From: Philipp Rumpf <prumpf@parcelfarce.linux.theplanet.co.uk>
To: Jeff Garzik <jgarzik@mandrakesoft.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: jiffies wrap question...
Date: Fri, 10 Nov 2000 07:35:29 +0000 [thread overview]
Message-ID: <20001110073529.K2272@parcelfarce.linux.theplanet.co.uk> (raw)
In-Reply-To: <3A0BA1F8.E3ABCD18@mandrakesoft.com>
In-Reply-To: <3A0BA1F8.E3ABCD18@mandrakesoft.com>; from jgarzik@mandrakesoft.com on Fri, Nov 10, 2000 at 02:21:28AM -0500
On Fri, Nov 10, 2000 at 02:21:28AM -0500, Jeff Garzik wrote:
> The following is a piece of code from the latter half of
> schedule_timeout, in kernel/sched.c. Is it possible that
> schedule_timeout could return an incorrect value, if the jiffy value
> wraps between the first and last lines shown below.
let's say the first line happens n ticks before the wrap and the second,
m ticks afterwards.
> expire = timeout + jiffies;
expire = timeout + 2^32/2^64 - n = timeout - n
> timeout = expire - jiffies;
timeout = expire - m = timeout - n - m = timeout - (n+m)
(n+m) is the time that actually passed while we were asleep, and timeout
has the correct value (timeout - ticks that happened)>
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prev parent reply other threads:[~2000-11-10 7:35 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-11-10 7:21 Jeff Garzik
2000-11-10 7:35 ` Philipp Rumpf [this message]
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