sched_clock: prevent scd->clock from moving backwards

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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>

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Dave Kleikamp 2008-10-09 13:21:30 -05:00 • committed by Ingo Molnar

parent a5d8c3483a

commit 5b7dba4ff8

1 changed files with 3 additions and 3 deletions

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kernel/sched_clock.c

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