summaryrefslogtreecommitdiff
path: root/include/linux/pvclock_gtod.h
diff options
context:
space:
mode:
authorDavid Vrabel <david.vrabel@citrix.com>2013-06-27 14:35:46 +0400
committerThomas Gleixner <tglx@linutronix.de>2013-06-29 01:15:06 +0400
commit780427f0e113b4c77dfff4d258c05a902cdb0eb9 (patch)
tree778bc50cbd83b67bdd6ae580a192c4c65e9711bd /include/linux/pvclock_gtod.h
parent04397fe94ad65289884b9862b6a0c722ececaadf (diff)
downloadlinux-780427f0e113b4c77dfff4d258c05a902cdb0eb9.tar.xz
timekeeping: Indicate that clock was set in the pvclock gtod notifier
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>
Diffstat (limited to 'include/linux/pvclock_gtod.h')
-rw-r--r--include/linux/pvclock_gtod.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/include/linux/pvclock_gtod.h b/include/linux/pvclock_gtod.h
index 0ca75825b60d..a71d2dbd3610 100644
--- a/include/linux/pvclock_gtod.h
+++ b/include/linux/pvclock_gtod.h
@@ -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);