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

From: Peter Zijlstra
Date: Thu Dec 03 2015 - 08:29:48 EST


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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