disp: msm: cancel all delayed_works before triggering msm_lastclose

This patch cancels all the delayed_off_works if scheduled and flushes
the display threads for completion during msm_lastclose. The commit
from msm_lastclose client modeset to disable any crtcs if enabled is
always scheduled on primary crtc_commit thread. In the current issue,
delayed_off_work is scheduled on secondary display crtc_commit thread
and primary crtc_commit thread is scheduled to turn off active crtcs
from msm_lastclose leading to null dereference access of sde_enc's
cur_master. This race is avoided by serializing the operations in
msm_lastclose.

Change-Id: I30cc95b925c8134f0064816ebe2cfdb86a49fb36
Signed-off-by: Jayaprakash Madisetty <quic_jmadiset@quicinc.com>

msm/msm_drv.c

@@ -1040,6 +1040,25 @@ mdss_init_fail:
 	return ret;
 }
 
+void msm_atomic_flush_display_threads(struct msm_drm_private *priv)
+{
+	int i;
+
+	if (!priv) {
+		SDE_ERROR("invalid private data\n");
+		return;
+	}
+
+	for (i = 0; i < priv->num_crtcs; i++) {
+		if (priv->disp_thread[i].thread)
+			kthread_flush_worker(&priv->disp_thread[i].worker);
+		if (priv->event_thread[i].thread)
+			kthread_flush_worker(&priv->event_thread[i].worker);
+	}
+
+	kthread_flush_worker(&priv->pp_event_worker);
+}
+
 /*
  * DRM operations:
  */
@@ -1165,6 +1184,8 @@ static void msm_lastclose(struct drm_device *dev)
 		DRM_INFO("wait for crtc mask 0x%x failed, commit anyway...\n",
 				priv->pending_crtcs);
 
+	msm_atomic_flush_display_threads(priv);
+
 	if (priv->fbdev) {
 		rc = drm_fb_helper_restore_fbdev_mode_unlocked(priv->fbdev);
 		if (rc)