X-Git-Url: http://pilppa.org/gitweb/gitweb.cgi?a=blobdiff_plain;f=kernel%2Ftime%2Ftick-sched.c;h=b416995b975727ca8b6dbf8b331de5351a1ef7f5;hb=d6dd9e93c7531fa31370e27d053a3940d8d662fb;hp=51556b95f60f0db395cd7cdaf6a840479625fe1c;hpb=5992fd1995a5e69710011fc7d7945c62bf5b551b;p=linux-2.6-omap-h63xx.git

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 51556b95f60..b416995b975 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -167,9 +167,15 @@ void tick_nohz_stop_sched_tick(void)
 		goto end;
 
 	cpu = smp_processor_id();
-	if (unlikely(local_softirq_pending()))
-		printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n",
-		       local_softirq_pending());
+	if (unlikely(local_softirq_pending())) {
+		static int ratelimit;
+
+		if (ratelimit < 10) {
+			printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n",
+			       local_softirq_pending());
+			ratelimit++;
+		}
+	}
 
 	now = ktime_get();
 	/*
@@ -217,10 +223,45 @@ void tick_nohz_stop_sched_tick(void)
 		 * the scheduler tick in nohz_restart_sched_tick.
 		 */
 		if (!ts->tick_stopped) {
+			if (select_nohz_load_balancer(1)) {
+				/*
+				 * sched tick not stopped!
+				 */
+				cpu_clear(cpu, nohz_cpu_mask);
+				goto out;
+			}
+
 			ts->idle_tick = ts->sched_timer.expires;
 			ts->tick_stopped = 1;
 			ts->idle_jiffies = last_jiffies;
 		}
+
+		/*
+		 * If this cpu is the one which updates jiffies, then
+		 * give up the assignment and let it be taken by the
+		 * cpu which runs the tick timer next, which might be
+		 * this cpu as well. If we don't drop this here the
+		 * jiffies might be stale and do_timer() never
+		 * invoked.
+		 */
+		if (cpu == tick_do_timer_cpu)
+			tick_do_timer_cpu = -1;
+
+		ts->idle_sleeps++;
+
+		/*
+		 * delta_jiffies >= NEXT_TIMER_MAX_DELTA signals that
+		 * there is no timer pending or at least extremly far
+		 * into the future (12 days for HZ=1000). In this case
+		 * we simply stop the tick timer:
+		 */
+		if (unlikely(delta_jiffies >= NEXT_TIMER_MAX_DELTA)) {
+			ts->idle_expires.tv64 = KTIME_MAX;
+			if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
+				hrtimer_cancel(&ts->sched_timer);
+			goto out;
+		}
+
 		/*
 		 * calculate the expiry time for the next timer wheel
 		 * timer
@@ -228,7 +269,6 @@ void tick_nohz_stop_sched_tick(void)
 		expires = ktime_add_ns(last_update, tick_period.tv64 *
 				       delta_jiffies);
 		ts->idle_expires = expires;
-		ts->idle_sleeps++;
 
 		if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
 			hrtimer_start(&ts->sched_timer, expires,
@@ -273,6 +313,7 @@ void tick_nohz_restart_sched_tick(void)
 	now = ktime_get();
 
 	local_irq_disable();
+	select_nohz_load_balancer(0);
 	tick_do_update_jiffies64(now);
 	cpu_clear(cpu, nohz_cpu_mask);
 
@@ -338,12 +379,24 @@ static void tick_nohz_handler(struct clock_event_device *dev)
 {
 	struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
 	struct pt_regs *regs = get_irq_regs();
+	int cpu = smp_processor_id();
 	ktime_t now = ktime_get();
 
 	dev->next_event.tv64 = KTIME_MAX;
 
+	/*
+	 * Check if the do_timer duty was dropped. We don't care about
+	 * concurrency: This happens only when the cpu in charge went
+	 * into a long sleep. If two cpus happen to assign themself to
+	 * this duty, then the jiffies update is still serialized by
+	 * xtime_lock.
+	 */
+	if (unlikely(tick_do_timer_cpu == -1))
+		tick_do_timer_cpu = cpu;
+
 	/* Check, if the jiffies need an update */
-	tick_do_update_jiffies64(now);
+	if (tick_do_timer_cpu == cpu)
+		tick_do_update_jiffies64(now);
 
 	/*
 	 * When we are idle and the tick is stopped, we have to touch
@@ -431,9 +484,23 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
 	struct hrtimer_cpu_base *base = timer->base->cpu_base;
 	struct pt_regs *regs = get_irq_regs();
 	ktime_t now = ktime_get();
+	int cpu = smp_processor_id();
+
+#ifdef CONFIG_NO_HZ
+	/*
+	 * Check if the do_timer duty was dropped. We don't care about
+	 * concurrency: This happens only when the cpu in charge went
+	 * into a long sleep. If two cpus happen to assign themself to
+	 * this duty, then the jiffies update is still serialized by
+	 * xtime_lock.
+	 */
+	if (unlikely(tick_do_timer_cpu == -1))
+		tick_do_timer_cpu = cpu;
+#endif
 
 	/* Check, if the jiffies need an update */
-	tick_do_update_jiffies64(now);
+	if (tick_do_timer_cpu == cpu)
+		tick_do_update_jiffies64(now);
 
 	/*
 	 * Do not call, when we are not in irq context and have
@@ -479,6 +546,7 @@ void tick_setup_sched_timer(void)
 {
 	struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
 	ktime_t now = ktime_get();
+	u64 offset;
 
 	/*
 	 * Emulate tick processing via per-CPU hrtimers:
@@ -487,8 +555,12 @@ void tick_setup_sched_timer(void)
 	ts->sched_timer.function = tick_sched_timer;
 	ts->sched_timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_SOFTIRQ;
 
-	/* Get the next period */
+	/* Get the next period (per cpu) */
 	ts->sched_timer.expires = tick_init_jiffy_update();
+	offset = ktime_to_ns(tick_period) >> 1;
+	do_div(offset, NR_CPUS);
+	offset *= smp_processor_id();
+	ts->sched_timer.expires = ktime_add_ns(ts->sched_timer.expires, offset);
 
 	for (;;) {
 		hrtimer_forward(&ts->sched_timer, now, tick_period);