netdev - Re: [PATCH] USB: gadget: fix ethernet gadget crash in gether

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Message-Id: <20101101.092246.104046133.davem@davemloft.net>
Date:	Mon, 01 Nov 2010 09:22:46 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	mirqus@...il.com
Cc:	mad_soft@...ox.ru, linux-usb@...r.kernel.org,
	dbrownell@...rs.sourceforge.net, gregkh@...e.de,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	therbert@...gle.com
Subject: Re: [PATCH] USB: gadget: fix ethernet gadget crash in gether_setup

From: Michał Mirosław <mirqus@...il.com>
Date: Mon, 1 Nov 2010 17:16:39 +0100

> 2010/10/28 Dmitry Artamonow <mad_soft@...ox.ru>:
>> Crash is triggered by commit e6484930d7 ("net: allocate tx queues in
>> register_netdevice"), which moved tx netqueue creation into register_netdev.
>> So now calling netif_stop_queue() before register_netdev causes an oops.
>> Move netif_stop_queue() after net device registration to fix crash.
>>
>> Signed-off-by: Dmitry Artamonow <mad_soft@...ox.ru>
>> ---
>>  drivers/usb/gadget/u_ether.c |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/usb/gadget/u_ether.c b/drivers/usb/gadget/u_ether.c
>> index 6bb876d..cb23355 100644
>> --- a/drivers/usb/gadget/u_ether.c
>> +++ b/drivers/usb/gadget/u_ether.c
>> @@ -797,7 +797,6 @@ int gether_setup(struct usb_gadget *g, u8 ethaddr[ETH_ALEN])
>>         *  - iff DATA transfer is active, carrier is "on"
>>         *  - tx queueing enabled if open *and* carrier is "on"
>>         */
>> -       netif_stop_queue(net);
>>        netif_carrier_off(net);
>>
>>        dev->gadget = g;
>> @@ -812,6 +811,7 @@ int gether_setup(struct usb_gadget *g, u8 ethaddr[ETH_ALEN])
>>                INFO(dev, "MAC %pM\n", net->dev_addr);
>>                INFO(dev, "HOST MAC %pM\n", dev->host_mac);
>>
>> +               netif_stop_queue(net);
>>                the_dev = dev;
>>        }
>>
> 
> What about a race between register_netdev() -> open() -> rest of
> gether_setup() ? What is this netif_stop_queue() here needed for?

Nothing, it should be completely removed.