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Subject: Re: [PATCH] Instrumenting high latency
From: Arjan van de Ven <arjanv@redhat.com>
Reply-To: arjanv@redhat.com
To: Andrew Morton <akpm@osdl.org>
Cc: Con Kolivas <kernel@kolivas.org>, linux-kernel@vger.kernel.org
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	 <20040712003418.02997a12.akpm@osdl.org>
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On Mon, 2004-07-12 at 09:34, Andrew Morton wrote:
> Con Kolivas <kernel@kolivas.org> wrote:
> >
> > He hacked=20
> >  together this simple patch which times periods according to the preemp=
t=20
> >  count.
>=20
> OK, small problem.  We have code which does, effectively,
>=20
> 	if (need_resched()) {
> 		drop_the_lock();
> 		schedule();
> 		grab_the_lock();
> 	}
>=20
> so if need_resched() stays false then this will hold the lock for a long
> time and bogus reports are generated:

... or reset the time(r) in need_resched() under the assumption that all
need_resched() callers will yield when it returns true...

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