From: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Date: Sun, 26 Oct 2008 22:20:14 +0000 (-0400)
Subject: sched_clock: prevent scd->clock from moving backwards
X-Git-Tag: v2.6.27.5~19
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5e55aa8db085dad1aabb4574c73c23c7ae571e7b;p=pandora-kernel.git

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>
---

Reading git-diff-tree failed