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

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Date:	Mon, 1 Nov 2010 17:16:39 +0100
From:	Michał Mirosław <mirqus@...il.com>
To:	Dmitry Artamonow <mad_soft@...ox.ru>
Cc:	linux-usb@...r.kernel.org,
	David Brownell <dbrownell@...rs.sourceforge.net>,
	Greg Kroah-Hartman <gregkh@...e.de>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Tom Herbert <therbert@...gle.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] USB: gadget: fix ethernet gadget crash in gether_setup

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?

Best Regards,
Michał Mirosław
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