linux-kernel - Re: [PATCH] i386 Time: Avoid PIT SMP lockups

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Date:	Mon, 16 Oct 2006 11:39:37 -0700
From:	Andrew Morton <akpm@...l.org>
To:	Andi Kleen <ak@...e.de>
Cc:	lkml <linux-kernel@...r.kernel.org>, johnstul@...ibm.com
Subject: Re: [PATCH] i386 Time: Avoid PIT SMP lockups

On 16 Oct 2006 15:48:02 +0200
Andi Kleen <ak@...e.de> wrote:

> Andrew Morton <akpm@...l.org> writes:
> > 
> > Is there any actual need to hold xtime_lock while doing the port IO?  I'd
> > have thought it would suffice to do
> > 
> > 	temp = port_io
> > 	write_seqlock(xtime_lock);
> > 	xtime = muck_with(temp);
> > 	write_sequnlock(xtime_lock);
> > 
> > ?
> 
> That would be a good idea in general. The trouble is just that whatever race
> is there will be still there then, just harder to trigger (so instead of 
> every third boot it will muck up every 6 weeks). Not sure that is
> a real improvement.
> 

Confused.  What race are you referring to?

This is addressing a starvation problem which is due to the slowness of the
port-io (iirc).

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