Date: Mon, 15 Dec 2014 13:13:18 +0800
From: Peter Chen <peter.chen@freescale.com>
To: Robert Baldyga <r.baldyga@samsung.com>
CC: <balbi@ti.com>, <gregkh@linuxfoundation.org>, <linux-usb@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <m.szyprowski@samsung.com>,
        <k.opasiak@samsung.com>
Subject: Re: [PATCH] usb: gadget: udc-core: call udc_stop() before gadget
 unbind
Message-ID: <20141215051317.GC25410@shlinux2>
References: <1418390248-6254-1-git-send-email-r.baldyga@samsung.com>
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Sender: linux-kernel-owner@vger.kernel.org

On Fri, Dec 12, 2014 at 02:17:28PM +0100, Robert Baldyga wrote:
> As usb function drivers assumes that all usb request will be completed
> before function unbind call, we should supply such behavior. In some
> cases ep_disable() won't kill all request effectively, because some
> IN requests can be in running state. In such situation it's possible
> to have unbind function called before last request completion, which
> can cause problems.

Doesn't the function's disable/unbind should call usb_ep_dequeue to make
sure the transfer has ended?

.udc_stop may stop the controller, and .unbind may still visit hardware.

> 
> For example unbinding f_ecm function while request on 'notify' endpoint
> is not completed, ends up NULL pointer dereference in unbind() function.
> 
> usb_gadget_udc_stop() call causes completion of all requests so if it's
> called before gadget unbind there is no risk that some of requests will
> stay uncompleted.
> 
> Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
> ---
>  drivers/usb/gadget/udc/udc-core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/gadget/udc/udc-core.c b/drivers/usb/gadget/udc/udc-core.c
> index e31d574..6f0d233 100644
> --- a/drivers/usb/gadget/udc/udc-core.c
> +++ b/drivers/usb/gadget/udc/udc-core.c
> @@ -331,8 +331,8 @@ static void usb_gadget_remove_driver(struct usb_udc *udc)
>  
>  	usb_gadget_disconnect(udc->gadget);
>  	udc->driver->disconnect(udc->gadget);
> -	udc->driver->unbind(udc->gadget);
>  	usb_gadget_udc_stop(udc);
> +	udc->driver->unbind(udc->gadget);
>  
>  	udc->driver = NULL;
>  	udc->dev.driver = NULL;
> -- 
> 1.9.1
> 

-- 

Best Regards,
Peter Chen
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