Subject: Re: 2.6.27.8 scheduler bug - threads not being scheduled for long
 periods
From: Peter Zijlstra <peterz@infradead.org>
To: Dimitri Sivanich <sivanich@sgi.com>
Cc: linux-kernel@vger.kernel.org, tony.luck@intel.com,
       Ingo Molnar <mingo@elte.hu>, Mike Galbraith <efault@gmx.de>,
       Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
       Gregory Haskins <ghaskins@novell.com>, Greg KH <greg@kroah.com>,
       Nick Piggin <npiggin@suse.de>, Robin Holt <holt@sgi.com>
In-Reply-To: <20090105230218.GC20319@sgi.com>
References: <20090105175641.GA17055@sgi.com>
	 <1231188958.11687.12.camel@twins> <20090105215429.GA20319@sgi.com>
	 <20090105223621.GB20319@sgi.com>  <20090105230218.GC20319@sgi.com>
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Date: Tue, 06 Jan 2009 08:36:26 +0100
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On Mon, 2009-01-05 at 17:02 -0600, Dimitri Sivanich wrote:
> Peter,
> 
> On Mon, Jan 05, 2009 at 04:36:21PM -0600, Dimitri Sivanich wrote:
> > And sure enough, the rq->clock is sometimes going backwards.
> > 
> > The comment for sched_clock() in arch/ia64/kernel/head.S:
> >  * Return a CPU-local timestamp in nano-seconds.  This timestamp is
> >  * NOT synchronized across CPUs its return value must never be
> >  * compared against the values returned on another CPU.  The usage in
> >  * kernel/sched.c ensures that.
> > 
> > We will try this with CONFIG_HAVE_UNSTABLE_SCHED_CLOCKS.
> >
> 
> The testcase does indeed run with CONFIG_HAVE_UNSTABLE_SCHED_CLOCKS configured.

Ok, glad it worked out, thanks!
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