1 files changed, 67 insertions, 35 deletions

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 152a706ef8b8..f2674a056c26 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -195,7 +195,7 @@ EXPORT_SYMBOL(jiffies_64);
 #endif
 
 struct timer_base {
-	spinlock_t		lock;
+	raw_spinlock_t		lock;
 	struct timer_list	*running_timer;
 	unsigned long		clk;
 	unsigned long		next_expiry;
@@ -203,6 +203,7 @@ struct timer_base {
 	bool			migration_enabled;
 	bool			nohz_active;
 	bool			is_idle;
+	bool			must_forward_clk;
 	DECLARE_BITMAP(pending_map, WHEEL_SIZE);
 	struct hlist_head	vectors[WHEEL_SIZE];
 } ____cacheline_aligned;
@@ -856,13 +857,19 @@ get_target_base(struct timer_base *base, unsigned tflags)
 
 static inline void forward_timer_base(struct timer_base *base)
 {
-	unsigned long jnow = READ_ONCE(jiffies);
+	unsigned long jnow;
 
 	/*
-	 * We only forward the base when it's idle and we have a delta between
-	 * base clock and jiffies.
+	 * We only forward the base when we are idle or have just come out of
+	 * idle (must_forward_clk logic), and have a delta between base clock
+	 * and jiffies. In the common case, run_timers will take care of it.
 	 */
-	if (!base->is_idle || (long) (jnow - base->clk) < 2)
+	if (likely(!base->must_forward_clk))
+		return;
+
+	jnow = READ_ONCE(jiffies);
+	base->must_forward_clk = base->is_idle;
+	if ((long)(jnow - base->clk) < 2)
 		return;
 
 	/*
@@ -913,10 +920,10 @@ static struct timer_base *lock_timer_base(struct timer_list *timer,
 
 		if (!(tf & TIMER_MIGRATING)) {
 			base = get_timer_base(tf);
-			spin_lock_irqsave(&base->lock, *flags);
+			raw_spin_lock_irqsave(&base->lock, *flags);
 			if (timer->flags == tf)
 				return base;
-			spin_unlock_irqrestore(&base->lock, *flags);
+			raw_spin_unlock_irqrestore(&base->lock, *flags);
 		}
 		cpu_relax();
 	}
@@ -938,6 +945,11 @@ __mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only)
 	 * same array bucket then just return:
 	 */
 	if (timer_pending(timer)) {
+		/*
+		 * The downside of this optimization is that it can result in
+		 * larger granularity than you would get from adding a new
+		 * timer with this expiry.
+		 */
 		if (timer->expires == expires)
 			return 1;
 
@@ -948,6 +960,7 @@ __mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only)
 		 * dequeue/enqueue dance.
 		 */
 		base = lock_timer_base(timer, &flags);
+		forward_timer_base(base);
 
 		clk = base->clk;
 		idx = calc_wheel_index(expires, clk);
@@ -964,6 +977,7 @@ __mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only)
 		}
 	} else {
 		base = lock_timer_base(timer, &flags);
+		forward_timer_base(base);
 	}
 
 	ret = detach_if_pending(timer, base, false);
@@ -986,17 +1000,15 @@ __mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only)
 			/* See the comment in lock_timer_base() */
 			timer->flags |= TIMER_MIGRATING;
 
-			spin_unlock(&base->lock);
+			raw_spin_unlock(&base->lock);
 			base = new_base;
-			spin_lock(&base->lock);
+			raw_spin_lock(&base->lock);
 			WRITE_ONCE(timer->flags,
 				   (timer->flags & ~TIMER_BASEMASK) | base->cpu);
+			forward_timer_base(base);
 		}
 	}
 
-	/* Try to forward a stale timer base clock */
-	forward_timer_base(base);
-
 	timer->expires = expires;
 	/*
 	 * If 'idx' was calculated above and the base time did not advance
@@ -1013,7 +1025,7 @@ __mod_timer(struct timer_list *timer, unsigned long expires, bool pending_only)
 	}
 
 out_unlock:
-	spin_unlock_irqrestore(&base->lock, flags);
+	raw_spin_unlock_irqrestore(&base->lock, flags);
 
 	return ret;
 }
@@ -1106,16 +1118,17 @@ void add_timer_on(struct timer_list *timer, int cpu)
 	if (base != new_base) {
 		timer->flags |= TIMER_MIGRATING;
 
-		spin_unlock(&base->lock);
+		raw_spin_unlock(&base->lock);
 		base = new_base;
-		spin_lock(&base->lock);
+		raw_spin_lock(&base->lock);
 		WRITE_ONCE(timer->flags,
 			   (timer->flags & ~TIMER_BASEMASK) | cpu);
 	}
+	forward_timer_base(base);
 
 	debug_activate(timer, timer->expires);
 	internal_add_timer(base, timer);
-	spin_unlock_irqrestore(&base->lock, flags);
+	raw_spin_unlock_irqrestore(&base->lock, flags);
 }
 EXPORT_SYMBOL_GPL(add_timer_on);
 
@@ -1141,7 +1154,7 @@ int del_timer(struct timer_list *timer)
 	if (timer_pending(timer)) {
 		base = lock_timer_base(timer, &flags);
 		ret = detach_if_pending(timer, base, true);
-		spin_unlock_irqrestore(&base->lock, flags);
+		raw_spin_unlock_irqrestore(&base->lock, flags);
 	}
 
 	return ret;
@@ -1150,7 +1163,7 @@ EXPORT_SYMBOL(del_timer);
 
