drm/msm: use mutex_lock_interruptible for submit ioctl

Be kinder to things that do lots of signal handling (ie. Xorg)
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/msm_gem_submit.c

@@ -372,11 +372,15 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
 	if (args->nr_cmds > MAX_CMDS)
 		return -EINVAL;
 
-	submit = submit_create(dev, gpu, args->nr_bos);
-	if (!submit)
-		return -ENOMEM;
+	ret = mutex_lock_interruptible(&dev->struct_mutex);
+	if (ret)
+		return ret;
 
-	mutex_lock(&dev->struct_mutex);
+	submit = submit_create(dev, gpu, args->nr_bos);
+	if (!submit) {
+		ret = -ENOMEM;
+		goto out_unlock;
+	}
 
 	ret = submit_lookup_objects(submit, args, file);
 	if (ret)
@@ -462,6 +466,7 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
 	submit_cleanup(submit);
 	if (ret)
 		msm_gem_submit_free(submit);
+out_unlock:
 	mutex_unlock(&dev->struct_mutex);
 	return ret;
 }