powerpc/irq: Move stack overflow check into a separate function

Makes do_IRQ() shorter and clearer.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/irq.c

@@ -301,27 +301,30 @@ static inline void handle_one_irq(unsigned int irq)
 }
 #endif
 
-void do_IRQ(struct pt_regs *regs)
+static inline void check_stack_overflow(void)
 {
-	struct pt_regs *old_regs = set_irq_regs(regs);
-	unsigned int irq;
-
-	irq_enter();
-
 #ifdef CONFIG_DEBUG_STACKOVERFLOW
-	/* Debugging check for stack overflow: is there less than 2KB free? */
-	{
 	long sp;
 
 	sp = __get_SP() & (THREAD_SIZE-1);
 
+	/* check for stack overflow: is there less than 2KB free? */
 	if (unlikely(sp < (sizeof(struct thread_info) + 2048))) {
 		printk("do_IRQ: stack overflow: %ld\n",
 			sp - sizeof(struct thread_info));
 		dump_stack();
 	}
-	}
 #endif
+}
+
+void do_IRQ(struct pt_regs *regs)
+{
+	struct pt_regs *old_regs = set_irq_regs(regs);
+	unsigned int irq;
+
+	irq_enter();
+
+	check_stack_overflow();
 
 	/*
 	 * Every platform is required to implement ppc_md.get_irq.