linux-kernel - Re: 2.6.23-rc3-mm1

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Date:	Wed, 29 Aug 2007 10:04:33 -0400
From:	Valdis.Kletnieks@...edu
To:	Andrew Morton <akpm@...ux-foundation.org>, jakub@...hat.com,
	Ulrich Drepper <drepper@...hat.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: 2.6.23-rc3-mm1

On Wed, 22 Aug 2007 02:06:48 PDT, Andrew Morton said:
> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.23-rc3/2.6.23-rc3-mm1/

Sorry for not catching this one sooner, but AFAICT, Fedora didn't ship a glibc
that trips over this (2.6.90-12) until Saturday and I installed it yesterday.
-22-rc6-mm1 demonstrated the same issue as well.

The issue:  vdso and gettimeofday seem to be having a quarrel.

At boot, the system clock is just fine.   Right when it hits the 5-minute
uptime mark (and suspiciously close to the jiffie rollover), the date suddenly
shoots forward 4096 seconds.

Dumb test script:

#!/bin/bash
log="uptime.`uname -r`"
touch /root/$log
tail -f /root/$log &
while /bin/true;
do
        uptime >> /root/$log
        date >> /root/$log
        sleep 1
done

Exerpt from runtime:

 19:57:55 up 1 min,  0 users,  load average: 0.09, 0.05, 0.01
Tue Aug 28 19:57:55 EDT 2007
 19:57:56 up 1 min,  0 users,  load average: 0.09, 0.05, 0.01
Tue Aug 28 19:57:56 EDT 2007
 19:57:57 up 2 min,  0 users,  load average: 0.08, 0.05, 0.01
Tue Aug 28 19:57:57 EDT 2007
 19:57:58 up 2 min,  0 users,  load average: 0.08, 0.05, 0.01
...
 20:00:55 up 4 min,  0 users,  load average: 0.01, 0.03, 0.00
Tue Aug 28 20:00:55 EDT 2007
 20:00:56 up 4 min,  0 users,  load average: 0.01, 0.03, 0.00
Tue Aug 28 20:00:56 EDT 2007
 20:00:57 up 5 min,  0 users,  load average: 0.01, 0.03, 0.00
Tue Aug 28 21:09:15 EDT 2007
 20:00:58 up 5 min,  0 users,  load average: 0.01, 0.03, 0.00
Tue Aug 28 21:09:16 EDT 2007
 20:00:59 up 5 min,  0 users,  load average: 0.01, 0.03, 0.00
Tue Aug 28 21:09:17 EDT 2007

uptime keeps reporting the right time, date goes flying ahead.  Once we
get into this state, I can issue a 'date' command to set the *right* time,
and then it will immediately reset back.  Doing a 'touch foo; ls -l foo'
shows the correct time.

Booting with vdso=0 makes the time/date run normally.

Ideas?

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