Re: [PATCH] x86-64: Fix bad assumption that dualcore cpus have syncedTSCs (resend)

[Stefan Smietanowski]

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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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