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| author | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2009-08-14 15:47:20 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2009-08-15 10:55:45 +0200 |
| commit | 1be396794897f80bfc8774719ba60309a9e3d374 (patch) | |
| tree | f0e11ffe7b7cc2cf58129cf3ea1c543de0da9898 /kernel/time | |
| parent | timekeeping: Remove clocksource inline functions (diff) | |
| download | linux-1be396794897f80bfc8774719ba60309a9e3d374.tar.xz linux-1be396794897f80bfc8774719ba60309a9e3d374.zip | |
timekeeping: Move reset of cycle_last for tsc clocksource to tsc
change_clocksource resets the cycle_last value to zero then sets it to
a value read from the clocksource. The reset to zero is required only
for the TSC clocksource to make the read_tsc function work after a
resume. The reason is that the TSC read function uses cycle_last to
detect backwards going TSCs. In the resume case cycle_last contains
the TSC value from the last update before the suspend. On resume the
TSC starts counting from 0 again and would trip over the cycle_last
comparison.
This is subtle and surprising. Move the reset to a resume function in
the tsc code.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Daniel Walker <dwalker@fifo99.com>
LKML-Reference: <20090814134808.142191175@de.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/time')
| -rw-r--r-- | kernel/time/timekeeping.c | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 016a2591d719..b5673016089f 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -295,7 +295,6 @@ static void change_clocksource(void) if (old->disable) old->disable(old); - clock->cycle_last = 0; clock->cycle_last = clock->read(clock); clock->error = 0; clock->xtime_nsec = 0; |