Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753461Ab2HMIPY (ORCPT ); Mon, 13 Aug 2012 04:15:24 -0400 Received: from merlin.infradead.org ([205.233.59.134]:49643 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752967Ab2HMIPW convert rfc822-to-8bit (ORCPT ); Mon, 13 Aug 2012 04:15:22 -0400 Message-ID: <1344845704.31459.11.camel@twins> Subject: Re: RFC: mutex: hung tasks on SMP platforms with asm-generic/mutex-xchg.h From: Peter Zijlstra To: Nicolas Pitre Cc: Will Deacon , "linux-kernel@vger.kernel.org" , Ingo Molnar , Thomas Gleixner , Chris Mason , Arnd Bergmann , "linux-arm-kernel@lists.infradead.org" Date: Mon, 13 Aug 2012 10:15:04 +0200 In-Reply-To: References: <20120807115647.GA12828@mudshark.cambridge.arm.com> <20120809144953.GC18486@mudshark.cambridge.arm.com> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1077 Lines: 28 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? -- 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/