linux-kernel - Re: [PATCH] locking/ww_mutex: Replace cpu_relax with cond

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Message-ID: <20170228095821.GK10304@nuc-i3427.alporthouse.com>
Date:   Tue, 28 Feb 2017 09:58:21 +0000
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: [PATCH] locking/ww_mutex: Replace cpu_relax with cond_resched
 for tests

On Tue, Feb 28, 2017 at 10:48:53AM +0100, Peter Zijlstra wrote:
> On Tue, Feb 28, 2017 at 09:40:11AM +0000, Chris Wilson wrote:
> > When busy-spinning on a ww_mutex_trylock(), we depend upon the other
> > thread advancing and releasing the lock. This can not happen on a single
> > CPU unless we relinquish it.
> 
> Thanks, do you have any clue about those other ww-mutex test fails? So
> far I've not had much luck poking at them.

Not yet, they didn't seem quite so self-explanatory as this trace :(
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre