[PATCH] Fix ppc64 smu driver locking

The SMU driver has a small mistake in the locking of the interrupt code,
if polled access and interrupt access race, interrupt may take a lock
and return without releasing it. This fixes it. With that patch, the
driver is rock solid with my experimental thermal control (which bangs
it pretty hard) racing with real time clock and cpufreq handling.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

drivers/macintosh/smu.c

@@ -153,8 +153,10 @@ static irqreturn_t smu_db_intr(int irq, void *arg, struct pt_regs *regs)
 	spin_lock_irqsave(&smu->lock, flags);
 
 	gpio = pmac_do_feature_call(PMAC_FTR_READ_GPIO, NULL, smu->doorbell);
-	if ((gpio & 7) != 7)
+	if ((gpio & 7) != 7) {
+		spin_unlock_irqrestore(&smu->lock, flags);
 		return IRQ_HANDLED;
+	}
 
 	cmd = smu->cmd_cur;
 	smu->cmd_cur = NULL;