From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965825AbcCJLHA (ORCPT ); Thu, 10 Mar 2016 06:07:00 -0500 Received: from torg.zytor.com ([198.137.202.12]:38330 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S965629AbcCJLGy (ORCPT ); Thu, 10 Mar 2016 06:06:54 -0500 Date: Thu, 10 Mar 2016 03:06:14 -0800 From: tip-bot for Davidlohr Bueso Message-ID: Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, dbueso@suse.de, hpa@zytor.com, torvalds@linux-foundation.org, mingo@kernel.org, peterz@infradead.org Reply-To: linux-kernel@vger.kernel.org, tglx@linutronix.de, dbueso@suse.de, hpa@zytor.com, torvalds@linux-foundation.org, peterz@infradead.org, mingo@kernel.org In-Reply-To: <1457574936-19065-3-git-send-email-dbueso@suse.de> References: <1457574936-19065-3-git-send-email-dbueso@suse.de> To: linux-tip-commits@vger.kernel.org Subject: [tip:locking/core] locking/csd_lock: Use smp_cond_acquire() in csd_lock_wait() Git-Commit-ID: 38460a2178d225b39ade5ac66586c3733391cf86 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 38460a2178d225b39ade5ac66586c3733391cf86 Gitweb: http://git.kernel.org/tip/38460a2178d225b39ade5ac66586c3733391cf86 Author: Davidlohr Bueso AuthorDate: Wed, 9 Mar 2016 17:55:36 -0800 Committer: Ingo Molnar CommitDate: Thu, 10 Mar 2016 10:28:35 +0100 locking/csd_lock: Use smp_cond_acquire() in csd_lock_wait() We can micro-optimize this call and mildly relax the barrier requirements by relying on ctrl + rmb, keeping the acquire semantics. In addition, this is pretty much the now standard for busy-waiting under such restraints. Signed-off-by: Davidlohr Bueso Acked-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dave@stgolabs.net Link: http://lkml.kernel.org/r/1457574936-19065-3-git-send-email-dbueso@suse.de Signed-off-by: Ingo Molnar --- kernel/smp.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/smp.c b/kernel/smp.c index 5099db1..300d293 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -107,8 +107,7 @@ void __init call_function_init(void) */ static __always_inline void csd_lock_wait(struct call_single_data *csd) { - while (smp_load_acquire(&csd->flags) & CSD_FLAG_LOCK) - cpu_relax(); + smp_cond_acquire(!(csd->flags & CSD_FLAG_LOCK)); } static __always_inline void csd_lock(struct call_single_data *csd)