linux-kernel - Re: [patch] change futex

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Message-Id: <1173698386.13341.87.camel@localhost.localdomain>
Date:	Mon, 12 Mar 2007 12:19:45 +0100
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Nick Piggin <npiggin@...e.de>, 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
Subject: Re: [patch] change futex_wait() to hrtimers

On Mon, 2007-03-12 at 12:02 +0100, Ingo Molnar wrote:
> > Well I did convert futex_wait to an absolute timeout based version in 
> > the subsequent incremental patch. I think that is OK?
> 
> it still has the rounding artifacts: using timer_list there is no way to 
> do a precise long sleep based on many small sleeps.
> 
> even if this means more work for you (i'm sorry about that!) i'm quite 
> sure we should take Sebastien's hrtimers based implementation of 
> futex_wait(), and use the nanosleep method to restart it. There's no 
> point in further tweaking the imprecise approach: whenever some timeout 
> needs to be restarted, it's a candidate for hrtimers.
> 
> until then, glibc already handles timeouts and restarts it manually.

This also allows us to add a seperate absolute time bases futex op,
which allows to remove the conversion of abstime to reltime in glibc.

	tglx


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