Commit a761a67f authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

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: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210713135158.488853478@linutronix.de
parent 66f7b0c8

include/linux/hrtimer.h

+0 −1
Original line number Diff line number Diff line
@@ -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);

kernel/time/hrtimer.c

+6 −9
Original line number Diff line number Diff line
@@ -900,8 +900,8 @@ static void clock_was_set_work(struct work_struct *work) 
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)

{
@@ -909,18 +909,15 @@ 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();

}



/*

kernel/time/tick-common.c

+7 −0
Original line number Diff line number Diff line
@@ -470,6 +470,13 @@ 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();

}



/**

kernel/time/tick-internal.h

+2 −0
Original line number Diff line number Diff line
@@ -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);

kernel/time/timekeeping.c

+3 −1
Original line number Diff line number Diff line
@@ -1810,8 +1810,10 @@ 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)