From: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Date: Thu, 9 Oct 2008 18:21:30 +0000 (-0500)
Subject: sched_clock: prevent scd->clock from moving backwards
X-Git-Tag: v2.6.28-rc1~267^2^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5b7dba4ff834259a5623e03a565748704a8fe449;p=pandora-kernel.git

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>
---

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