Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756960AbZCLPPw (ORCPT ); Thu, 12 Mar 2009 11:15:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755668AbZCLPPn (ORCPT ); Thu, 12 Mar 2009 11:15:43 -0400 Received: from e4.ny.us.ibm.com ([32.97.182.144]:40052 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755624AbZCLPPn (ORCPT ); Thu, 12 Mar 2009 11:15:43 -0400 Message-ID: <49B9271A.8040502@us.ibm.com> Date: Thu, 12 Mar 2009 08:15:38 -0700 From: Darren Hart User-Agent: Thunderbird 2.0.0.19 (X11/20090105) MIME-Version: 1.0 To: Peter Zijlstra CC: Thomas Gleixner , linux-kernel@vger.kernel.org, Ingo Molnar , Rusty Russell Subject: Re: [PATCH 5/6] futex: unlock before returning -EFAULT References: <20090312075349.9856.83687.stgit@Aeon> <20090312075606.9856.88729.stgit@Aeon> <1236852816.5090.117.camel@laptop> <1236856017.5090.235.camel@laptop> In-Reply-To: <1236856017.5090.235.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 Content-Length: 1486 Lines: 39 Peter Zijlstra wrote: > On Thu, 2009-03-12 at 11:47 +0100, Thomas Gleixner wrote: >> On Thu, 12 Mar 2009, Peter Zijlstra wrote: >> >>> On Thu, 2009-03-12 at 00:56 -0700, Darren Hart wrote: >>>> futex_lock_pi can potentially return -EFAULT with the rt_mutex held. This >>>> seems like the wrong thing to do as userspace should assume -EFAULT means the >>>> lock was not taken. Even if it could figure this out, we'd be leaving the >>>> pi_state->owner in an inconsistent state. This patch unlocks the rt_mutex >>>> prior to returning -EFAULT to userspace. >>> lockdep would complain, one is not to leave the kernel with locks held. >> That would break pi futexes in bits and pieces. >> >> T1 takes F1 >> T2 blocks on F1 >> -> T2 sets up rt_mutex and locks it for T1 >> T2 blocks on rt_mutex and boosts T1 >> >> T1 calls a non futex syscall >> T1 returns from syscall with the rt_mutex still locked >> >> Thanks, > > Oh right, raw rt_mutex stuff isn't lockdep annotated, and you use the > robust futex infrastructure to ensure stuff gets unlocked when holder > dies. That should work out. > OK, are there any other concerns with this patch? -- Darren Hart IBM Linux Technology Center Real-Time Linux Team -- 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/