[GIT pull] genirq fixes for 2.6.31

[Thomas Gleixner <tglx@linutronix.de>]

Linus,

Please pull the latest irq-fixes-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git irq-fixes-for-linus

Thanks,

	tglx

------------------>
Thomas Gleixner (1):
      genirq: Prevent race between free_irq() and handle_IRQ_event()


 kernel/irq/handle.c |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
index 065205b..4e7f17a 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -403,8 +403,16 @@ irqreturn_t handle_IRQ_event(unsigned int irq, struct irqaction *action)
 			 */
 			if (likely(!test_bit(IRQTF_DIED,
 					     &action->thread_flags))) {
+				struct task_struct *tsk = action->thread;
+
 				set_bit(IRQTF_RUNTHREAD, &action->thread_flags);
-				wake_up_process(action->thread);
+				/*
+				 * Check tsk as we might race against
+				 * free_irq which sets action->thread
+				 * to NULL
+				 */
+				if (tsk)
+					wake_up_process(tsk);
 			}
 
 			/* Fall through to add to randomness */