[tip:irq/urgent] irq: Ensure irq_exit() code runs with interrupts disabled

[tip-bot for Thomas Gleixner <tipbot@zytor.com>]

Commit-ID:  630e7580f681475d92d87e78373e4136096e12f2
Gitweb:     http://git.kernel.org/tip/630e7580f681475d92d87e78373e4136096e12f2
Author:     Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Wed, 20 Feb 2013 22:00:48 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Thu, 21 Feb 2013 18:32:44 +0100

irq: Ensure irq_exit() code runs with interrupts disabled

We had already a few problems with code called from irq_exit() when
interrupted from a nesting interrupt. This can happen on architectures
which do not define __ARCH_IRQ_EXIT_IRQS_DISABLED.

__ARCH_IRQ_EXIT_IRQS_DISABLED should go away and we want to make it
mandatory to call irq_exit() with interrupts disabled.

As a temporary protection disable interrupts for those architectures
which do not define __ARCH_IRQ_EXIT_IRQS_DISABLED and add a WARN_ONCE
when an architecture which defines __ARCH_IRQ_EXIT_IRQS_DISABLED calls
irq_exit() with interrupts enabled.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linuxfoundation.org>
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1302202155320.22263@ionos

---
 kernel/softirq.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kernel/softirq.c b/kernel/softirq.c
index f5cc25f..d1f7943 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -341,6 +341,14 @@ static inline void invoke_softirq(void)
  */
 void irq_exit(void)
 {
+#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
+	unsigned long flags;
+
+	local_irq_save(flags);
+#else
+	WARN_ON_ONCE(!irqs_disabled();
+#endif
+
 	account_irq_exit_time(current);
 	trace_hardirq_exit();
 	sub_preempt_count(IRQ_EXIT_OFFSET);
@@ -354,6 +362,9 @@ void irq_exit(void)
 #endif
 	rcu_irq_exit();
 	sched_preempt_enable_no_resched();
+#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
+	local_irq_restore(flags);
+#endif
 }
 
 /*