From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756558AbZGPG2U (ORCPT ); Thu, 16 Jul 2009 02:28:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754012AbZGPG2U (ORCPT ); Thu, 16 Jul 2009 02:28:20 -0400 Received: from qw-out-2122.google.com ([74.125.92.25]:59564 "EHLO qw-out-2122.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752766AbZGPG2T (ORCPT ); Thu, 16 Jul 2009 02:28:19 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer; b=IOGnDOcOAtjDplhVqEp01yOnVfFFB+cxO+NX1wB7jhot3vEhuKdAR90/r+ZdmanL+e vW03LAq6JU8e4jvj6MWz4j8Qn4VUSi+Uzs9Mq+6Npap0JxGMcctwF0RGD99ZS+Bp3GCf m0AnzgMzGDRIworUMv4fPVGQoghupodoDq8XE= From: Frederic Weisbecker To: Ingo Molnar Cc: LKML , Frederic Weisbecker , Peter Zijlstra , Thomas Gleixner Subject: [PATCH 1/7] sched: Drop the need_resched() loop from cond_resched() Date: Thu, 16 Jul 2009 02:28:08 -0400 Message-Id: <1247725694-6082-1-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.6.2.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The schedule() function is a loop that reschedules the current task while the TIF_NEED_RESCHED flag is set: void schedule(void) { need_resched: /* schedule code */ if (need_resched()) goto need_resched; } And cond_resched() repeat this loop: do { add_preempt_count(PREEMPT_ACTIVE); schedule(); sub_preempt_count(PREEMPT_ACTIVE); } while(need_resched()); This loop is needless because schedule() already did the check and nothing can set TIF_NEED_RESCHED between schedule() exit and the loop check in need_resched(). Then remove this needless loop. Signed-off-by: Frederic Weisbecker Acked-by: Peter Zijlstra --- kernel/sched.c | 8 +++----- 1 files changed, 3 insertions(+), 5 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index 75d2c1d..264b163 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -6618,11 +6618,9 @@ static void __cond_resched(void) * PREEMPT_ACTIVE, which could trigger a second * cond_resched() call. */ - do { - add_preempt_count(PREEMPT_ACTIVE); - schedule(); - sub_preempt_count(PREEMPT_ACTIVE); - } while (need_resched()); + add_preempt_count(PREEMPT_ACTIVE); + schedule(); + sub_preempt_count(PREEMPT_ACTIVE); } int __sched _cond_resched(void) -- 1.6.2.3