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SubjectRe: [PATCH] x86-64: Fix bad assumption that dualcore cpus have synced TSCs (resend)
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Hi John.

> This patch should resolve the issue seen in bugme bug #5105, where it
> is assumed that dualcore x86_64 systems have synced TSCs. This is not
> the case, and alternate timesources should be used instead.
>
> For more details, see:
> http://bugzilla.kernel.org/show_bug.cgi?id=5105
>
> Andi's earlier concerns that the TSCs should be synced on dualcore
> systems have been resolved by confirmation from AMD folks that they can
> be unsynced.
>
> Please consider for inclusion in your tree.

Wouldn't it be a good idea to change the comment following
the code you removed as well?

Why have a comment saying "multi socket systems" if there is no
distinction anymore?

>
> diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
> --- a/arch/x86_64/kernel/time.c
> +++ b/arch/x86_64/kernel/time.c
> @@ -959,9 +959,6 @@ static __init int unsynchronized_tsc(voi
> are handled in the OEM check above. */
> if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
> return 0;
> - /* All in a single socket - should be synchronized */
> - if (cpus_weight(cpu_core_map[0]) == num_online_cpus())
> - return 0;
> #endif
> /* Assume multi socket systems are not synchronized */
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> return num_online_cpus() > 1;

// Stefan
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