Re: Bug: timer going backward on a dual core

From: Vladimir Lazarenko
Date: Fri Oct 28 2005 - 16:50:40 EST


We have a dual-core AMD64 with the new kernel 2.6.14 and the
timer goes backward...


CONFIGURATION:

Kernel: 2.6.14
Distribution: Gentoo Linux 2005.0
Processor: Athlon 64 x2 4200+ (dual core)
Motherboard: Abit KN8
Memory: 1GB PC3200


PROBLEM:

gettimeofday goes backward and returns values that are not monotonic,
giving values that are smaller than values returned before.

The system has been tested with timer as PIT, PIT/TSC and PM and the
problem occurs with all the configurations.

Here is the config file that we used for the PM configuration.

Any suggestion ?

Booting w/ idle=poll tends to work around this issue. You might check
with your motherboard vendor for an updated BIOS that supports HPET or
the ACPI PM timer.

We already updated the BIOS with the latest version.

Also the booting command idle=poll doesn't work.

Hmm. Not sure then. Is this a new regression on the same hardware?
Yes, we tried with idle=poll and the problem occurred again.

Very strange, idle=poll fixed it for us just fine.

Configuration we use is as follows:
Athlon 64 X2 3800+
Debian 32-bit
Tyan K8E
4G PC3200

Vladimir

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