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Bug#594742: libc6: clock_gettime(CLOCK_MONOTONIC) not monotonic



On Tue, 2010-08-31 at 22:34 +0200, Aurelien Jarno wrote:
[...]
> The GNU libc simply uses a kernel syscall to get this time. My guess is
> that it happens when the thread is moving from one CPU to another, the
> RDTSC are jumping are they are not synchronized.

The implementation isn't so stupid as to trust TSCs entirely.

> Anyway, as I think it is a kernel bug, I am reassigning it to this
> package.

I think this bug may have been fixed in Linux 2.6.33 by:

commit 0696b711e4be45fa104c12329f617beb29c03f78
Author: Lin Ming <ming.m.lin@intel.com>
Date:   Tue Nov 17 13:49:50 2009 +0800

    timekeeping: Fix clock_gettime vsyscall time warp

which was then backported into stable kernel 2.6.32.19 and Debian
version 2.6.32-21.  Manuel, please update your kernel to 2.6.32-21 and
re-test.

Ben.

-- 
Ben Hutchings
Once a job is fouled up, anything done to improve it makes it worse.

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