linux-kernel - Re: [patch] CFS scheduler, -v19

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Message-Id: <1184671021.3188.51.camel@raven.themaw.net>
Date:	Tue, 17 Jul 2007 19:17:00 +0800
From:	Ian Kent <raven@...maw.net>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Chuck Ebbert <cebbert@...hat.com>,
	Bill Davidsen <davidsen@....com>, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [patch] CFS scheduler, -v19

On Tue, 2007-07-17 at 09:45 +0200, Ingo Molnar wrote:
> * Ian Kent <raven@...maw.net> wrote:
> 
> > Yes it does and I have two reported bugs so far.
> > 
> > In several places I have code similar to:
> > 
> > wait.tv_sec = time(NULL) + 1;
> > wait.tv_nsec = 0;
> > 
> > signaled = 0;
> > while (!signaled) {
> >         status = pthread_cond_timedwait(&cond, &mutex, &wait);
> >        if (status) {
> >              if (status == ETIMEDOUT)
> >                   break;
> >              fatal(status);
> >       }
> > }
> 
> ah! It passes in a low-res time source into a high-res time interface 
> (pthread_cond_timedwait()). Could you change the time(NULL) + 1 to 
> time(NULL) + 2, or change it to:
> 
> 	gettimeofday(&wait, NULL);
> 	wait.tv_sec++;

OK, I'm with you, hi-res timer.
But even so, how is the time in the past after adding a second.

Is it because I'm not setting tv_nsec when it's close to a second
boundary, and hence your recommendation above?

> 
> does this solve the spinning?

I don't have a system to test this on so I'll try to get one of the
people that logged the problem to test a patch.

> 
> i'm wondering how widespread this is. If automount is the only app doing 
> this then _maybe_ we could get away with it by changing automount?

I'm happy to change automount but that could cause odd version specific
problems for people updating their kernel on an older installed base.

Aaah .. and they'll all blame me!! ;)

Ian


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