diff options
| author | Dave Kleikamp <shaggy@linux.vnet.ibm.com> | 2008-10-26 18:20:14 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2008-11-06 19:05:50 -0800 |
| commit | 5e55aa8db085dad1aabb4574c73c23c7ae571e7b (patch) | |
| tree | 7a22ee8f6d5674b19ab19e64be8f499e17ffe632 | |
| parent | 612f39d5e7baeb0518cfe50d53e37e14c0ca1475 (diff) | |
sched_clock: prevent scd->clock from moving backwards
commit 5b7dba4ff834259a5623e03a565748704a8fe449 upstream
sched_clock: prevent scd->clock from moving backwards
When sched_clock_cpu() couples the clocks between two cpus, it may
increment scd->clock beyond the GTOD tick window that __update_sched_clock()
uses to clamp the clock. A later call to __update_sched_clock() may move
the clock back to scd->tick_gtod + TICK_NSEC, violating the clock's
monotonic property.
This patch ensures that scd->clock will not be set backward.
Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | kernel/sched_clock.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c index e8ab096ddfe3..81787248b60f 100644 --- a/kernel/sched_clock.c +++ b/kernel/sched_clock.c @@ -118,13 +118,13 @@ static u64 __update_sched_clock(struct sched_clock_data *scd, u64 now) /* * scd->clock = clamp(scd->tick_gtod + delta, - * max(scd->tick_gtod, scd->clock), - * scd->tick_gtod + TICK_NSEC); + * max(scd->tick_gtod, scd->clock), + * max(scd->clock, scd->tick_gtod + TICK_NSEC)); */ clock = scd->tick_gtod + delta; min_clock = wrap_max(scd->tick_gtod, scd->clock); - max_clock = scd->tick_gtod + TICK_NSEC; + max_clock = wrap_max(scd->clock, scd->tick_gtod + TICK_NSEC); clock = wrap_max(clock, min_clock); clock = wrap_min(clock, max_clock); |