Merge "sched: Add a check for cpu unbound deferrable timers"

include/linux/timer.h

@@ -173,6 +173,9 @@ extern int mod_timer_pending(struct timer_list *timer, unsigned long expires);
 extern int mod_timer_pinned(struct timer_list *timer, unsigned long expires);
 
 extern void set_timer_slack(struct timer_list *time, int slack_hz);
+#ifdef CONFIG_SMP
+extern bool check_pending_deferrable_timers(int cpu);
+#endif
 
 #define TIMER_NOT_PINNED	0
 #define TIMER_PINNED		1

kernel/time/tick-sched.c

@@ -19,6 +19,7 @@
 #include <linux/percpu.h>
 #include <linux/profile.h>
 #include <linux/sched.h>
+#include <linux/timer.h>
 #include <linux/module.h>
 #include <linux/irq_work.h>
 #include <linux/posix-timers.h>
@@ -809,6 +810,11 @@ static void __tick_nohz_idle_enter(struct tick_sched *ts)
 
 	now = tick_nohz_start_idle(ts);
 
+#ifdef CONFIG_SMP
+	if (check_pending_deferrable_timers(cpu))
+		raise_softirq_irqoff(TIMER_SOFTIRQ);
+#endif
+
 	if (can_stop_idle_tick(cpu, ts)) {
 		int was_stopped = ts->tick_stopped;
 

kernel/time/timer.c

@@ -102,6 +102,7 @@ static DEFINE_PER_CPU(struct tvec_base, tvec_bases);
 unsigned int sysctl_timer_migration = 1;
 
 struct tvec_base tvec_base_deferrable;
+static atomic_t deferrable_pending;
 
 void timers_update_migration(bool update_nohz)
 {
@@ -150,9 +151,12 @@ static inline struct tvec_base *get_target_base(struct tvec_base *base,
 
 static inline void __run_deferrable_timers(void)
 {
-	if (smp_processor_id() == tick_do_timer_cpu &&
-	    time_after_eq(jiffies, tvec_base_deferrable.timer_jiffies))
-		__run_timers(&tvec_base_deferrable);
+	if (time_after_eq(jiffies, tvec_base_deferrable.timer_jiffies)) {
+		if ((atomic_cmpxchg(&deferrable_pending, 1, 0) &&
+			tick_do_timer_cpu == TICK_DO_TIMER_NONE) ||
+			tick_do_timer_cpu == smp_processor_id())
+			__run_timers(&tvec_base_deferrable);
+	}
 }
 
 static inline void init_timer_deferrable_global(void)
@@ -1428,6 +1432,30 @@ 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, tvec_base_deferrable.timer_jiffies)
+			&& !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