From: Paul Brook <paul@codesourcery.com>
To: qemu-devel@nongnu.org
Cc: Vladimir Prus <vladimir@codesourcery.com>
Subject: Re: [Qemu-devel] Re: Fix ptimer_get_count overflow.
Date: Tue, 31 Mar 2009 14:38:26 +0000 [thread overview]
Message-ID: <200903311538.26753.paul@codesourcery.com> (raw)
In-Reply-To: <golhpd$sm5$1@ger.gmane.org>
On Wednesday 04 March 2009, Vladimir Prus wrote:
> Vladimir Prus wrote:
> > At present, ptimers have a slight inaccuracy that can lead to
> > overflow. The period is stored as 64.32 fixed point number.
> > ptimer_reload uses both integer and fractional part of the perion
> > when computing when the next event should happen. ptimer_get_count,
> > however, uses only integer part of the period. Therefore, when
> > ptimer_get_count is called very soon after ptimer_reload the value
> > returned may be greater than the value ptimer_reload has set.
> > And if the counter was 0xFFFFFFFF, this may result in overflow.
I think your patch has problems with out of range shift counts, so I applied a
slightly different version.
Paul
prev parent reply other threads:[~2009-03-31 14:38 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-12 14:33 [Qemu-devel] Fix ptimer_get_count overflow Vladimir Prus
2009-03-04 9:31 ` [Qemu-devel] " Vladimir Prus
2009-03-31 14:38 ` Paul Brook [this message]
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