netdev - Re: [PATCH 1/2 v5] usbnet: allow status interrupt URB to always be active

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Date:	Thu, 11 Apr 2013 20:59:05 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Oliver Neukum <oliver@...kum.org>
Cc:	Dan Williams <dcbw@...hat.com>,
	Elina Pasheva <epasheva@...rrawireless.com>,
	Network Development <netdev@...r.kernel.org>,
	linux-usb <linux-usb@...r.kernel.org>,
	Rory Filer <rfiler@...rrawireless.com>,
	Phil Sutter <phil@....cc>
Subject: Re: [PATCH 1/2 v5] usbnet: allow status interrupt URB to always be active

On Thu, Apr 11, 2013 at 8:28 PM, Oliver Neukum <oliver@...kum.org> wrote:
> On Thursday 11 April 2013 20:11:13 Ming Lei wrote:
>> On Thu, Apr 11, 2013 at 7:14 PM, Oliver Neukum <oliver@...kum.org> wrote:
>> >
>> > Sorry, I misunderstood.
>>
>> No problem, :-)
>>
>> >
>> > Task A                                  Task B                          queue
>> >
>> > queue work
>> >                                                 request a reset
>> >                                                                                         allocate memory and block
>> >                                                 cancel the work
>> >                                                                                         shit happened
>>
>> If I understand the case correctly, the above deadlock can be avoided
>> by canceling rx/tx URBs at the end of pre_reset() or usbnet_disconnect(),
>
> No. cancel_work_sync() must wait for the work. The work will not finish.

The work will complete when memory is reclaimed, and the rx/tx path is
still working, so memory reclaim can continue and the deadlock may not
be caused, may it?


Thanks,
-- 
Ming Lei
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