Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751347Ab0GJRax (ORCPT ); Sat, 10 Jul 2010 13:30:53 -0400 Received: from e31.co.us.ibm.com ([32.97.110.149]:51774 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750736Ab0GJRav (ORCPT ); Sat, 10 Jul 2010 13:30:51 -0400 Message-ID: <4C38AE46.2090803@us.ibm.com> Date: Sat, 10 Jul 2010 10:30:46 -0700 From: Darren Hart User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.10) Gecko/20100528 Thunderbird/3.0.5 MIME-Version: 1.0 To: rostedt@goodmis.org CC: linux-kernel@vger.kernel.org, Thomas Gleixner , Peter Zijlstra , Ingo Molnar , Eric Dumazet , John Kacur , Mike Galbraith , linux-rt-users@vger.kernel.org Subject: Re: [PATCH 2/4 V2] rtmutex: add BUG_ON if a task attempts to block on two locks References: <1278714780-788-1-git-send-email-dvhltc@us.ibm.com> <1278714780-788-3-git-send-email-dvhltc@us.ibm.com> <1278721825.1537.171.camel@gandalf.stny.rr.com> In-Reply-To: <1278721825.1537.171.camel@gandalf.stny.rr.com> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2994 Lines: 83 On 07/09/2010 05:30 PM, Steven Rostedt wrote: > 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. > No objection. >From 31c7b6c5657bcc897ddc79d7f9bb1942eb4c854a Mon Sep 17 00:00:00 2001 From: Darren Hart Date: Fri, 9 Jul 2010 17:46:05 -0400 Subject: [PATCH 2/4] rtmutex: add WARN_ON if a task attempts to block on two locks 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 WARN_ON to catch this scenario early. V2: use a WARN_ON instead of a BUG_ON per Steven's request. 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..5262d0f 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. */ + WARN_ON(task->pi_blocked_on != NULL); + task->pi_blocked_on = waiter; raw_spin_unlock(&task->pi_lock); -- 1.7.0.4 -- 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/