[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: Andi Kleen <ak@suse.de>

arch/x86_64/kernel/setup.c

@@ -732,10 +732,7 @@ 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
+	/* RDTSC can be speculated around */
 	clear_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);
 }