linux-kernel - Re: [PATCH/RFC] wait_for_completion

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Date:	Tue, 19 Nov 2013 08:05:57 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Jonathan Corbet <corbet@....net>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	NeilBrown <neilb@...e.de>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	lkml <linux-kernel@...r.kernel.org>,
	"Dr. H. Nikolaus Schaller" <hns@...delico.com>,
	Marek Belisko <marek@...delico.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH/RFC] wait_for_completion_timeout() considered harmful.


* Jonathan Corbet <corbet@....net> wrote:

> On Tue, 19 Nov 2013 00:42:09 +0100
> Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > I briefly talked to Thomas about this earlier today and we need to 
> > fix this at a lower level -- the quick 'n dirty solution is to add 
> > 1 jiffy down in the timer-wheel when we enqueue these things.
> 
> That can lead to situations like the one I encountered years ago 
> where msleep(1) would snooze for 20ms.  I didn't get much love for 
> my idea of switching msleep() to hrtimers back then, but I still 
> think it might be be better to provide the resolution that the 
> interface appears to promise.

That looks like a sensible approach - mind resending that patch? We 
can put it into the timer tree and see what happens.

Thanks,

	Ingo
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