From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754764AbbDHTjl (ORCPT ); Wed, 8 Apr 2015 15:39:41 -0400 Received: from g4t3427.houston.hp.com ([15.201.208.55]:37813 "EHLO g4t3427.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752686AbbDHTjj (ORCPT ); Wed, 8 Apr 2015 15:39:39 -0400 From: Jason Low To: Peter Zijlstra , Ingo Molnar , Linus Torvalds , Davidlohr Bueso , Tim Chen , Aswin Chandramouleeswaran Cc: LKML , Jason Low Subject: [PATCH 1/2] locking/mutex: Further refactor mutex_spin_on_owner() Date: Wed, 8 Apr 2015 12:39:19 -0700 Message-Id: <1428521960-5268-2-git-send-email-jason.low2@hp.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1428521960-5268-1-git-send-email-jason.low2@hp.com> References: <1428521960-5268-1-git-send-email-jason.low2@hp.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Similar to what Linus suggested for rwsem_spin_on_owner(), in mutex_spin_on_owner() instead of having while (true) and breaking out of the spin loop on lock->owner != owner, we can have the loop directly check for while (lock->owner == owner) to improve the readability of the code. Signed-off-by: Jason Low --- kernel/locking/mutex.c | 14 ++++---------- 1 files changed, 4 insertions(+), 10 deletions(-) diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 16b2d3c..4cccea6 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -224,20 +224,14 @@ ww_mutex_set_context_slowpath(struct ww_mutex *lock, static noinline bool mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner) { - bool ret; + bool ret = true; rcu_read_lock(); - while (true) { - /* Return success when the lock owner changed */ - if (lock->owner != owner) { - ret = true; - break; - } - + while (lock->owner == owner) { /* * Ensure we emit the owner->on_cpu, dereference _after_ - * checking lock->owner still matches owner, if that fails, - * owner might point to free()d memory, if it still matches, + * checking lock->owner still matches owner. If that fails, + * owner might point to freed memory. If it still matches, * the rcu_read_lock() ensures the memory stays valid. */ barrier(); -- 1.7.2.5