Re: [PATCH v3] EM28xx - fix deadlock when unplugging and replugging a DVB adapter

[Mauro Carvalho Chehab <mchehab@redhat.com>]

Em 25-09-2011 16:28, Chris Rankin escreveu:
> --- On Sun, 25/9/11, Mauro Carvalho Chehab <mchehab@redhat.com> wrote:
>> Ok, I've applied it, but it doesn't sound a good idea to me
>> to do:
>>
>> +    mutex_unlock(&dev->lock);
>>      em28xx_init_extension(dev);
>> +    mutex_lock(&dev->lock);
>>
> 
> Yes, I suppose it's the logical equivalent of moving the em28xx_init_extension(dev) call from em28xx_init_dev(), and placing it immediately after the final mutex_unlock(&dev->lock) call in em28xx_usb_probe() instead. Which would be cleaner, quite frankly.
> 
> Which stage of the v4l2 initialisation triggers the race with udev? v4l2_device_register()? 

Yes. Just after creating a device, udev tries to access it. This bug is more sensitive on
multi-CPU machines, as udev may run on another CPU.

> 
> Cheers,
> Chris
>