Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755950Ab0GJAa3 (ORCPT ); Fri, 9 Jul 2010 20:30:29 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:58471 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752439Ab0GJAa1 (ORCPT ); Fri, 9 Jul 2010 20:30:27 -0400 X-Authority-Analysis: v=1.1 cv=iR3a2x+wy8z+UqYHl7KFtKHYySPA0Tf/DXXAzrkvAHo= c=1 sm=0 a=-TRnPmo8vm0A:10 a=uEzv4HemXiYA:10 a=7U3hwN5JcxgA:10 a=Q9fys5e9bTEA:10 a=gMqfjgEr1zLu/65IO0LwxA==:17 a=VnNF1IyMAAAA:8 a=JfrnYn6hAAAA:8 a=pGLkceISAAAA:8 a=20KFwNOVAAAA:8 a=meVymXHHAAAA:8 a=YyMF1Dys4DWpe-2ipnwA:9 a=8UJDUG-lhAAGm64wQk8A:7 a=bxsN-4n8S6T-tnypjBaJfIr2aBsA:4 a=PUjeQqilurYA:10 a=Zh68SRI7RUMA:10 a=3Rfx1nUSh_UA:10 a=MSl-tDqOz04A:10 a=jEp0ucaQiEUA:10 a=jeBq3FmKZ4MA:10 a=_RhRFcbxBZMA:10 a=gMqfjgEr1zLu/65IO0LwxA==:117 X-Cloudmark-Score: 0 X-Originating-IP: 74.67.89.75 Subject: Re: [PATCH 2/4] rtmutex: add BUG_ON if a task attempts to block on two locks From: Steven Rostedt Reply-To: rostedt@goodmis.org To: Darren Hart Cc: linux-kernel@vger.kernel.org, Thomas Gleixner , Peter Zijlstra , Ingo Molnar , Eric Dumazet , John Kacur , Mike Galbraith , linux-rt-users@vger.kernel.org In-Reply-To: <1278714780-788-3-git-send-email-dvhltc@us.ibm.com> References: <1278714780-788-1-git-send-email-dvhltc@us.ibm.com> <1278714780-788-3-git-send-email-dvhltc@us.ibm.com> Content-Type: text/plain; charset="ISO-8859-15" Organization: Kihon Technologies Inc. Date: Fri, 09 Jul 2010 20:30:25 -0400 Message-ID: <1278721825.1537.171.camel@gandalf.stny.rr.com> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1580 Lines: 45 On Fri, 2010-07-09 at 15:32 -0700, Darren Hart wrote: > rtmutex proxy locking complicates the logic a bit and opens up > the possibility for a task to wake and attempt to take another > sleeping lock without knowing it has been enqueued on another > lock already. Add a BUG_ON to catch this scenario early. > > Signed-off-by: Darren Hart > Cc: Thomas Gleixner > Cc: Peter Zijlstra > Cc: Ingo Molnar > Cc: Eric Dumazet > Cc: John Kacur > Cc: Steven Rostedt > Cc: Mike Galbraith > --- > kernel/rtmutex.c | 3 +++ > 1 files changed, 3 insertions(+), 0 deletions(-) > > diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c > index baac7d9..22f9d18 100644 > --- a/kernel/rtmutex.c > +++ b/kernel/rtmutex.c > @@ -459,6 +459,9 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock, > top_waiter = rt_mutex_top_waiter(lock); > plist_add(&waiter->list_entry, &lock->wait_list); > > + /* Tasks can only block on one lock at a time. */ > + BUG_ON(task->pi_blocked_on != NULL); WARN_ON may be better. Since it may not cause a system crash or other huge bug if it is not true. -- Steve > + > task->pi_blocked_on = waiter; > > raw_spin_unlock(&task->pi_lock); -- 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/