linux-kernel - Re: [PATCH 4/4] sched: Document Program-Order guarantees

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Message-ID: <20151203132938.GB3816@twins.programming.kicks-ass.net>
Date:	Thu, 3 Dec 2015 14:29:38 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Boqun Feng <boqun.feng@...il.com>
Cc:	mingo@...nel.org, oleg@...hat.com, linux-kernel@...r.kernel.org,
	paulmck@...ux.vnet.ibm.com, corbet@....net, mhocko@...nel.org,
	dhowells@...hat.com, torvalds@...ux-foundation.org,
	will.deacon@....com, waiman.long@....com, pjt@...gle.com
Subject: Re: [PATCH 4/4] sched: Document Program-Order guarantees

On Thu, Dec 03, 2015 at 09:16:48PM +0800, Boqun Feng wrote:
> On Thu, Dec 03, 2015 at 01:40:14PM +0100, Peter Zijlstra wrote:
> [snip]
> > + *
> > + *   CPU0 (schedule)  CPU1 (try_to_wake_up) CPU2 (schedule)
> > + *
> > + *   LOCK rq(0)->lock LOCK X->pi_lock
> > + *   dequeue X
> > + *   sched-out X
> > + *   smp_store_release(X->on_cpu, 0);
> > + *
> > + *                    smp_cond_acquire(!X->on_cpu);
> > + *                    X->state = WAKING
> > + *                    set_task_cpu(X,2)
> > + *
> > + *                    LOCK rq(2)->lock
> > + *                    enqueue X
> > + *                    X->state = RUNNING
> > + *                    UNLOCK rq(2)->lock
> > + *
> > + *                                          LOCK rq(2)->lock // orders against CPU1
> > + *                                          sched-out Z
> > + *                                          sched-in X
> > + *                                          UNLOCK rq(1)->lock
> 						^^^^^^^^^^^^^^^
> 
> This is a typo, right? Should be "UNLOCK rq(2)->lock".

Duh, yes. Fixed.

Thanks.
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