commit 07d5435afb2bbf4bcdb1cffd47815fcc5678eeec
Author: Pierre Willenbrock <pierre@pirsoft.de>
Date:   Fri Nov 28 23:23:21 2008 +0100

    Make irq storm go away.

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index c367358..3e398f9 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -212,10 +212,11 @@ irqreturn_t i915_driver_irq_handler(DRM_IRQ_ARGS)
 			I915_WRITE(PIPEBSTAT, pipeb_stats);
 			irq_received = 1;
 		}
-		spin_unlock_irqrestore(&dev_priv->user_irq_lock, irqflags);
 
-		if (!irq_received)
+		if (!irq_received) {
+			spin_unlock_irqrestore(&dev_priv->user_irq_lock, irqflags);
 			break;
+		}
 
 		ret = IRQ_HANDLED;
 
@@ -231,6 +232,8 @@ irqreturn_t i915_driver_irq_handler(DRM_IRQ_ARGS)
 			DRM_WAKEUP(&dev_priv->irq_queue);
 		}
 
+		spin_unlock_irqrestore(&dev_priv->user_irq_lock, irqflags);
+
 		if (pipea_stats & vblank_status) {
 			vblank++;
 			drm_handle_vblank(dev, 0);