Re: [PATCH 4/5] usb:Push BKL on open down into the drivers

[Jiri Kosina]

On Mon, 29 Mar 2010, Oliver Neukum wrote:

> > For hiddev, this causes a problem, as you introduced BKL into 
> > hiddev_connect() exactly because of the proper dependency -- we have the 
> > BKL there to avoid race after usb_register_dev() -- once the device node 
> > has been created, open() could happen on it.
> 
> Hi,
> 
> it seems to me you cannot deadlock with the BKL and an rwsem,
> as BKL will be dropped if a task blocks on the rwsem. 

Ah, right you are.

> This is not a nice feature of the BKL to use. Do you have an alternative 
> idea?

Not right now, without introducing additional lock into USB core or 
redesigning the hiddev node registration completely. Hmmm ...

Thanks,

-- 
Jiri Kosina
SUSE Labs, Novell Inc.
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