Re: [RFC][PATCH v2] drm: kirin: Add a mutex to avoid fb initialization race

From: liuxinliang
Date: Fri Feb 24 2017 - 20:45:47 EST




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 <z.liuxinliang@xxxxxxxxxxxxx>
Cc: Rongrong Zou <zourongrong@xxxxxxxxx>
Cc: Xinwei Kong <kong.kongxinwei@xxxxxxxxxxxxx>
Cc: Chen Feng <puck.chen@xxxxxxxxxxxxx>
Cc: David Airlie <airlied@xxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Sean Paul <seanpaul@xxxxxxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
---
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;