From mboxrd@z Thu Jan  1 00:00:00 1970
From: oleg@redhat.com (Oleg Nesterov)
Date: Thu, 26 May 2011 19:04:22 +0200
Subject: [BUG] "sched: Remove rq->lock from the first half of ttwu()"
	locks up on ARM
In-Reply-To: <1306426148.2497.83.camel@laptop>
References: <1306343335.21578.65.camel@twins>
	<1306358128.21578.107.camel@twins>
	<BANLkTi=XbTXQsu3jUEvQyCfBy6-aRnqSpw@mail.gmail.com>
	<1306405979.1200.63.camel@twins>
	<1306407759.27474.207.camel@e102391-lin.cambridge.arm.com>
	<1306409575.1200.71.camel@twins> <1306412511.1200.90.camel@twins>
	<20110526154508.GA13788@redhat.com>
	<1306425584.2497.81.camel@laptop> <1306426148.2497.83.camel@laptop>
Message-ID: <20110526170422.GA18413@redhat.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 05/26, Peter Zijlstra wrote:
>
> @@ -2636,7 +2636,8 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
>  		 * to spin on ->on_cpu if p is current, since that would
>  		 * deadlock.
>  		 */
> -		if (p == current) {
> +		if (cpu == smp_processor_id()) {
> +			p->sched_contributes_to_load = 0;
>  			ttwu_queue(p, cpu);

Btw. I do not pretend I really understand se->vruntime, but in this
case we are doing enqueue_task() without ->task_waking(), however we
pass ENQUEUE_WAKING. Is it correct?

Oleg.