linux-kernel - Re: [RFC][PATCH 02/11] sched: Create preempt

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Message-ID: <alpine.DEB.2.11.1509291510510.4500@nanos>
Date:	Tue, 29 Sep 2015 15:11:56 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	mingo@...nel.org, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, fweisbec@...il.com, oleg@...hat.com,
	umgwanakikbuti@...il.com, rostedt@...dmis.org
Subject: Re: [RFC][PATCH 02/11] sched: Create preempt_count invariant

On Tue, 29 Sep 2015, Peter Zijlstra wrote:
> +	/*
> +	 * Still have preempt_count() == 2, from:
> +	 *
> +	 *	schedule()
> +	 *	  preempt_disable();			// 1
> +	 *	  __schedule()
> +	 *	    raw_spin_lock_irq(&rq->lock)	// 2
> +	 */
> +	rq = finish_task_switch(prev); /* drops rq->lock, preempt_count() == 1 */
>  	balance_callback(rq);
> -	preempt_enable();
> +	preempt_enable(); /* preempt_count() == 0 */

Bah. I so hate tail comments. What's wrong with

+	 /* preempt_count() ==> 0 */
	preempt_enable();

Hmm?

	tglx
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