netdev - Re: [PATCH v2 2/7] USB: serial: handle suspend failure path correctly

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Message-ID: <20130314111010.GA15776@localhost>
Date:	Thu, 14 Mar 2013 12:10:10 +0100
From:	Johan Hovold <jhovold@...il.com>
To:	Ming Lei <ming.lei@...onical.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Kosina <jkosina@...e.cz>,
	Alan Stern <stern@...land.harvard.edu>,
	Oliver Neukum <oneukum@...e.de>, netdev@...r.kernel.org,
	linux-usb@...r.kernel.org, linux-input@...r.kernel.org,
	Johan Hovold <jhovold@...il.com>
Subject: Re: [PATCH v2 2/7] USB: serial: handle suspend failure path correctly

On Fri, Mar 08, 2013 at 12:15:19AM +0800, Ming Lei wrote:
> This patch kills traffic even though type->suspend returns
> failure inside usb_serial_suspend from system sleep context
> because USB core ignores the failiure and lets system sleep
> go ahread, so the serial URB traffic need to be killed
> in this case.
> 
> Cc: Johan Hovold <jhovold@...il.com>
> Signed-off-by: Ming Lei <ming.lei@...onical.com>
> ---
>  drivers/usb/serial/usb-serial.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
> index a19ed74..9d0b9c8 100644
> --- a/drivers/usb/serial/usb-serial.c
> +++ b/drivers/usb/serial/usb-serial.c
> @@ -1142,10 +1142,11 @@ int usb_serial_suspend(struct usb_interface *intf, pm_message_t message)
>  
>  	if (serial->type->suspend) {
>  		r = serial->type->suspend(serial, message);
> -		if (r < 0) {
> +		if (r < 0 && PMSG_IS_AUTO(message)) {
>  			serial->suspending = 0;
>  			goto err_out;
>  		}
> +		/* TODO: resume() might need to handle suspend failure */
>  	}
>  
>  	for (i = 0; i < serial->num_ports; ++i) {

Sorry for the late reply.

The usb-serial subdriver suspend callbacks do not and must not return
non-zero if !PMSG_IS_AUTO(message) so adding code to handle that case
merely obfuscates this fact.

I'd rather see this documented with a comment just as Bjørn suggested
for cdc_mbim and qmi_wwan.

Thanks,
Johan
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