From: lemonlime51@gmail.com (Matthias Bonne)
To: kernelnewbies@lists.kernelnewbies.org
Subject: Question on mutex code
Date: Mon, 16 Mar 2015 05:40:15 +0200 [thread overview]
Message-ID: <5506509F.1040108@gmail.com> (raw)
In-Reply-To: <20150315221018.GA25881@debian>
On 03/16/15 00:10, Rabin Vincent wrote:
> On Sun, Mar 15, 2015 at 11:49:07PM +0200, Matthias Bonne wrote:
>> So the counter is set to 1 before taking the spinlock, which I think
>> might cause the race. Did I miss something?
>
> Yes, you miss the fact that __mutex_slowpath_needs_to_unlock() is 0 for
> the CONFIG_DEBUG_MUTEXES case:
>
> #ifdef CONFIG_DEBUG_MUTEXES
> # include "mutex-debug.h"
> # include <asm-generic/mutex-null.h>
> /*
> * Must be 0 for the debug case so we do not do the unlock outside of the
> * wait_lock region. debug_mutex_unlock() will do the actual unlock in this
> * case.
> */
> # undef __mutex_slowpath_needs_to_unlock
> # define __mutex_slowpath_needs_to_unlock() 0
>
Right, I overlooked this part. Thanks to both of you for the
clarifications.
WARNING: multiple messages have this Message-ID (diff)
From: Matthias Bonne <lemonlime51@gmail.com>
To: Rabin Vincent <rabin@rab.in>
Cc: Davidlohr Bueso <dave@stgolabs.net>,
Yann Droneaud <ydroneaud@opteya.com>,
kernelnewbies@kernelnewbies.org, linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>
Subject: Re: Question on mutex code
Date: Mon, 16 Mar 2015 05:40:15 +0200 [thread overview]
Message-ID: <5506509F.1040108@gmail.com> (raw)
In-Reply-To: <20150315221018.GA25881@debian>
On 03/16/15 00:10, Rabin Vincent wrote:
> On Sun, Mar 15, 2015 at 11:49:07PM +0200, Matthias Bonne wrote:
>> So the counter is set to 1 before taking the spinlock, which I think
>> might cause the race. Did I miss something?
>
> Yes, you miss the fact that __mutex_slowpath_needs_to_unlock() is 0 for
> the CONFIG_DEBUG_MUTEXES case:
>
> #ifdef CONFIG_DEBUG_MUTEXES
> # include "mutex-debug.h"
> # include <asm-generic/mutex-null.h>
> /*
> * Must be 0 for the debug case so we do not do the unlock outside of the
> * wait_lock region. debug_mutex_unlock() will do the actual unlock in this
> * case.
> */
> # undef __mutex_slowpath_needs_to_unlock
> # define __mutex_slowpath_needs_to_unlock() 0
>
Right, I overlooked this part. Thanks to both of you for the
clarifications.
next prev parent reply other threads:[~2015-03-16 3:40 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-04 0:13 Question on mutex code Matthias Bonne
2015-03-10 13:03 ` Yann Droneaud
2015-03-10 13:03 ` Yann Droneaud
2015-03-10 14:59 ` Valdis.Kletnieks at vt.edu
2015-03-10 14:59 ` Valdis.Kletnieks
2015-03-14 23:08 ` Matthias Bonne
2015-03-14 23:08 ` Matthias Bonne
2015-03-14 23:05 ` Matthias Bonne
2015-03-14 23:05 ` Matthias Bonne
2015-03-15 1:03 ` Davidlohr Bueso
2015-03-15 1:04 ` Davidlohr Bueso
2015-03-15 1:09 ` Davidlohr Bueso
2015-03-15 1:10 ` Davidlohr Bueso
2015-03-15 21:49 ` Matthias Bonne
2015-03-15 21:49 ` Matthias Bonne
2015-03-15 22:10 ` Rabin Vincent
2015-03-15 22:11 ` Rabin Vincent
2015-03-16 3:40 ` Matthias Bonne [this message]
2015-03-16 3:40 ` Matthias Bonne
2015-03-15 22:18 ` Davidlohr Bueso
2015-03-15 22:19 ` Davidlohr Bueso
2015-03-15 22:23 ` Davidlohr Bueso
2015-03-15 22:24 ` Davidlohr Bueso
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