Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757863AbXI3PyJ (ORCPT ); Sun, 30 Sep 2007 11:54:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758307AbXI3Pxt (ORCPT ); Sun, 30 Sep 2007 11:53:49 -0400 Received: from www.tglx.de ([62.245.132.106]:37721 "EHLO www.tglx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757994AbXI3Pxs (ORCPT ); Sun, 30 Sep 2007 11:53:48 -0400 Date: Sun, 30 Sep 2007 17:53:24 +0200 (CEST) From: Thomas Gleixner To: Ingo Molnar cc: Martin Schwidefsky , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Ulrich Drepper , Linus Torvalds Subject: Re: [PATCH] robust futex thread exit race In-Reply-To: <20070930151827.GB23127@elte.hu> Message-ID: References: <1191164539.4047.5.camel@localhost> <20070930151827.GB23127@elte.hu> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1475 Lines: 36 On Sun, 30 Sep 2007, Ingo Molnar wrote: > * Martin Schwidefsky wrote: > > > Hi Ingo, > > I finally found the bug that causes tst-robust8 from the glibc to fail > > on s390x. Turned out to be a common code problem with the processing of > > the robust futex list. The patch below fixes the bug for me. > > good catch! A quick preliminary review of your patch indicates it's fine > - and it might be v2.6.23 material. > > Acked-by: Ingo Molnar Acked-by: Thomas Gleixner > > Calling handle_futex_death in exit_robust_list for the different > > robust mutexes of a thread basically frees the mutex. Another thread > > might grab the lock immediately which updates the next pointer of the > > mutex. fetch_robust_entry over the next pointer might therefore branch > > into the robust mutex list of a different thread. This can cause two > > problems: 1) some mutexes held by the dead thread are not getting > > freed and 2) some mutexs held by a different thread are freed. The > > next point need to be read before calling handle_futex_death. > > nasty race... Ulrich, Thomas, do you concur? Yes. Where do they sell those brown paperbags again ? tglx - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/