Re: [PATCH] fix usb skeleton driver

[Ming Lei]

On Wed, Jun 6, 2012 at 11:05 PM, Stefani Seibold <stefani@xxxxxxxxxxx> wrote:
>>
>> This one is not needed since we have minor_rwsem(drivers/usb/core/file.c)
>> to avoid the race.
>>
>
> The mutex is not for the minor handling, it is for the disconnect(). As

usb_deregister_dev is called by disconnect, and usb_deregister_dev
will acquire minor_rwsem, so there is no race between open and disconnect.
When skel_open is being called, the minor_rwsem has been held already,
so disconnect() will staying on acquiring minor_rwsem.

So sync_mutex is not necessary at all.

> mentioned in the previous posting, there is a race betwenn open() and
> connect().
>
> Oliver told me that a interface pointer can be already used by an other
> driver when the disconnect() was called.

If you mean dev->interface, that is protected by io_mutex already.


Thanks,
-- 
Ming Lei
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