Re: bug: deadlock in rtl8192cu

["Patrik, Kluba" <pkluba@dension.com>]

On Wed, 13 Mar 2013 15:25:05 +0100
"Patrik, Kluba" <pkluba@dension.com> wrote:

> According to http://lwn.net/Articles/37889/ no sleeping functions
> should be called inside an rcu_read_lock() region. No sleeping can
> not be guaranteed for USB transfers.

To correct myself: for synchronous USB transfers. usb_submit_urb() and
friends are safe. Rewriting things in rtlwifi to do async transfers is
a tremendous job, and might not help at all as the termination of the
callback has still be waited under RCU. 

But how about something like this?


rcu_read_lock();
sta = ...
increase_reference_count();
rcu_read_unlock();

... do all the might-sleeping things here ...

decrease_reference_count_and_call_callback_if_necessary();



I have found an example for rcu_read_lock() + kref_get() here:
https://lists.open-mesh.org/pipermail/b.a.t.m.a.n/2011-February/004234.html

Regards,
Patrik

-- 
Patrik KLUBA
Software Developer at

DENSION Audio Systems Ltd.
H-1116 Budapest, Sztregova u. 1
Phone: +36 1 463 0470
Fax:   +36 1 463 0479
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