From 95492e4646e5de8b43d9a7908d6177fb737b61f0 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Fri, 16 Feb 2007 01:27:34 -0800 Subject: [PATCH] x86: rewrite SMP TSC sync code make the TSC synchronization code more robust, and unify it between x86_64 and i386. The biggest change is the removal of the 'fix up TSCs' code on x86_64 and i386, in some rare cases it was /causing/ time-warps on SMP systems. The new code only checks for TSC asynchronity - and if it can prove a time-warp (if it can observe the TSC going backwards when going from one CPU to another within a critical section), then the TSC clock-source is turned off. The TSC synchronization-checking code also got moved into a separate file. Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner Cc: john stultz Cc: Roman Zippel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/x86_64/kernel/time.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'arch/x86_64/kernel/time.c') diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c index 3cc6886f1fb..8cb2b2d35f5 100644 --- a/arch/x86_64/kernel/time.c +++ b/arch/x86_64/kernel/time.c @@ -944,12 +944,23 @@ void __init time_init(void) #endif } +static int tsc_unstable = 0; + +void mark_tsc_unstable(void) +{ + tsc_unstable = 1; +} +EXPORT_SYMBOL_GPL(mark_tsc_unstable); + /* * Make an educated guess if the TSC is trustworthy and synchronized * over all CPUs. */ __cpuinit int unsynchronized_tsc(void) { + if (tsc_unstable) + return 1; + #ifdef CONFIG_SMP if (apic_is_clustered_box()) return 1; -- cgit v1.2.3