Messages in this thread |  | | | Date | Wed, 9 Jan 2008 06:21:44 +0100 | | From | Andi Kleen <> | | Subject | Re: More breakage in native_rdtsc out of line in git-x86 II | |
> 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
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