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| author | Dimitri Sivanich <sivanich@sgi.com> | 2010-03-01 11:48:15 -0600 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2010-03-02 13:36:11 +0100 |
| commit | 14be1f7454ea96ee614467a49cf018a1a383b189 (patch) | |
| tree | 803848d46600aaeb00fdd67fa0888d0c24ddfe13 /kernel/sched.c | |
| parent | 13dda80e48439b446d0bc9bab34b91484bc8f533 (diff) | |
| download | lwn-14be1f7454ea96ee614467a49cf018a1a383b189.tar.gz lwn-14be1f7454ea96ee614467a49cf018a1a383b189.zip | |
x86: Fix sched_clock_cpu for systems with unsynchronized TSC
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>
Diffstat (limited to 'kernel/sched.c')
0 files changed, 0 insertions, 0 deletions