From 616779656989cb8c59177e35cb13e87028b1edc8 Mon Sep 17 00:00:00 2001 From: Andi Kleen <ak@suse.de> Date: Thu, 7 Dec 2006 02:14:12 +0100 Subject: [PATCH] [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 | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/arch/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c index a570c81c8316..05eaca41802b 100644 --- a/arch/x86_64/kernel/setup.c +++ b/arch/x86_64/kernel/setup.c @@ -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)