linux-kernel - Re: [patch] change futex

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Message-ID: <20070312091628.GE28546@wotan.suse.de>
Date:	Mon, 12 Mar 2007 10:16:28 +0100
From:	Nick Piggin <npiggin@...e.de>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Roland McGrath <roland@...hat.com>, akpm@...ux-foundation.org,
	mm-commits@...r.kernel.org, drepper@...hat.com, oleg@...sign.ru,
	sebastien.dugue@...l.net, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch] change futex_wait() to hrtimers

On Mon, Mar 12, 2007 at 10:10:06AM +0100, Ingo Molnar wrote:
> 
> * Roland McGrath <roland@...hat.com> wrote:
> 
> > I agree it should restart.  But I don't think this is quite right in 
> > the timeout case.  It will increase the total maximum real time spent 
> > arbitrarily by the amount of time elapsed in signal handlers.  Other 
> > restartable, timed calls have to convert to an absolute timeout for 
> > the restart block (and convert back when doing the restart).
> 
> i dont think we should try to do this. We should not and cannot do 
> anything about all of the artifacts that comes with the use of relative 
> timeouts and schedule_timeout().
> 
> basically, using jiffies here (which schedule_timeout() does) is 
> /fundamentally/ imprecise. If you get many interrupts, rounding errors 
> sum up - and there's nothing we can do about it!

Well I did convert futex_wait to an absolute timeout based version in
the subsequent incremental patch. I think that is OK?
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