Re: [PATCH v7 2/2] drm: Prevent release fb after cleanup drm_mode_config

[jeffy <jeffy.chen@rock-chips.com>]

Hi Daniel,

On 04/12/2017 02:36 PM, Daniel Vetter wrote:
> On Tue, Apr 11, 2017 at 11:31:42AM +0800, Jeffy Chen wrote:
>> We are freeing all framebuffers in drm_mode_config_cleanup without
>> sync the drm_file's fbs list.
>>
>> So if someone try to unbind drm before release drm dev fd, the fbs
>> list would remain some invalid fb references. And that would cause
>> crash later in drm_fb_release.
>>
>> Add a sanity check to prevent that.
>>
>> Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
>
> This feels like duct-tape. The problem is that when we unplug a drm
> device, we don't properly clean this up. I think we should first clean up
> all the drm files (and make sure all ioctl and anything else completed),
> before we proceed further in the driver cleanup.
>
> Like I said, fixing unplug is going to be serious amounts of work, not
> sure you really want to do this just for a  pure debug use-cases.
> -Daniel
right, and it's ok to drop this 2 patches, the rests are already enough 
for the testing :)
>
>>
>> ---
>>
>> Changes in v7:
>> Update commit message.
>>
>> Changes in v6: None
>> Changes in v5: None
>> Changes in v2: None
>>
>>   drivers/gpu/drm/drm_framebuffer.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
>> index e8f9c13..03c1632 100644
>> --- a/drivers/gpu/drm/drm_framebuffer.c
>> +++ b/drivers/gpu/drm/drm_framebuffer.c
>> @@ -583,6 +583,11 @@ void drm_fb_release(struct drm_file *priv)
>>   {
>>   	struct drm_framebuffer *fb, *tfb;
>>   	struct drm_mode_rmfb_work arg;
>> +	struct drm_minor *minor = priv->minor;
>> +	struct drm_device *dev = minor->dev;
>> +
>> +	if (WARN_ON(!dev->mode_config.num_fb && !list_empty(&priv->fbs)))
>> +		return;
>>
>>   	INIT_LIST_HEAD(&arg.fbs);
>>
>> --
>> 2.1.4
>>
>>
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>