[PATCH] timer cleanups

This is my latest timer patchset, it makes del_timer_sync() a bit more
robust wrt.  code that re-adds timers from the timer handler.

Other changes in the patch:

 - clean up cascading a bit.

 - do not save flags in __run_timer_list - we enter from an irqs-enabled
   tasklet.

kernel/timer.c

@@ -266,29 +266,31 @@ int del_timer(timer_t *timer)
 int del_timer_sync(timer_t *timer)
 {
 	tvec_base_t *base = tvec_bases;
-	int i, ret;
+	int i, ret = 0;
 
-	ret = del_timer(timer);
+del_again:
+	ret += del_timer(timer);
 
-	for (i = 0; i < NR_CPUS; i++) {
+	for (i = 0; i < NR_CPUS; i++, base++) {
 		if (!cpu_online(i))
 			continue;
 		if (base->running_timer == timer) {
 			while (base->running_timer == timer) {
 				cpu_relax();
-				preempt_disable();
-				preempt_enable();
+				preempt_check_resched();
 			}
 			break;
 		}
-		base++;
 	}
+	if (timer_pending(timer))
+		goto del_again;
+
 	return ret;
 }
 #endif
 
 
-static void cascade(tvec_base_t *base, tvec_t *tv)
+static int cascade(tvec_base_t *base, tvec_t *tv)
 {
 	/* cascade all the timers from tv up one level */
 	struct list_head *head, *curr, *next;
@@ -310,7 +312,8 @@ static void cascade(tvec_base_t *base, tvec_t *tv)
 		curr = next;
 	}
 	INIT_LIST_HEAD(head);
-	tv->index = (tv->index + 1) & TVN_MASK;
+
+	return tv->index = (tv->index + 1) & TVN_MASK;
 }
 
 /***
@@ -322,26 +325,18 @@ static void cascade(tvec_base_t *base, tvec_t *tv)
  */
 static inline void __run_timers(tvec_base_t *base)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&base->lock, flags);
+	spin_lock_irq(&base->lock);
 	while ((long)(jiffies - base->timer_jiffies) >= 0) {
 		struct list_head *head, *curr;
 
 		/*
 		 * Cascade timers:
 		 */
-		if (!base->tv1.index) {
-			cascade(base, &base->tv2);
-			if (base->tv2.index == 1) {
-				cascade(base, &base->tv3);
-				if (base->tv3.index == 1) {
-					cascade(base, &base->tv4);
-					if (base->tv4.index == 1)
+		if (!base->tv1.index &&
+			(cascade(base, &base->tv2) == 1) &&
+				(cascade(base, &base->tv3) == 1) &&
+					cascade(base, &base->tv4) == 1)
 			cascade(base, &base->tv5);
-				}
-			}
-		}
 repeat:
 		head = base->tv1.vec + base->tv1.index;
 		curr = head->next;
@@ -360,6 +355,9 @@ static inline void __run_timers(tvec_base_t *base)
 			base->running_timer = timer;
 #endif
 			spin_unlock_irq(&base->lock);
+			if (!fn)
+				printk("Bad: timer %p has NULL fn. (data: %08lx)\n", timer, data);
+			else
 				fn(data);
 			spin_lock_irq(&base->lock);
 			goto repeat;
@@ -370,7 +368,7 @@ static inline void __run_timers(tvec_base_t *base)
 #if CONFIG_SMP
 	base->running_timer = NULL;
 #endif
-	spin_unlock_irqrestore(&base->lock, flags);
+	spin_unlock_irq(&base->lock);
 }
 
 /******************************************************************/