From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756086Ab0IRTMo (ORCPT ); Sat, 18 Sep 2010 15:12:44 -0400 Received: from kroah.org ([198.145.64.141]:51733 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754649Ab0IRTCN (ORCPT ); Sat, 18 Sep 2010 15:02:13 -0400 X-Mailbox-Line: From gregkh@clark.site Sat Sep 18 12:00:01 2010 Message-Id: <20100918190000.964013055@clark.site> User-Agent: quilt/0.48-11.2 Date: Sat, 18 Sep 2010 11:58:59 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Ingo Molnar , Peter Zijlstra , Greg KH , Oleg Nesterov , Mike Galbraith Subject: [095/123] sched: move_task_off_dead_cpu(): Remove retry logic References: <20100918185724.290702750@clark.site> Content-Disposition: inline; filename=sched-move_task_off_dead_cpu-remove-retry-logic.patch In-Reply-To: <20100918190024.GA14388@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Oleg Nesterov commit c1804d547dc098363443667609c272d1e4d15ee8 upstream 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 Signed-off-by: Mike Galbraith Signed-off-by: Greg Kroah-Hartman --- kernel/sched.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) --- a/kernel/sched.c +++ b/kernel/sched.c @@ -7407,7 +7407,7 @@ static void move_task_off_dead_cpu(int d struct rq *rq = cpu_rq(dead_cpu); int needs_cpu, uninitialized_var(dest_cpu); unsigned long flags; -again: + local_irq_save(flags); spin_lock(&rq->lock); @@ -7415,14 +7415,13 @@ again: if (needs_cpu) dest_cpu = select_fallback_rq(dead_cpu, p); 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; } /*