Merge branch 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/l…

…inux/kernel/git/tip/tip

Pull irq fix from Ingo Molnar:
 "Frederic's minimal fix for hardirq/softirq nesting crashes"

* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  irq: Force hardirq exit's softirq processing on its own stack

kernel/softirq.c

@@ -328,10 +328,19 @@ void irq_enter(void)
 
 static inline void invoke_softirq(void)
 {
-	if (!force_irqthreads)
-		__do_softirq();
-	else
+	if (!force_irqthreads) {
+		/*
+		 * We can safely execute softirq on the current stack if
+		 * it is the irq stack, because it should be near empty
+		 * at this stage. But we have no way to know if the arch
+		 * calls irq_exit() on the irq stack. So call softirq
+		 * in its own stack to prevent from any overrun on top
+		 * of a potentially deep task stack.
+		 */
+		do_softirq();
+	} else {
 		wakeup_softirqd();
+	}
 }
 
 static inline void tick_irq_exit(void)