From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752488AbZKPFdy (ORCPT ); Mon, 16 Nov 2009 00:33:54 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751972AbZKPFdy (ORCPT ); Mon, 16 Nov 2009 00:33:54 -0500 Received: from mail-yw0-f202.google.com ([209.85.211.202]:47835 "EHLO mail-yw0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751757AbZKPFdx (ORCPT ); Mon, 16 Nov 2009 00:33:53 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer; b=mJAMhUJ6nRc3q3Q0LGBuMrK0+vSx3HumkhGXIPDf+0yyZq4t2Al/ZeYHrxJv4X/5PM rHAq41mEzvCQygrwKYmmpg4rMoIZFcSUzjBIK6nyD7QnSE1m+Mh6fnpzXdiu/xY92OmZ s7HkUndT5WKqfAw1m/+XS3+QBAzxgfzuXM2Ys= From: Jupyung Lee To: LKML Cc: Thomas Gleixner , Jupyung Lee Subject: [PATCH -rt 1/1] sched_rt: change spinlock primitive in post_schedule_rt() Date: Mon, 16 Nov 2009 14:33:39 +0900 Message-Id: <1258349619-7267-1-git-send-email-jupyung@gmail.com> X-Mailer: git-send-email 1.6.5.GIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In the function post_schedule_rt() of the current preempt-rt kernel, push_rt_task() is surrounded by atomic_spin_lock_irq(&rq->lock) and atomic_spin_unlock_irq(&rq->lock), which means that the function is called with the runqueue lock held and the interrupt disabled. A problem is that after finishing post_schedule_rt(), interrupt is always re-enabled regardless of the previous condition. In practice, the function post_schedule_rt() is called by finish_task_switch() with the interrupt disabled. Thus, the interrupt should not be re-enabled at the moment. The problem can simply be resolved by replacing atomic_spin_lock_irq() and atomic_spin_unlock_irq() with atomic_spin_lock_irqsave() and atomic_spin_unlock_irqrestore(). As a sidenote, the other way to resolve the problem might be to modify codes in accordance with commit 3f029d3c6d62068d59301d90c18dbde8ee402107, titled "sched: Enhance the pre/post scheduling logic", in the vanilla tree. Signed-off-by: Jupyung Lee --- kernel/sched_rt.c | 5 +++-- 1 files changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c index 274c976..bd16998 100644 --- a/kernel/sched_rt.c +++ b/kernel/sched_rt.c @@ -1536,9 +1536,10 @@ static void post_schedule_rt(struct rq *rq) * This is only called if needs_post_schedule_rt() indicates that * we need to push tasks away */ - atomic_spin_lock_irq(&rq->lock); + unsigned long flags; + atomic_spin_lock_irqsave(&rq->lock, flags); push_rt_tasks(rq); - atomic_spin_unlock_irq(&rq->lock); + atomic_spin_unlock_irqrestore(&rq->lock, flags); } /* -- 1.6.5.GIT