Re: [PATCH 1/5] fbdev: Hot-unplug firmware fb devices on forced removal

[Javier Martinez Canillas <javierm@redhat.com>]

On 1/24/22 14:52, Javier Martinez Canillas wrote:

[snip]

>> @@ -1898,9 +1917,13 @@ EXPORT_SYMBOL(register_framebuffer);
>>  void
>>  unregister_framebuffer(struct fb_info *fb_info)
>>  {
>> -	mutex_lock(&registration_lock);
>> +	bool forced_out = fb_info->forced_out;
>> +
>> +	if (!forced_out)
>> +		mutex_lock(&registration_lock);
>>  	do_unregister_framebuffer(fb_info);
>> -	mutex_unlock(&registration_lock);
>> +	if (!forced_out)
>> +		mutex_unlock(&registration_lock);
>>  }
> 
> I'm not sure to follow the logic here. The forced_out bool is set when the
> platform device is unregistered in do_remove_conflicting_framebuffers(),
> but shouldn't the struct platform_driver .remove callback be executed even
> in this case ?
> 
> That is, the platform_device_unregister() will trigger the call to the
> .remove callback that in turn will call unregister_framebuffer().
> 
> Shouldn't we always hold the mutex when calling do_unregister_framebuffer() ?
> 

Scratch that, I got it now. That's exactly the reason why you skip the
mutext_lock(). After adding the check for dev, feel free to add:

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>

Best regards,
-- 
Javier Martinez Canillas
Linux Engineering
Red Hat