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Commit 61677965 authored by Andi Kleen's avatar Andi Kleen Committed by Andi Kleen
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[PATCH] x86-64: Synchronize RDTSC on single core AMD 



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: default avatarAndi Kleen <ak@suse.de>
parent a1a70c25

arch/x86_64/kernel/setup.c

+2 −5
Original line number Original line Diff line number Diff line
@@ -732,10 +732,7 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c) 
	/* Fix cpuid4 emulation for more */

	/* Fix cpuid4 emulation for more */

	num_cache_leaves = 3;

	num_cache_leaves = 3;





	/* When there is only one core no need to synchronize RDTSC */

	/* RDTSC can be speculated around */

	if (num_possible_cpus() == 1)

	        set_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);

	else

	clear_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);

	clear_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);

}

}