From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751754AbdBYBpo (ORCPT ); Fri, 24 Feb 2017 20:45:44 -0500 Received: from szxga01-in.huawei.com ([45.249.212.187]:2848 "EHLO dggrg01-dlp.huawei.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751593AbdBYBpm (ORCPT ); Fri, 24 Feb 2017 20:45:42 -0500 Subject: Re: [RFC][PATCH v2] drm: kirin: Add a mutex to avoid fb initialization race To: John Stultz , lkml References: <1487985916-29450-1-git-send-email-john.stultz@linaro.org> <58B0E044.6010905@hisilicon.com> CC: Rongrong Zou , Xinwei Kong , Chen Feng , "David Airlie" , Daniel Vetter , Sean Paul , From: liuxinliang Message-ID: <58B0E1C9.7020807@hisilicon.com> Date: Sat, 25 Feb 2017 09:45:45 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 MIME-Version: 1.0 In-Reply-To: <58B0E044.6010905@hisilicon.com> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.46.44.48] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A090206.58B0E1BF.0056,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2014-11-16 11:51:01, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: b4aa924d10399fef433395166b932f5b Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2017/2/25 9:39, liuxinliang wrote: > Hi John, > > The patch seems good to me, except one minus comment. > Maybe change fb_lock to fbdev_lock would be better. > > Thanks, > -xinliang > > On 2017/2/25 9:25, John Stultz wrote: >> 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 >> 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. >> >> Suggestions or feedback 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 | 4 ++++ >> drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.h | 1 + >> 2 files changed, 5 insertions(+) >> >> diff --git a/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.c >> b/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.c >> index 7ec93ae..b83556a 100644 >> --- a/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.c >> +++ b/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.c >> @@ -55,6 +55,7 @@ static void kirin_fbdev_output_poll_changed(struct >> drm_device *dev) >> { >> struct kirin_drm_private *priv = dev->dev_private; >> + mutex_lock(&priv->fb_lock); >> if (priv->fbdev) { >> drm_fbdev_cma_hotplug_event(priv->fbdev); >> } else { >> @@ -63,6 +64,7 @@ static void kirin_fbdev_output_poll_changed(struct >> drm_device *dev) >> if (IS_ERR(priv->fbdev)) >> priv->fbdev = NULL; >> } >> + mutex_unlock(&priv->fb_lock); >> } >> #endif >> @@ -95,6 +97,8 @@ static int kirin_drm_kms_init(struct drm_device >> *dev) >> if (!priv) >> return -ENOMEM; >> + mutex_init(&priv->fb_lock); And put this line in CONFIG_DRM_FBDEV_EMULATION >> + >> dev->dev_private = priv; >> dev_set_drvdata(dev->dev, dev); >> diff --git a/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.h >> b/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.h >> index 7f60c649..9b6d2b1 100644 >> --- a/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.h >> +++ b/drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.h >> @@ -23,6 +23,7 @@ struct kirin_drm_private { >> #ifdef CONFIG_DRM_FBDEV_EMULATION >> struct drm_fbdev_cma *fbdev; >> #endif >> + struct mutex fb_lock; And here. -xinliang >> }; >> extern const struct kirin_dc_ops ade_dc_ops; >