drm/i915: Be irqsafe inside reset

As we want to be able to call i915_reset_engine and co from a softirq or
timer context, we need to be irqsafe at all times. So we have to forgo
the simple spin_lock_irq for the full spin_lock_irqsave.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180615093137.14270-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem.c

@@ -3166,15 +3166,17 @@ i915_gem_reset_request(struct intel_engine_cs *engine,
 		 */
 		request = i915_gem_find_active_request(engine);
 		if (request) {
+			unsigned long flags;
+
 			i915_gem_context_mark_innocent(request->gem_context);
 			dma_fence_set_error(&request->fence, -EAGAIN);
 
 			/* Rewind the engine to replay the incomplete rq */
-			spin_lock_irq(&engine->timeline.lock);
+			spin_lock_irqsave(&engine->timeline.lock, flags);
 			request = list_prev_entry(request, link);
 			if (&request->link == &engine->timeline.requests)
 				request = NULL;
-			spin_unlock_irq(&engine->timeline.lock);
+			spin_unlock_irqrestore(&engine->timeline.lock, flags);
 		}
 	}