Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751090AbVLTPdv (ORCPT ); Tue, 20 Dec 2005 10:33:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751095AbVLTPdv (ORCPT ); Tue, 20 Dec 2005 10:33:51 -0500 Received: from e36.co.us.ibm.com ([32.97.110.154]:25286 "EHLO e36.co.us.ibm.com") by vger.kernel.org with ESMTP id S1751090AbVLTPdu (ORCPT ); Tue, 20 Dec 2005 10:33:50 -0500 Date: Tue, 20 Dec 2005 21:20:04 +0530 From: Dinakar Guniguntala To: Ingo Molnar Cc: David Singleton , linux-kernel@vger.kernel.org, robustmutexes@lists.osdl.org Subject: Re: Recursion bug in -rt Message-ID: <20051220155004.GA3906@in.ibm.com> Reply-To: dino@in.ibm.com References: <20051214223912.GA4716@in.ibm.com> <43A1BD61.5070409@mvista.com> <20051220131956.GA24408@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20051220131956.GA24408@elte.hu> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 909 Lines: 25 On Tue, Dec 20, 2005 at 02:19:56PM +0100, Ingo Molnar wrote: > > hm, i'm looking at -rf4 - these changes look fishy: > > - _raw_spin_lock(&lock_owner(lock)->task->pi_lock); > + if (current != lock_owner(lock)->task) > + _raw_spin_lock(&lock_owner(lock)->task->pi_lock); > > why is this done? > Ingo, this is to prevent a kernel hang due to application error. Basically when an application does a pthread_mutex_lock twice on a _nonrecursive_ mutex with robust/PI attributes the whole system hangs. Ofcourse the application clearly should not be doing anything like that, but it should not end up hanging the system either -Dinakar - 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/