path: root/arch/x86_64
diff options
authorArjan van de Ven <arjan@linux.intel.com>2006-12-07 02:14:12 +0100
committerAndi Kleen <andi@basil.nowhere.org>2006-12-07 02:14:12 +0100
commitf3d73707a1e84f0687a05144b70b660441e999c7 (patch)
treed95d69b985cd8cd3f99a74350e99f7ef83b8f9b3 /arch/x86_64
parente496a0da7f8110054d0ad4039245b0f49f9540f5 (diff)
[PATCH] x86-64: Mark rdtsc as sync only for netburst, not for core2
On the Core2 cpus, the rdtsc instruction is not serializing (as defined in the architecture reference since rdtsc exists) and due to the deep speculation of these cores, it's possible that you can observe time go backwards between cores due to this speculation. Since the kernel already deals with this with the SYNC_RDTSC flag, the solution is simple, only assume that the instruction is serializing on family 15... The price one pays for this is a slightly slower gettimeofday (by a dozen or two cycles), but that increase is quite small to pay for a really-going-forward tsc counter. Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Andi Kleen <ak@suse.de>
Diffstat (limited to 'arch/x86_64')
1 files changed, 4 insertions, 1 deletions
diff --git a/arch/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c
index 05eaca41802b..6595a4ebe7f1 100644
--- a/arch/x86_64/kernel/setup.c
+++ b/arch/x86_64/kernel/setup.c
@@ -860,7 +860,10 @@ static void __cpuinit init_intel(struct cpuinfo_x86 *c)
set_bit(X86_FEATURE_CONSTANT_TSC, &c->x86_capability);
if (c->x86 == 6)
set_bit(X86_FEATURE_REP_GOOD, &c->x86_capability);
- set_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);
+ if (c->x86 == 15)
+ set_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);
+ else
+ clear_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);
c->x86_max_cores = intel_num_cpu_cores(c);