Messages in this thread Patch in this message | | | Date | Tue, 27 Apr 2021 10:25:41 +0200 | From | Thomas Gleixner <> | Subject | [patch 4/8] timekeeping: Distangle resume and clock-was-set events |
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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> --- include/linux/hrtimer.h | 1 - kernel/time/hrtimer.c | 15 ++++++--------- kernel/time/tick-common.c | 7 +++++++ kernel/time/tick-internal.h | 2 ++ kernel/time/timekeeping.c | 4 +++- 5 files changed, 18 insertions(+), 11 deletions(-)
--- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -354,7 +354,6 @@ extern void timerfd_resume(void); static inline void timerfd_clock_was_set(void) { } static inline void timerfd_resume(void) { } #endif -extern void hrtimers_resume(void); DECLARE_PER_CPU(struct tick_device, tick_cpu_device); --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -914,8 +914,8 @@ static void clock_was_set_work(struct wo static DECLARE_WORK(hrtimer_work, clock_was_set_work); /* - * Called from timekeeping and resume code to reprogram the hrtimer - * interrupt device on all cpus and to notify timerfd. + * Called from timekeeping code to reprogram the hrtimer interrupt device + * on all cpus and to notify timerfd. */ void clock_was_set_delayed(void) { @@ -923,18 +923,15 @@ void clock_was_set_delayed(void) } /* - * During resume we might have to reprogram the high resolution timer - * interrupt on all online CPUs. However, all other CPUs will be - * stopped with IRQs interrupts disabled so the clock_was_set() call - * must be deferred. + * Called during resume either directly from via timekeeping_resume() + * or in the case of s2idle from tick_unfreeze() to ensure that the + * hrtimers are up to date. */ -void hrtimers_resume(void) +void hrtimers_resume_local(void) { lockdep_assert_irqs_disabled(); /* Retrigger on the local CPU */ retrigger_next_event(NULL); - /* And schedule a retrigger for all others */ - clock_was_set_delayed(); } /* --- a/kernel/time/tick-common.c +++ b/kernel/time/tick-common.c @@ -475,6 +475,13 @@ void tick_resume_local(void) else tick_resume_oneshot(); } + + /* + * Ensure that hrtimers are up to date and the clockevents device + * is reprogrammed correctly when high resolution timers are + * enabled. + */ + hrtimers_resume_local(); } /** --- a/kernel/time/tick-internal.h +++ b/kernel/time/tick-internal.h @@ -167,3 +167,5 @@ void timer_clear_idle(void); void clock_was_set(void); void clock_was_set_delayed(void); + +void hrtimers_resume_local(void); --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1799,8 +1799,10 @@ void timekeeping_resume(void) touch_softlockup_watchdog(); + /* Resume the clockevent device(s) and hrtimers */ tick_resume(); - hrtimers_resume(); + /* Notify timerfd as resume is equivalent to clock_was_set() */ + timerfd_resume(); } int timekeeping_suspend(void)
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