[PATCH] Extend next_timer_interrupt() to use a reference jiffie

For CONFIG_NO_HZ we need to calculate the next timer wheel event based on a given jiffie value. Extend the existing code to allow the extra 'now' argument. Provide a compability function for the existing implementations to call the function with now == jiffies. (This also solves the racyness of the original code vs. jiffies changing during the iteration.) No functional changes to existing users of this infrastructure. [ remove WARN_ON() that triggered on s390, by Carsten Otte <cotte@de.ibm.com> ] [ made new helper static, Adrian Bunk <bunk@stusta.de> ] Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: john stultz <johnstul@us.ibm.com> Cc: Roman Zippel <zippel@linux-m68k.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

[PATCH] Extend next_timer_interrupt() to use a reference jiffie
For CONFIG_NO_HZ we need to calculate the next timer wheel event based on a given jiffie value. Extend the existing code to allow the extra 'now' argument. Provide a compability function for the existing implementations to call the function with now == jiffies. (This also solves the racyness of the original code vs. jiffies changing during the iteration.) No functional changes to existing users of this infrastructure. [ remove WARN_ON() that triggered on s390, by Carsten Otte <cotte@de.ibm.com> ] [ made new helper static, Adrian Bunk <bunk@stusta.de> ] Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: john stultz <johnstul@us.ibm.com> Cc: Roman Zippel <zippel@linux-m68k.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Thomas Gleixner · Linus Torvalds
1 parent 1cfd68496e
Showing 3 changed files with 22 additions and 4 deletions Side-by-side Diff
include/linux/timer.h
kernel/hrtimer.c
kernel/timer.c
@@ -61,7 +61,17 @@
 extern int __mod_timer(struct timer_list *timer, unsigned long expires);
 extern int mod_timer(struct timer_list *timer, unsigned long expires);
  
+/*
+ * Return when the next timer-wheel timeout occurs (in absolute jiffies),
+ * locks the timer base:
+ */
 extern unsigned long next_timer_interrupt(void);
+/*
+ * Return when the next timer-wheel timeout occurs (in absolute jiffies),
+ * locks the timer base and does the comparison against the given
+ * jiffie.
+ */
+extern unsigned long get_next_timer_interrupt(unsigned long now);
  
 /**
  * add_timer - start a timer
@@ -533,7 +533,7 @@
 }
 EXPORT_SYMBOL_GPL(hrtimer_get_remaining);
  
-#ifdef CONFIG_NO_IDLE_HZ
+#if defined(CONFIG_NO_IDLE_HZ) || defined(CONFIG_NO_HZ)
 /**
  * hrtimer_get_next_event - get the time until next expiry event
  *
@@ -591,7 +591,7 @@
 	spin_unlock_irq(&base->lock);
 }
  
-#ifdef CONFIG_NO_IDLE_HZ
+#if defined(CONFIG_NO_IDLE_HZ) || defined(CONFIG_NO_HZ)
 /*
  * Find out when the next timer event is due to happen. This
  * is used on S/390 to stop all activity when a cpus is idle.
  
@@ -687,10 +687,10 @@
 /**
  * next_timer_interrupt - return the jiffy of the next pending timer
  */
-unsigned long next_timer_interrupt(void)
+unsigned long get_next_timer_interrupt(unsigned long now)
 {
 	tvec_base_t *base = __get_cpu_var(tvec_bases);
-	unsigned long expires, now = jiffies;
+	unsigned long expires;
  
 	spin_lock(&base->lock);
 	expires = __next_timer_interrupt(base);
@@ -701,6 +701,14 @@
  
 	return cmp_next_hrtimer_event(now, expires);
 }
+
+#ifdef CONFIG_NO_IDLE_HZ
+unsigned long next_timer_interrupt(void)
+{
+	return get_next_timer_interrupt(jiffies);
+}
+#endif
+
 #endif
  
 /******************************************************************/
...	...	@@ -61,7 +61,17 @@
61	61	extern int __mod_timer(struct timer_list *timer, unsigned long expires);
62	62	extern int mod_timer(struct timer_list *timer, unsigned long expires);
63	63
	64	+/*
	65	+ * Return when the next timer-wheel timeout occurs (in absolute jiffies),
	66	+ * locks the timer base:
	67	+ */
64	68	extern unsigned long next_timer_interrupt(void);
	69	+/*
	70	+ * Return when the next timer-wheel timeout occurs (in absolute jiffies),
	71	+ * locks the timer base and does the comparison against the given
	72	+ * jiffie.
	73	+ */
	74	+extern unsigned long get_next_timer_interrupt(unsigned long now);
65	75
66	76	/**
67	77	* add_timer - start a timer
...	...	@@ -533,7 +533,7 @@
533	533	}
534	534	EXPORT_SYMBOL_GPL(hrtimer_get_remaining);
535	535
536		-#ifdef CONFIG_NO_IDLE_HZ
	536	+#if defined(CONFIG_NO_IDLE_HZ) \|\| defined(CONFIG_NO_HZ)
537	537	/**
538	538	* hrtimer_get_next_event - get the time until next expiry event
539	539	*
...	...	@@ -591,7 +591,7 @@
591	591	spin_unlock_irq(&base->lock);
592	592	}
593	593
594		-#ifdef CONFIG_NO_IDLE_HZ
	594	+#if defined(CONFIG_NO_IDLE_HZ) \|\| defined(CONFIG_NO_HZ)
595	595	/*
596	596	* Find out when the next timer event is due to happen. This
597	597	* is used on S/390 to stop all activity when a cpus is idle.
598	598
...	...	@@ -687,10 +687,10 @@
687	687	/**
688	688	* next_timer_interrupt - return the jiffy of the next pending timer
689	689	*/
690		-unsigned long next_timer_interrupt(void)
	690	+unsigned long get_next_timer_interrupt(unsigned long now)
691	691	{
692	692	tvec_base_t *base = __get_cpu_var(tvec_bases);
693		- unsigned long expires, now = jiffies;
	693	+ unsigned long expires;
694	694
695	695	spin_lock(&base->lock);
696	696	expires = __next_timer_interrupt(base);
...	...	@@ -701,6 +701,14 @@
701	701
702	702	return cmp_next_hrtimer_event(now, expires);
703	703	}
	704	+
	705	+#ifdef CONFIG_NO_IDLE_HZ
	706	+unsigned long next_timer_interrupt(void)
	707	+{
	708	+ return get_next_timer_interrupt(jiffies);
	709	+}
	710	+#endif
	711	+
704	712	#endif
705	713
706	714	/******************************************************************/