From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755061Ab0DBTMr (ORCPT ); Fri, 2 Apr 2010 15:12:47 -0400 Received: from hera.kernel.org ([140.211.167.34]:38822 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754866Ab0DBTMl (ORCPT ); Fri, 2 Apr 2010 15:12:41 -0400 Date: Fri, 2 Apr 2010 19:12:17 GMT From: tip-bot for Oleg Nesterov Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, a.p.zijlstra@chello.nl, oleg@redhat.com, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, tglx@linutronix.de, oleg@redhat.com, mingo@elte.hu In-Reply-To: <20100315091014.GA9138@redhat.com> References: <20100315091014.GA9138@redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched: move_task_off_dead_cpu(): Remove retry logic Message-ID: Git-Commit-ID: c1804d547dc098363443667609c272d1e4d15ee8 X-Mailer: tip-git-log-daemon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Fri, 02 Apr 2010 19:12:17 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: c1804d547dc098363443667609c272d1e4d15ee8 Gitweb: http://git.kernel.org/tip/c1804d547dc098363443667609c272d1e4d15ee8 Author: Oleg Nesterov AuthorDate: Mon, 15 Mar 2010 10:10:14 +0100 Committer: Ingo Molnar CommitDate: Fri, 2 Apr 2010 20:12:02 +0200 sched: move_task_off_dead_cpu(): Remove retry logic The previous patch preserved the retry logic, but it looks unneeded. __migrate_task() can only fail if we raced with migration after we dropped the lock, but in this case the caller of set_cpus_allowed/etc must initiate migration itself if ->on_rq == T. We already fixed p->cpus_allowed, the changes in active/online masks must be visible to racer, it should migrate the task to online cpu correctly. Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra LKML-Reference: <20100315091014.GA9138@redhat.com> Signed-off-by: Ingo Molnar --- kernel/sched.c | 13 ++++++------- 1 files changed, 6 insertions(+), 7 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index 27774b5..f475c60 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -5456,7 +5456,7 @@ static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p) struct rq *rq = cpu_rq(dead_cpu); int needs_cpu, uninitialized_var(dest_cpu); unsigned long flags; -again: + local_irq_save(flags); raw_spin_lock(&rq->lock); @@ -5464,14 +5464,13 @@ again: if (needs_cpu) dest_cpu = select_fallback_rq(dead_cpu, p); raw_spin_unlock(&rq->lock); - - /* It can have affinity changed while we were choosing. */ + /* + * It can only fail if we race with set_cpus_allowed(), + * in the racer should migrate the task anyway. + */ if (needs_cpu) - needs_cpu = !__migrate_task(p, dead_cpu, dest_cpu); + __migrate_task(p, dead_cpu, dest_cpu); local_irq_restore(flags); - - if (unlikely(needs_cpu)) - goto again; } /*