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From: Andi Kleen <andi@firstfloor.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: mingo@elte.hu, tglx@linutronix.de, linux-kernel@vger.kernel.org
Subject: Re: More breakage in native_rdtsc out of line in git-x86 II
Date: Wed, 9 Jan 2008 06:21:44 +0100	[thread overview]
Message-ID: <20080109052144.GA21032@basil.nowhere.org> (raw)
In-Reply-To: <20080109035534.GA30321@basil.nowhere.org>

> I think the problem is that the vsyscall/vdso code calls it through
> vread and for that it has to be exported. There seems to be also
> another bug with the old style vsyscalls not using the TSC vread
> that masks it on older glibc
> 
> Stepping with gdb through old style vgettimeofday() confirms that RDTSC is 
> not used.
> 
> A long time ago we had a similar problem once and it was because of a 
> problem exporting the vsyscall variables in vmlinux.lds.S -- looks like that 
> has reappeared.
> 
> I think the new glibc shows it because it uses the vDSO not 
> the older vsyscall and the new vDSO probably still works. Anyways haven't 
> investigated why that is in detail yet, but that's a separate 
> regression.

Actually that seems to be because the test system using the older 
glibc didn't use the TSC because it was marked unstable due a 
unsynchronized TSC. It should not have been -- this is a Core2 
dual core single socket. Will investigate later what happened
there.

-Andi

  reply	other threads:[~2008-01-09  5:21 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-09  3:55 More breakage in native_rdtsc out of line in git-x86 Andi Kleen
2008-01-09  5:21 ` Andi Kleen [this message]
2008-01-09  9:09 ` Ingo Molnar
2008-01-09 14:19   ` Andi Kleen
2008-01-09 15:22     ` Ingo Molnar
2008-01-09 15:51       ` Andi Kleen
2008-01-09 16:30         ` Ingo Molnar
2008-01-09 17:48           ` Andi Kleen
2008-01-09 20:25             ` Arjan van de Ven
2008-01-09 20:40               ` Andi Kleen
2008-01-09 20:57                 ` H. Peter Anvin
2008-01-09 22:09             ` Björn Steinbrink
2008-01-09 22:28               ` Andi Kleen
2008-01-09 22:35                 ` Harvey Harrison
2008-01-09 22:41                   ` Andi Kleen
2008-01-09 23:21                     ` Björn Steinbrink
2008-01-09 23:37                     ` Paolo Ciarrocchi
2008-01-11  5:21                       ` Cyrill Gorcunov

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