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author | Ingo Molnar <mingo@elte.hu> | 2007-02-16 01:27:34 -0800 |
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committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-02-16 08:13:57 -0800 |
commit | 95492e4646e5de8b43d9a7908d6177fb737b61f0 (patch) | |
tree | ae25cd206ca76f78d50ac2a206ef012e0ab1d9df /arch/x86_64/kernel/time.c | |
parent | 92c7e00254b2d0efc1e36ac3e45474ce1871b6b2 (diff) | |
download | op-kernel-dev-95492e4646e5de8b43d9a7908d6177fb737b61f0.zip op-kernel-dev-95492e4646e5de8b43d9a7908d6177fb737b61f0.tar.gz |
[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 <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/x86_64/kernel/time.c')
-rw-r--r-- | arch/x86_64/kernel/time.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c index 3cc6886..8cb2b2d 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; |