 /**
  * try_to_del_timer_sync - Try to deactivate a timer
- * @timer: timer do del
+ * @timer: timer to delete
  *
  * This function tries to deactivate a timer. Upon successful (ret >= 0)
  * exit the timer is not queued and the handler is not running on any CPU.
@@ -1168,7 +1181,7 @@ int try_to_del_timer_sync(struct timer_list *timer)
 	if (base->running_timer != timer)
 		ret = detach_if_pending(timer, base, true);
 
-	spin_unlock_irqrestore(&base->lock, flags);
+	raw_spin_unlock_irqrestore(&base->lock, flags);
 
 	return ret;
 }
@@ -1299,13 +1312,13 @@ static void expire_timers(struct timer_base *base, struct hlist_head *head)
 		data = timer->data;
 
 		if (timer->flags & TIMER_IRQSAFE) {
-			spin_unlock(&base->lock);
+			raw_spin_unlock(&base->lock);
 			call_timer_fn(timer, fn, data);
-			spin_lock(&base->lock);
+			raw_spin_lock(&base->lock);
 		} else {
-			spin_unlock_irq(&base->lock);
+			raw_spin_unlock_irq(&base->lock);
 			call_timer_fn(timer, fn, data);
-			spin_lock_irq(&base->lock);
+			raw_spin_lock_irq(&base->lock);
 		}
 	}
 }
@@ -1474,7 +1487,7 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
 	if (cpu_is_offline(smp_processor_id()))
 		return expires;
 
-	spin_lock(&base->lock);
+	raw_spin_lock(&base->lock);
 	nextevt = __next_timer_interrupt(base);
 	is_max_delta = (nextevt == base->clk + NEXT_TIMER_MAX_DELTA);
 	base->next_expiry = nextevt;
@@ -1495,14 +1508,20 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
 		base->is_idle = false;
 	} else {
 		if (!is_max_delta)
-			expires = basem + (nextevt - basej) * TICK_NSEC;
+			expires = basem + (u64)(nextevt - basej) * TICK_NSEC;
 		/*
-		 * If we expect to sleep more than a tick, mark the base idle:
+		 * If we expect to sleep more than a tick, mark the base idle.
+		 * Also the tick is stopped so any added timer must forward
+		 * the base clk itself to keep granularity small. This idle
+		 * logic is only maintained for the BASE_STD base, deferrable
+		 * timers may still see large granularity skew (by design).
 		 */
-		if ((expires - basem) > TICK_NSEC)
+		if ((expires - basem) > TICK_NSEC) {
+			base->must_forward_clk = true;
 			base->is_idle = true;
+		}
 	}
-	spin_unlock(&base->lock);
+	raw_spin_unlock(&base->lock);
 
 	return cmp_next_hrtimer_event(basem, expires);
 }
@@ -1590,7 +1609,7 @@ static inline void __run_timers(struct timer_base *base)
 	if (!time_after_eq(jiffies, base->clk))
 		return;
 
-	spin_lock_irq(&base->lock);
+	raw_spin_lock_irq(&base->lock);
 
 	while (time_after_eq(jiffies, base->clk)) {
 
@@ -1601,7 +1620,7 @@ static inline void __run_timers(struct timer_base *base)
 			expire_timers(base, heads + levels);
 	}
 	base->running_timer = NULL;
-	spin_unlock_irq(&base->lock);
+	raw_spin_unlock_irq(&base->lock);
 }
 
 /*
@@ -1611,6 +1630,19 @@ static __latent_entropy void run_timer_softirq(struct softirq_action *h)
 {
 	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
 
+	/*
+	 * must_forward_clk must be cleared before running timers so that any
+	 * timer functions that call mod_timer will not try to forward the
+	 * base. idle trcking / clock forwarding logic is only used with
+	 * BASE_STD timers.
+	 *
+	 * The deferrable base does not do idle tracking at all, so we do
+	 * not forward it. This can result in very large variations in
+	 * granularity for deferrable timers, but they can be deferred for
+	 * long periods due to idle.
+	 */
+	base->must_forward_clk = false;
+
 	__run_timers(base);
 	if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && base->nohz_active)
 		__run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
@@ -1786,16 +1818,16 @@ int timers_dead_cpu(unsigned int cpu)
 		 * The caller is globally serialized and nobody else
 		 * takes two locks at once, deadlock is not possible.
 		 */
-		spin_lock_irq(&new_base->lock);
-		spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
+		raw_spin_lock_irq(&new_base->lock);
+		raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
 
 		BUG_ON(old_base->running_timer);
 
 		for (i = 0; i < WHEEL_SIZE; i++)
 			migrate_timer_list(new_base, old_base->vectors + i);
 
-		spin_unlock(&old_base->lock);
-		spin_unlock_irq(&new_base->lock);
+		raw_spin_unlock(&old_base->lock);
+		raw_spin_unlock_irq(&new_base->lock);
 		put_cpu_ptr(&timer_bases);
 	}
 	return 0;
@@ -1811,7 +1843,7 @@ static void __init init_timer_cpu(int cpu)
 	for (i = 0; i < NR_BASES; i++) {
 		base = per_cpu_ptr(&timer_bases[i], cpu);
 		base->cpu = cpu;
-		spin_lock_init(&base->lock);
+		raw_spin_lock_init(&base->lock);
 		base->clk = jiffies;
 	}
 }