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From: Will Deacon <will.deacon@arm.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Nicolas Pitre <nico@fluxnic.net>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
	Chris Mason <chris.mason@fusionio.com>,
	Arnd Bergmann <arnd@arndb.de>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: RFC: mutex: hung tasks on SMP platforms with asm-generic/mutex-xchg.h
Date: Mon, 13 Aug 2012 10:13:49 +0100	[thread overview]
Message-ID: <20120813091349.GA19113@mudshark.cambridge.arm.com> (raw)
In-Reply-To: <1344845704.31459.11.camel@twins>

Hi Peter,

On Mon, Aug 13, 2012 at 09:15:04AM +0100, Peter Zijlstra wrote:
> On Thu, 2012-08-09 at 12:57 -0400, Nicolas Pitre wrote:
> > 
> > In other words, I think this should look like this:
> > 
> > diff --git a/include/asm-generic/mutex-xchg.h b/include/asm-generic/mutex-xchg.h
> > index 580a6d35c7..44a66c99c8 100644
> > --- a/include/asm-generic/mutex-xchg.h
> > +++ b/include/asm-generic/mutex-xchg.h
> > @@ -25,8 +25,11 @@
> >  static inline void
> >  __mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
> >  {
> > -       if (unlikely(atomic_xchg(count, 0) != 1))
> > -               fail_fn(count);
> > +       if (unlikely(atomic_xchg(count, 0) != 1)) {
> > +               /* Mark lock contention explicitly */
> > +               if (likely(atomic_xchg(count, -1) != 1))
> > +                       fail_fn(count);
> > +       }
> >  } 
> 
> OK, I like this.. Thanks guys! Will will you send a final and complete
> patch?

I sent one out on Friday but somehow managed to drop you from CC -- sorry
about that:

  http://thread.gmane.org/gmane.linux.kernel/1341305

Cheers,

Will

  reply	other threads:[~2012-08-13  9:14 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-08-07 11:56 Will Deacon
2012-08-07 13:48 ` Peter Zijlstra
2012-08-07 14:04   ` Will Deacon
2012-08-07 17:14 ` Nicolas Pitre
2012-08-07 17:33   ` Will Deacon
2012-08-07 17:38     ` Will Deacon
2012-08-07 18:28     ` Nicolas Pitre
2012-08-09  5:12 ` Nicolas Pitre
2012-08-09 14:49   ` Will Deacon
2012-08-09 16:17     ` Nicolas Pitre
2012-08-09 16:57       ` Nicolas Pitre
2012-08-09 17:50         ` Will Deacon
2012-08-09 18:09           ` Nicolas Pitre
2012-08-09 18:17             ` Will Deacon
2012-08-09 20:05               ` Nicolas Pitre
2012-08-13  8:15         ` Peter Zijlstra
2012-08-13  9:13           ` Will Deacon [this message]
2012-08-13 13:35           ` Nicolas Pitre
2012-08-13 14:05             ` Peter Zijlstra
2012-08-13 14:11               ` Will Deacon
2012-08-13 14:45                 ` Peter Zijlstra

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