linux-kernel - Re: [PATCH v4 1/2] sched/rt: Check to push the task away after its affinity was changed

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Date:	Mon, 6 Jul 2015 14:48:27 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Xunlei Pang <xlpang@....com>
Cc:	linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
	Juri Lelli <juri.lelli@...il.com>,
	Ingo Molnar <mingo@...hat.com>,
	Xunlei Pang <pang.xunlei@...aro.org>
Subject: Re: [PATCH v4 1/2] sched/rt: Check to push the task away after its
 affinity was changed

On Sat, Jul 04, 2015 at 03:21:22PM +0800, Xunlei Pang wrote:
> @@ -1187,6 +1227,14 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
>  	}
>  
>  	do_set_cpus_allowed(p, new_mask);
> +	/*
> +	 * rq->lock might get released during __balance_callback(),
> +	 * but if there's any successful migrating of @p, task_cpu(p)
> +	 * will obviously be in the new_mask, as p->pi_lock is never
> +	 * released; Thus, subsequent cpumask_test_cpu() is true and
> +	 * will make it return safely in such case.
> +	 */
> +	__balance_callback(rq);
>  
>  	/* Can the task run on the task's current CPU? If so, we're done */
>  	if (cpumask_test_cpu(task_cpu(p), new_mask))

This will trigger the lockdep_pin stuff.
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