Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964926Ab3DPO0h (ORCPT ); Tue, 16 Apr 2013 10:26:37 -0400 Received: from g4t0017.houston.hp.com ([15.201.24.20]:30979 "EHLO g4t0017.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933715Ab3DPO0f (ORCPT ); Tue, 16 Apr 2013 10:26:35 -0400 Message-ID: <516D5F97.9050203@hp.com> Date: Tue, 16 Apr 2013 10:26:31 -0400 From: Waiman Long User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.5) Gecko/20120601 Thunderbird/10.0.5 MIME-Version: 1.0 To: Ingo Molnar CC: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , "Paul E. McKenney" , David Howells , Dave Jones , Clark Williams , Peter Zijlstra , linux-kernel@vger.kernel.org, x86@kernel.org, linux-arch@vger.kernel.org, "Chandramouleeswaran, Aswin" , Davidlohr Bueso , "Norton, Scott J" , Rik van Riel Subject: Re: [PATCH v2 2/3] mutex: Queue mutex spinners with MCS lock to reduce cacheline contention References: <1366036679-9702-1-git-send-email-Waiman.Long@hp.com> <1366036679-9702-3-git-send-email-Waiman.Long@hp.com> <20130416091026.GB9569@gmail.com> In-Reply-To: <20130416091026.GB9569@gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2035 Lines: 61 On 04/16/2013 05:10 AM, Ingo Molnar wrote: > * Waiman Long wrote: > >> --- a/kernel/sched/core.c >> +++ b/kernel/sched/core.c >> @@ -3021,9 +3021,6 @@ static inline bool owner_running(struct mutex *lock, struct task_struct *owner) >> */ >> int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner) >> { >> - if (!sched_feat(OWNER_SPIN)) >> - return 0; >> - >> rcu_read_lock(); >> while (owner_running(lock, owner)) { >> if (need_resched()) >> @@ -3040,6 +3037,27 @@ int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner) >> */ >> return lock->owner == NULL; >> } >> + >> +/* >> + * Initial check for entering the mutex spinning loop >> + */ >> +int mutex_can_spin_on_owner(struct mutex *lock) >> +{ >> + int retval = 1; >> + >> + if (!sched_feat(OWNER_SPIN)) >> + return 0; >> + >> + rcu_read_lock(); >> + if (lock->owner) >> + retval = lock->owner->on_cpu; >> + rcu_read_unlock(); >> + /* >> + * if lock->owner is not set, the mutex owner may have just acquired >> + * it and not set the owner yet or the mutex has been released. >> + */ >> + return retval; >> +} > The SCHED_FEAT_OWNER_SPIN was really just an early hack we did to make > with/without mutex-spinning testable. I see. > I'd suggest a preparatory patch that gets rid of that flag and moves these two > functions from sched/core.c to mutex.c where they belong. > > This will also allow the removal of the mutex prototypes from sched.h. Yes, I can certainly prepare a patch to remove SCHED_FEAT_OWNER_SPIN & move those functions back to mutex.c after my patch set goes in. As for the timing, do you want me to do it now or it can wait as I will start my vacation later this week and will be back by the end of the month. Regards, Longman -- 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/