linux-kernel - x86_64 vdso patch is broken somehow?

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Message-ID: <46D59890.3020508@redhat.com>
Date:	Wed, 29 Aug 2007 12:02:24 -0400
From:	Chuck Ebbert <cebbert@...hat.com>
To:	Andi Kleen <ak@...e.de>
CC:	linux-kernel <linux-kernel@...r.kernel.org>,
	Jakub Jelinek <jakub@...hat.com>
Subject: x86_64 vdso patch is broken somehow?

Commit:     2aae950b21e4bc789d1fc6668faf67e8748300b7

With new vdso gettimeofday support in glibc:



[https://bugzilla.redhat.com/show_bug.cgi?id=262481]

After 5 minutes of uptime, the system clock goes screwy.

When running a simple 'while /bin/true ; date ; uptime ; sleep 2 ; done' loop:


Wed Aug 29 01:01:14 EDT 2007
 01:01:14 up 4 min,  4 users,  load average: 0.13, 0.40, 0.21
Wed Aug 29 01:01:16 EDT 2007
 01:01:16 up 4 min,  4 users,  load average: 0.13, 0.40, 0.21
Wed Aug 29 02:09:36 EDT 2007
 01:01:18 up 5 min,  4 users,  load average: 0.12, 0.39, 0.21
Wed Aug 29 02:09:38 EDT 2007
 01:01:20 up 5 min,  4 users,  load average: 0.12, 0.39, 0.21
Wed Aug 29 02:09:40 EDT 2007
 01:01:22 up 5 min,  4 users,  load average: 0.19, 0.40, 0.22

At the 5 minute mark, the time jumps forward an hour as reported by date, *even
though the kernel variant appears to be unchanged*.

If you then try and reset the time (with 'date -s "01:04"):

Wed Aug 29 02:11:06 EDT 2007
 01:02:48 up 6 min,  4 users,  load average: 0.99, 0.60, 0.30
Wed Aug 29 02:12:19 EDT 2007
 01:04:01 up 6 min,  4 users,  load average: 0.99, 0.60, 0.30
Wed Aug 29 02:12:21 EDT 2007
 01:04:03 up 6 min,  4 users,  load average: 0.99, 0.61, 0.30

the kernel's date (as seen by uptime) is correctly set, but the date as returned
by /bin/date remains wrong (although it changes by the same amount.)

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