleixner , Ingo Molnar Subject: Re: [PATCH -v2] futex: fix reference leak References: <1234181898.16083.26.camel@pc1117.cambridge.arm.com> <1234190649.16083.44.camel@pc1117.cambridge.arm.com> <1234192363.5951.129.camel@laptop> <1234197950.5951.132.camel@laptop> <1234198023.5951.133.camel@laptop> <1234200538.16083.52.camel@pc1117.cambridge.arm.com> <1234203975.5951.143.camel@laptop> <1234205595.4286.223.camel@localhost.localdomain> <1234205874.5951.151.camel@laptop> In-Reply-To: <1234205874.5951.151.camel@laptop> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra wrote: > On Mon, 2009-02-09 at 10:53 -0800, Pallipadi, Venkatesh wrote: >> Yes. This patch fixes the problem on my system. With git, without the >> patch I see the same oops as before on reboot. With the patch, system >> reboots cleanly. >> OK, I remember why I didn't do this in the set I sent to Ingo for -tip. The unqueue_me() call drops the key ref for us. Eventually I think we should take/release references and locks in the same function as much as possible, but for now I left them where they were. I suspect this patch is actually dropping one extra key ref than it should, but because Caralin has been testing on linux.git and not -tip, the get/put patches I submitted there aren't included, so this patch compensates for one of those missing patches :-) Caralin, can you try applying the following patches from linux-tip without this patch and see if your problem still exists? 42d35d48ce7cefb9429880af19d1c329d1554e7a - futex: make futex_(get|put)_key() calls symmetric 90621c40cc4ab7b0a414311ce37e7cc7173403b6 - futex: catch certain assymetric (get|put)_futex_key calls I haven't tried applying these to linux-2.6.git myself, so they may not apply cleanly. Thanks, Darren Hart >> A minor typo in the patch >> + ret = -RESTART_RESTARTBLOCK; >> should be >> + ret = -ERESTART_RESTARTBLOCK; > > Gah, so much for my copy-paste skillz ;-) > > Thanks! > > --- > Catalin noticed that (38d47c1b7075: futex: rely on > get_user_pages() for shared futexes) caused an mm_struct leak. > > Some tracing with the function graph tracer quickly pointed out that > futex_wait() has exit paths with unbalanced reference counts. > > Signed-off-by: Peter Zijlstra > Tested-by: "Pallipadi, Venkatesh" > --- > kernel/futex.c | 23 +++++++++++++++-------- > 1 files changed, 15 insertions(+), 8 deletions(-) > > diff --git a/kernel/futex.c b/kernel/futex.c > index f89d373..ff06c76 100644 > --- a/kernel/futex.c > +++ b/kernel/futex.c > @@ -1284,18 +1284,23 @@ retry: > */ > > /* If we were woken (and unqueued), we succeeded, whatever. */ > - if (!unqueue_me(&q)) > - return 0; > - if (rem) > - return -ETIMEDOUT; > + if (!unqueue_me(&q)) { > + ret = 0; > + goto out_put_key; > + } > + if (rem) { > + ret = -ETIMEDOUT; > + goto out_put_key; > + } > > /* > * We expect signal_pending(current), but another thread may > * have handled it for us already. > */ > - if (!abs_time) > - return -ERESTARTSYS; > - else { > + if (!abs_time) { > + ret = -ERESTARTSYS; > + goto out_put_key; > + } else { > struct restart_block *restart; > restart = ¤t_thread_info()->restart_block; > restart->fn = futex_wait_restart; > @@ -1309,11 +1314,13 @@ retry: > restart->futex.flags |= FLAGS_SHARED; > if (clockrt) > restart->futex.flags |= FLAGS_CLOCKRT; > - return -ERESTART_RESTARTBLOCK; > + ret = -ERESTART_RESTARTBLOCK; > + goto out_put_key; > } > > out_unlock_put_key: > queue_unlock(&q, hb); > +out_put_key: > put_futex_key(fshared, &q.key); > > out: > > -- Darren Hart IBM Linux Technology Center Real-Time Linux Team