[ARM] traps: don't call undef hook functions with spinlock held

Calling the undefined instruction handler functions with a
spinlock held is a recipe for must_sleep() warnings.  Avoid it.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/traps.c

@@ -288,14 +288,28 @@ void unregister_undef_hook(struct undef_hook *hook)
 	spin_unlock_irqrestore(&undef_lock, flags);
 }
 
+static int call_undef_hook(struct pt_regs *regs, unsigned int instr)
+{
+	struct undef_hook *hook;
+	unsigned long flags;
+	int (*fn)(struct pt_regs *regs, unsigned int instr) = NULL;
+
+	spin_lock_irqsave(&undef_lock, flags);
+	list_for_each_entry(hook, &undef_hook, node)
+		if ((instr & hook->instr_mask) == hook->instr_val &&
+		    (regs->ARM_cpsr & hook->cpsr_mask) == hook->cpsr_val)
+			fn = hook->fn;
+	spin_unlock_irqrestore(&undef_lock, flags);
+
+	return fn ? fn(regs, instr) : 1;
+}
+
 asmlinkage void __exception do_undefinstr(struct pt_regs *regs)
 {
 	unsigned int correction = thumb_mode(regs) ? 2 : 4;
 	unsigned int instr;
-	struct undef_hook *hook;
 	siginfo_t info;
 	void __user *pc;
-	unsigned long flags;
 
 	/*
 	 * According to the ARM ARM, PC is 2 or 4 bytes ahead,
@@ -325,17 +339,8 @@ asmlinkage void __exception do_undefinstr(struct pt_regs *regs)
 	}
 #endif
 
-	spin_lock_irqsave(&undef_lock, flags);
-	list_for_each_entry(hook, &undef_hook, node) {
-		if ((instr & hook->instr_mask) == hook->instr_val &&
-		    (regs->ARM_cpsr & hook->cpsr_mask) == hook->cpsr_val) {
-			if (hook->fn(regs, instr) == 0) {
-				spin_unlock_irqrestore(&undef_lock, flags);
+	if (call_undef_hook(regs, instr) == 0)
 		return;
-			}
-		}
-	}
-	spin_unlock_irqrestore(&undef_lock, flags);
 
 #ifdef CONFIG_DEBUG_USER
 	if (user_debug & UDBG_UNDEFINED) {