From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932656AbdBWA5B (ORCPT ); Wed, 22 Feb 2017 19:57:01 -0500 Received: from mail-pg0-f43.google.com ([74.125.83.43]:34490 "EHLO mail-pg0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932426AbdBWA4x (ORCPT ); Wed, 22 Feb 2017 19:56:53 -0500 From: John Stultz To: lkml Cc: John Stultz , Xinliang Liu , Rongrong Zou , Xinwei Kong , Chen Feng , David Airlie , Daniel Vetter , Sean Paul , dri-devel@lists.freedesktop.org Subject: [RFC][PATCH] drm: kirin: Add a mutex to avoid fb initialization race Date: Wed, 22 Feb 2017 16:56:23 -0800 Message-Id: <1487811383-6915-1-git-send-email-john.stultz@linaro.org> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In some cases I've been seeing a race where two framebuffers would be initialized, as kirin_fbdev_output_poll_changed() might get called quickly in succession, resulting in the fb initialization happening twice. This could cause the system to boot up with a blank screen. This patch adds a simple mutex to serialize it and seems to avoid the race. Obviously I suspect this patch isn't the best solution, but I wanted to send it out as something concrete to discuss the bug. Suggestions or feedback for a better solution would be greatly appreciated. Cc: Xinliang Liu Cc: Rongrong Zou Cc: Xinwei Kong Cc: Chen Feng Cc: David Airlie Cc: Daniel Vetter Cc: Sean Paul Cc: dri-devel@lists.freedesktop.org Signed-off-by: John Stultz --- drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.c b/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.c index ebd5f4f..80c607f 100644 --- a/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.c +++ b/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.c @@ -50,11 +50,13 @@ static int kirin_drm_kms_cleanup(struct drm_device *dev) return 0; } +static DEFINE_MUTEX(fb_lock); #ifdef CONFIG_DRM_FBDEV_EMULATION static void kirin_fbdev_output_poll_changed(struct drm_device *dev) { struct kirin_drm_private *priv = dev->dev_private; + mutex_lock(&fb_lock); if (priv->fbdev) { drm_fbdev_cma_hotplug_event(priv->fbdev); } else { @@ -64,6 +66,7 @@ static void kirin_fbdev_output_poll_changed(struct drm_device *dev) if (IS_ERR(priv->fbdev)) priv->fbdev = NULL; } + mutex_unlock(&fb_lock); } #endif -- 2.7.4