linux-kernel - [ 04/68] ARM: fix rcu stalls on SMP platforms

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Date:	Thu, 12 Jul 2012 16:01:38 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk,
	Russell King <rmk+kernel@....linux.org.uk>,
	UCHINO Satoshi <satoshi.uchino@...hiba.co.jp>
Subject: [ 04/68] ARM: fix rcu stalls on SMP platforms

From: Greg KH <gregkh@...uxfoundation.org>

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

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

From: Russell King <rmk+kernel@....linux.org.uk>

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@....linux.org.uk>
[add irq_enter()/irq_exit() in do_local_timer]
Signed-off-by: UCHINO Satoshi <satoshi.uchino@...hiba.co.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm/kernel/smp.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -445,9 +445,7 @@ static DEFINE_PER_CPU(struct clock_event
 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_LOCAL_TIMERS
@@ -458,7 +456,9 @@ asmlinkage void __exception_irq_entry do
 
 	if (local_timer_ack()) {
 		__inc_irq_stat(cpu, local_timer_irqs);
+		irq_enter();
 		ipi_timer();
+		irq_exit();
 	}
 
 	set_irq_regs(old_regs);
@@ -568,7 +568,9 @@ asmlinkage void __exception_irq_entry do
 
 	switch (ipinr) {
 	case IPI_TIMER:
+		irq_enter();
 		ipi_timer();
+		irq_exit();
 		break;
 
 	case IPI_RESCHEDULE:
@@ -576,15 +578,21 @@ asmlinkage void __exception_irq_entry do
 		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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