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timekeeping: Indicate that clock was set in the pvclock gtod notifier

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If the clock was set (stepped), set the action parameter to functions
in the pvclock gtod notifier chain to non-zero.  This allows the
callee to only do work if the clock was stepped.

This will be used on Xen as the synchronization of the Xen wallclock
to the control domain's (dom0) system time will be done with this
notifier and updating on every timer tick is unnecessary and too
expensive.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: <xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/1372329348-20841-4-git-send-email-david.vrabel@citrix.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
David Vrabel
2013-06-27 11:35:46 +01:00
committed by Thomas Gleixner
parent 04397fe94a
commit 780427f0e1
2 changed files with 25 additions and 12 deletions
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7
include/linux/pvclock_gtod.h
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@@ -3,6 +3,13 @@
#include <linux/notifier.h>
/*
* The pvclock gtod notifier is called when the system time is updated
* and is used to keep guest time synchronized with host time.
*
* The 'action' parameter in the notifier function is false (0), or
* true (non-zero) if system time was stepped.
*/
extern int pvclock_gtod_register_notifier(struct notifier_block *nb);
extern int pvclock_gtod_unregister_notifier(struct notifier_block *nb);