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[PATCH] x86-64: Synchronize RDTSC on single core AMD

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There is no guarantee that two RDTSCs in a row are monotonic,
so don't assume it on single core AMD systems.
This will make gettimeofday slower again
Signed-off-by: Andi Kleen <ak@suse.de>
This commit is contained in:
Andi Kleen 2006-12-07 02:14:12 +01:00 committed by Andi Kleen
parent a1a70c25be
commit 6167796569
1 changed files with 2 additions and 5 deletions
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7
arch/x86_64/kernel/setup.c
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@ -732,11 +732,8 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
/* Fix cpuid4 emulation for more */
num_cache_leaves = 3;
/* When there is only one core no need to synchronize RDTSC */
if (num_possible_cpus() == 1)
set_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);
else
clear_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);
/* RDTSC can be speculated around */
clear_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);
}
static void __cpuinit detect_ht(struct cpuinfo_x86 *c)