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

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Message-Id: <1184738344.4178.18.camel@raven.themaw.net>
Date:	Wed, 18 Jul 2007 13:59:04 +0800
From:	Ian Kent <raven@...maw.net>
To:	davids@...master.com
Cc:	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
	Chuck Ebbert <cebbert@...hat.com>,
	Bill Davidsen <davidsen@....com>
Subject: RE: [patch] CFS scheduler, -v19

On Tue, 2007-07-17 at 14:16 -0700, David Schwartz 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++;
> >
> > does this solve the spinning?

Yes, adding in the offset within the current second appears to resolve
the issue. Thanks Ingo.

> >
> > 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 don't think the change is unreasonable since I wasn't using an
accurate time in the condition wait, so that's a coding mistake on my
part which I will fix.

Ian


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