[ 28/48] ARM: fix rcu stalls on SMP platforms

[Ben Hutchings]

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>

commit 7deabca0acfe02b8e18f59a4c95676012f49a304 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@xxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 arch/arm/kernel/smp.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 57db122..26cdc49 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -443,9 +443,7 @@ 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
@@ -548,7 +546,9 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
 
 	switch (ipinr) {
 	case IPI_TIMER:
+		irq_enter();
 		ipi_timer();
+		irq_exit();
 		break;
 
 	case IPI_RESCHEDULE:
@@ -556,15 +556,21 @@ 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:


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