e->base.event = &e->event.base;
        e->base.file_priv = file;
        e->base.destroy = ipp_free_event;
+       mutex_lock(&c_node->event_lock);
        list_add_tail(&e->base.link, &c_node->event_list);
+       mutex_unlock(&c_node->event_lock);
 
        return 0;
 }
        struct drm_exynos_ipp_send_event *e, *te;
        int count = 0;
 
+       mutex_lock(&c_node->event_lock);
        list_for_each_entry_safe(e, te, &c_node->event_list, base.link) {
                DRM_DEBUG_KMS("count[%d]e[0x%x]\n", count++, (int)e);
 
                        /* delete list */
                        list_del(&e->base.link);
                        kfree(e);
-                       return;
+                       goto out_unlock;
                }
        }
+
+out_unlock:
+       mutex_unlock(&c_node->event_lock);
+       return;
 }
 
 static void ipp_handle_cmd_work(struct device *dev,
                return -EINVAL;
        }
 
+       mutex_lock(&c_node->event_lock);
        if (list_empty(&c_node->event_list)) {
                DRM_DEBUG_KMS("event list is empty.\n");
-               return 0;
+               ret = 0;
+               goto err_event_unlock;
        }
 
        mutex_lock(&c_node->mem_lock);
        e = list_first_entry(&c_node->event_list,
                struct drm_exynos_ipp_send_event, base.link);
 
-       if (!e) {
-               DRM_ERROR("empty event.\n");
-               return -EINVAL;
-       }
-
        do_gettimeofday(&now);
        DRM_DEBUG_KMS("tv_sec[%ld]tv_usec[%ld]\n", now.tv_sec, now.tv_usec);
        e->event.tv_sec = now.tv_sec;
        list_move_tail(&e->base.link, &e->base.file_priv->event_list);
        wake_up_interruptible(&e->base.file_priv->event_wait);
        spin_unlock_irqrestore(&drm_dev->event_lock, flags);
+       mutex_unlock(&c_node->event_lock);
 
        DRM_DEBUG_KMS("done cmd[%d]prop_id[%d]buf_id[%d]\n",
                property->cmd, property->prop_id, tbuf_id[EXYNOS_DRM_OPS_DST]);
 
 err_mem_unlock:
        mutex_unlock(&c_node->mem_lock);
+err_event_unlock:
+       mutex_unlock(&c_node->event_lock);
        return ret;
 }
 
                goto err_completion;
        }
 
-       mutex_lock(&c_node->event_lock);
-
        ret = ipp_send_event(ippdrv, c_node, event_work->buf_id);
        if (ret) {
                DRM_ERROR("failed to send event.\n");
 err_completion:
        if (ipp_is_m2m_cmd(c_node->property.cmd))
                complete(&c_node->start_complete);
-
-       mutex_unlock(&c_node->event_lock);
 }
 
 static int ipp_subdrv_probe(struct drm_device *drm_dev, struct device *dev)