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| author | Dimitri Sivanich <sivanich@sgi.com> | 2010-03-01 11:48:15 -0600 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-04-01 15:58:57 -0700 |
| commit | 847d52cc4a3e149949df66d7484aba999dc61e19 (patch) | |
| tree | 9c5d99c9e7cc8462c028833f1f81e56bd99c3aac | |
| parent | 37c3a08ca3714118fe8f931f28b2cc76bb4ac0e5 (diff) | |
| download | lwn-847d52cc4a3e149949df66d7484aba999dc61e19.tar.gz lwn-847d52cc4a3e149949df66d7484aba999dc61e19.zip | |
x86: Fix sched_clock_cpu for systems with unsynchronized TSC
commit 14be1f7454ea96ee614467a49cf018a1a383b189 upstream.
On UV systems, the TSC is not synchronized across blades. The
sched_clock_cpu() function is returning values that can go
backwards (I've seen as much as 8 seconds) when switching
between cpus.
As each cpu comes up, early_init_intel() will currently set the
sched_clock_stable flag true. When mark_tsc_unstable() runs, it
clears the flag, but this only occurs once (the first time a cpu
comes up whose TSC is not synchronized with cpu 0). After this,
early_init_intel() will set the flag again as the next cpu comes
up.
Only set sched_clock_stable if tsc has not been marked unstable.
Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
Acked-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20100301174815.GC8224@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | arch/x86/kernel/cpu/intel.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index a2a03cf4a489..2a94890149db 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -70,7 +70,8 @@ static void __cpuinit early_init_intel(struct cpuinfo_x86 *c) if (c->x86_power & (1 << 8)) { set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC); set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC); - sched_clock_stable = 1; + if (!check_tsc_unstable()) + sched_clock_stable = 1; } /* |