Merge branch 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  timers: handle HRTIMER_CB_IRQSAFE_UNLOCKED correctly from softirq context
  nohz: disable tick_nohz_kick_tick() for now
  irq: call __irq_enter() before calling the tick_idle_check
  x86: HPET: enter hpet_interrupt_handler with interrupts disabled
  x86: HPET: read from HPET_Tn_CMP() not HPET_T0_CMP
  x86: HPET: convert WARN_ON to WARN_ON_ONCE

Author: torvalds

arch/x86/kernel/hpet.c

@@ -322,7 +322,7 @@ static int hpet_next_event(unsigned long delta,
 	 * what we wrote hit the chip before we compare it to the
 	 * counter.
 	 */
-	WARN_ON((u32)hpet_readl(HPET_T0_CMP) != cnt);
+	WARN_ON_ONCE((u32)hpet_readl(HPET_Tn_CMP(timer)) != cnt);
 
 	return (s32)((u32)hpet_readl(HPET_COUNTER) - cnt) >= 0 ? -ETIME : 0;
 }
@@ -445,7 +445,7 @@ static int hpet_setup_irq(struct hpet_dev *dev)
 {
 
 	if (request_irq(dev->irq, hpet_interrupt_handler,
-			IRQF_SHARED|IRQF_NOBALANCING, dev->name, dev))
+			IRQF_DISABLED|IRQF_NOBALANCING, dev->name, dev))
 		return -1;
 
 	disable_irq(dev->irq);

kernel/hrtimer.c

@@ -1209,6 +1209,7 @@ static void run_hrtimer_pending(struct hrtimer_cpu_base *cpu_base)
 		enum hrtimer_restart (*fn)(struct hrtimer *);
 		struct hrtimer *timer;
 		int restart;
+		int emulate_hardirq_ctx = 0;
 
 		timer = list_entry(cpu_base->cb_pending.next,
 				   struct hrtimer, cb_entry);
@@ -1217,10 +1218,24 @@ static void run_hrtimer_pending(struct hrtimer_cpu_base *cpu_base)
 		timer_stats_account_hrtimer(timer);
 
 		fn = timer->function;
+		/*
+		 * A timer might have been added to the cb_pending list
+		 * when it was migrated during a cpu-offline operation.
+		 * Emulate hardirq context for such timers.
+		 */
+		if (timer->cb_mode == HRTIMER_CB_IRQSAFE_PERCPU ||
+		    timer->cb_mode == HRTIMER_CB_IRQSAFE_UNLOCKED)
+			emulate_hardirq_ctx = 1;
+
 		__remove_hrtimer(timer, timer->base, HRTIMER_STATE_CALLBACK, 0);
 		spin_unlock_irq(&cpu_base->lock);
 
-		restart = fn(timer);
+		if (unlikely(emulate_hardirq_ctx)) {
+			local_irq_disable();
+			restart = fn(timer);
+			local_irq_enable();
+		} else
+			restart = fn(timer);
 
 		spin_lock_irq(&cpu_base->lock);
 

kernel/softirq.c

@@ -269,10 +269,11 @@ void irq_enter(void)
 {
 	int cpu = smp_processor_id();
 
-	if (idle_cpu(cpu) && !in_interrupt())
+	if (idle_cpu(cpu) && !in_interrupt()) {
+		__irq_enter();
 		tick_check_idle(cpu);
-
-	__irq_enter();
+	} else
+		__irq_enter();
 }
 
 #ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED

kernel/time/tick-sched.c

@@ -568,6 +568,9 @@ static void tick_nohz_switch_to_nohz(void)
  */
 static void tick_nohz_kick_tick(int cpu)
 {
+#if 0
+	/* Switch back to 2.6.27 behaviour */
+
 	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
 	ktime_t delta, now;
 
@@ -584,6 +587,7 @@ static void tick_nohz_kick_tick(int cpu)
 		return;
 
 	tick_nohz_restart(ts, now);
+#endif
 }
 
 #else