ARM: fix rcu stalls on SMP platforms

commit 7deabca0 upstream.

We can stall RCU processing on SMP platforms if a CPU sits in its idle
loop for a long time.  This happens because we don't call irq_enter()
and irq_exit() around generic_smp_call_function_interrupt() and
friends.  Add the necessary calls, and remove the one from within
ipi_timer(), so that they're all in a common place.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

arch/arm/kernel/smp.c

@@ -471,9 +471,7 @@ static DEFINE_PER_CPU(struct clock_event_device, percpu_clockevent);
 static void ipi_timer(void)
 {
 	struct clock_event_device *evt = &__get_cpu_var(percpu_clockevent);
-	irq_enter();
 	evt->event_handler(evt);
-	irq_exit();
 }
 
 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
@@ -572,7 +570,9 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
 
 	switch (ipinr) {
 	case IPI_TIMER:
+		irq_enter();
 		ipi_timer();
+		irq_exit();
 		break;
 
 	case IPI_RESCHEDULE:
@@ -580,15 +580,21 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
 		break;
 
 	case IPI_CALL_FUNC:
+		irq_enter();
 		generic_smp_call_function_interrupt();
+		irq_exit();
 		break;
 
 	case IPI_CALL_FUNC_SINGLE:
+		irq_enter();
 		generic_smp_call_function_single_interrupt();
+		irq_exit();
 		break;
 
 	case IPI_CPU_STOP:
+		irq_enter();
 		ipi_cpu_stop(cpu);
+		irq_exit();
 		break;
 
 	default: