From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: Re: [PATCH v9 05/19] qspinlock: Optimize for smaller NR_CPUS Date: Thu, 17 Apr 2014 17:49:02 -0400 Message-ID: <53504C4E.8060800@hp.com> References: <1397747051-15401-1-git-send-email-Waiman.Long@hp.com> <1397747051-15401-6-git-send-email-Waiman.Long@hp.com> <20140417155844.GS11096@twins.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140417155844.GS11096@twins.programming.kicks-ass.net> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Peter Zijlstra Cc: linux-arch@vger.kernel.org, Rik van Riel , Raghavendra K T , Gleb Natapov , kvm@vger.kernel.org, Konrad Rzeszutek Wilk , Scott J Norton , x86@kernel.org, Paolo Bonzini , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Ingo Molnar , Chegu Vinod , David Vrabel , "H. Peter Anvin" , xen-devel@lists.xenproject.org, Thomas Gleixner , "Paul E. McKenney" , Linus Torvalds , Oleg Nesterov List-Id: linux-arch.vger.kernel.org On 04/17/2014 11:58 AM, Peter Zijlstra wrote: > On Thu, Apr 17, 2014 at 11:03:57AM -0400, Waiman Long wrote: >> +static __always_inline void >> +clear_pending_set_locked(struct qspinlock *lock, u32 val) >> +{ >> + struct __qspinlock *l = (void *)lock; >> + >> + ACCESS_ONCE(l->locked_pending) = 1; >> +} >> @@ -157,8 +251,13 @@ static inline int trylock_pending(struct qspinlock *lock, u32 *pval) >> * we're pending, wait for the owner to go away. >> * >> * *,1,1 -> *,1,0 >> + * >> + * this wait loop must be a load-acquire such that we match the >> + * store-release that clears the locked bit and create lock >> + * sequentiality; this because not all try_clear_pending_set_locked() >> + * implementations imply full barriers. > You renamed the function referred in the above comment. > Sorry, will fix the comments. -Longman From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from g4t3425.houston.hp.com ([15.201.208.53]:36563 "EHLO g4t3425.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751620AbaDQVtI (ORCPT ); Thu, 17 Apr 2014 17:49:08 -0400 Message-ID: <53504C4E.8060800@hp.com> Date: Thu, 17 Apr 2014 17:49:02 -0400 From: Waiman Long MIME-Version: 1.0 Subject: Re: [PATCH v9 05/19] qspinlock: Optimize for smaller NR_CPUS References: <1397747051-15401-1-git-send-email-Waiman.Long@hp.com> <1397747051-15401-6-git-send-email-Waiman.Long@hp.com> <20140417155844.GS11096@twins.programming.kicks-ass.net> In-Reply-To: <20140417155844.GS11096@twins.programming.kicks-ass.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Peter Zijlstra Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , linux-arch@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, Paolo Bonzini , Konrad Rzeszutek Wilk , "Paul E. McKenney" , Rik van Riel , Linus Torvalds , Raghavendra K T , David Vrabel , Oleg Nesterov , Gleb Natapov , Scott J Norton , Chegu Vinod Message-ID: <20140417214902.sCvvsvUuSm1o9Dvib8wwaWWUrAtcBW7DbjGs_QXHbYo@z> On 04/17/2014 11:58 AM, Peter Zijlstra wrote: > On Thu, Apr 17, 2014 at 11:03:57AM -0400, Waiman Long wrote: >> +static __always_inline void >> +clear_pending_set_locked(struct qspinlock *lock, u32 val) >> +{ >> + struct __qspinlock *l = (void *)lock; >> + >> + ACCESS_ONCE(l->locked_pending) = 1; >> +} >> @@ -157,8 +251,13 @@ static inline int trylock_pending(struct qspinlock *lock, u32 *pval) >> * we're pending, wait for the owner to go away. >> * >> * *,1,1 -> *,1,0 >> + * >> + * this wait loop must be a load-acquire such that we match the >> + * store-release that clears the locked bit and create lock >> + * sequentiality; this because not all try_clear_pending_set_locked() >> + * implementations imply full barriers. > You renamed the function referred in the above comment. > Sorry, will fix the comments. -Longman