timekeeping: Distangle resume and clock-was-set events

Resuming timekeeping is a clock-was-set event and uses the clock-was-set
notification mechanism. This is in the way of making the clock-was-set
update for hrtimers selective so unnecessary IPIs are avoided when a CPU
base does not have timers queued which are affected by the clock setting.

Distangle it by invoking hrtimer_resume() on each unfreezing CPU and invoke
the new timerfd_resume() function from timekeeping_resume() which is the
only place where this is needed.

Rename hrtimer_resume() to hrtimer_resume_local() to reflect the change.

With this the clock_was_set*() functions are not longer required to IPI all
CPUs unconditionally and can get some smarts to avoid them.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210713135158.488853478@linutronix.de

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index cd610faa2523..22de98cc6dd8 100644
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -168,3 +168,5 @@ void timer_clear_idle(void);
 
 void clock_was_set(void);
 void clock_was_set_delayed(void);
+
+void hrtimers_resume_local(void);