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Commit 1244fa1f authored by Prasad Sodagudi's avatar Prasad Sodagudi Committed by Gerrit - the friendly Code Review server
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sched: Add a check for cpu unbound deferrable timers 



Add a check for cpu unbound deferrable timer expiry and raise
softirq for handling the expired timers so that the CPU can
process the cpu unbound deferrable times as early as possible
when a cpu tries to enter/exit idle loop.

Change-Id: Ieffa74fa22a4d25493f5590b5ac1e0d784fcbbad
Signed-off-by: default avatarPrasad Sodagudi <psodagud@codeaurora.org>
[rishabhb@codeaurora.org: Resolved conflicts due to addition of
commit: time: tick-sched: Reorganize idle tick management code]
Signed-off-by: default avatarRishabh Bhatnagar <rishabhb@codeaurora.org>
parent 13bd9a4c

include/linux/timer.h

+3 −0
Original line number Diff line number Diff line
@@ -161,6 +161,9 @@ extern int del_timer(struct timer_list * timer); 
extern int mod_timer(struct timer_list *timer, unsigned long expires);

extern int mod_timer_pending(struct timer_list *timer, unsigned long expires);

extern int timer_reduce(struct timer_list *timer, unsigned long expires);

#ifdef CONFIG_SMP

extern bool check_pending_deferrable_timers(int cpu);

#endif



/*

 * The jiffies value which is added to now, when there is no timer

kernel/time/tick-sched.c

+6 −0
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ 
#include <linux/module.h>

#include <linux/irq_work.h>

#include <linux/posix-timers.h>

#include <linux/timer.h>

#include <linux/context_tracking.h>

#include <linux/mm.h>
@@ -920,6 +921,11 @@ static void __tick_nohz_idle_stop_tick(struct tick_sched *ts) 
	ktime_t expires;

	int cpu = smp_processor_id();



#ifdef CONFIG_SMP

	if (check_pending_deferrable_timers(cpu))

		raise_softirq_irqoff(TIMER_SOFTIRQ);

#endif



	/*

	 * If tick_nohz_get_sleep_length() ran tick_nohz_next_event(), the

	 * tick timer expiration time is known already.

kernel/time/timer.c

+31 −1
Original line number Diff line number Diff line
@@ -208,6 +208,7 @@ struct timer_base { 


static DEFINE_PER_CPU(struct timer_base, timer_bases[NR_BASES]);

struct timer_base timer_base_deferrable;

static atomic_t deferrable_pending;



#ifdef CONFIG_NO_HZ_COMMON
@@ -1526,6 +1527,31 @@ static u64 cmp_next_hrtimer_event(u64 basem, u64 expires) 
	return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC;

}





#ifdef CONFIG_SMP

/*

 * check_pending_deferrable_timers - Check for unbound deferrable timer expiry

 * @cpu - Current CPU

 *

 * The function checks whether any global deferrable pending timers

 * are exipired or not. This function does not check cpu bounded

 * diferrable pending timers expiry.

 *

 * The function returns true when a cpu unbounded deferrable timer is expired.

 */

bool check_pending_deferrable_timers(int cpu)

{

	if (cpu == tick_do_timer_cpu ||

		tick_do_timer_cpu == TICK_DO_TIMER_NONE) {

		if (time_after_eq(jiffies, timer_base_deferrable.clk)

			&& !atomic_cmpxchg(&deferrable_pending, 0, 1)) {

			return true;

		}

	}

	return false;

}

#endif



/**

 * get_next_timer_interrupt - return the time (clock mono) of the next timer

 * @basej:	base time jiffies
@@ -1712,9 +1738,13 @@ static __latent_entropy void run_timer_softirq(struct softirq_action *h) 


	__run_timers(base);

	if (IS_ENABLED(CONFIG_NO_HZ_COMMON)) {

		__run_timers(&timer_base_deferrable);

		__run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));

	}



	if ((atomic_cmpxchg(&deferrable_pending, 1, 0) &&

		tick_do_timer_cpu == TICK_DO_TIMER_NONE) ||

		tick_do_timer_cpu == smp_processor_id())

		__run_timers(&timer_base_deferrable);

}



/*