This notifier will fire when clocksource is changed or
any properties of the clocksource are changed which alter
the clocksource nature, for example its stability property
Signed-off-by: Denis Plotnikov <dplotnikov@xxxxxxxxxxxxx>
---
include/linux/cs_notifier.h | 17 +++++++++++++++
kernel/time/timekeeping.c | 51 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 68 insertions(+)
create mode 100644 include/linux/cs_notifier.h
diff --git a/include/linux/cs_notifier.h b/include/linux/cs_notifier.h
new file mode 100644
index 0000000..2b1b4e6
--- /dev/null
+++ b/include/linux/cs_notifier.h
@@ -0,0 +1,17 @@
+#ifndef _CS_CHANGES_H
+#define _CS_CHANGES_H
+
+#include <linux/notifier.h>
+
+/*
+ * The clocksource changes notifier is called when the system
+ * clocksource is changed or some properties of the current
+ * system clocksource is changed that can affect other parts of the system,
+ * for example KVM guests
+ */
+
+extern void clocksource_changes_notify(void);
+extern int clocksource_changes_register_notifier(struct notifier_block *nb);
+extern int clocksource_changes_unregister_notifier(struct notifier_block *nb);
+
+#endif /* _CS_CHANGES_H */
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index b6d7882..1cef214 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -592,6 +592,55 @@ int pvclock_gtod_unregister_notifier(struct notifier_block *nb)
}
EXPORT_SYMBOL_GPL(pvclock_gtod_unregister_notifier);
+/* notification chain when there is some changes in the clocksource */
+static RAW_NOTIFIER_HEAD(clocksource_changes_chain);
+
+/**
+ * notify_clocksource_changing - notify all the listeners about changes
+ * happened in the clocksource: changing a clocksource, changing the sensitive
+ * parameters of the clocksource, e.g. stability flag for kvmclock
+ */
+void clocksource_changes_notify(void)
+{
+ raw_notifier_call_chain(&clocksource_changes_chain, 0L, NULL);
+}
+EXPORT_SYMBOL_GPL(clocksource_changes_notify);
+
+/**
+ * clocksource_changes_register_notifier - register
+ * a clocksource changes listener
+ */
+int clocksource_changes_register_notifier(struct notifier_block *nb)
+{
+ unsigned long flags;
+ int ret;
+
+ raw_spin_lock_irqsave(&timekeeper_lock, flags);
+ ret = raw_notifier_chain_register(&clocksource_changes_chain, nb);
+ clocksource_changes_notify();
+ raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(clocksource_changes_register_notifier);
+
+/**
+ * clocksource_changes_unregister_notifier - unregister
+ * a clocksource changes listener
+ */
+int clocksource_changes_unregister_notifier(struct notifier_block *nb)
+{
+ unsigned long flags;
+ int ret;
+
+ raw_spin_lock_irqsave(&timekeeper_lock, flags);
+ ret = raw_notifier_chain_unregister(&clocksource_changes_chain, nb);
+ raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(clocksource_changes_unregister_notifier);
+
/*
* tk_update_leap_state - helper to update the next_leap_ktime
*/
@@ -1342,6 +1391,7 @@ static int change_clocksource(void *data)
}
}
timekeeping_update(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);
+ clocksource_changes_notify();
write_seqcount_end(&tk_core.seq);
raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
@@ -1521,6 +1571,7 @@ void __init timekeeping_init(void)
tk_set_wall_to_mono(tk, tmp);
timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
+ clocksource_changes_notify();
write_seqcount_end(&tk_core.seq);
raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
--
2.7.4
