Re: usb_wwan_write() called while device still being resumed

From: BjÃrn Mork
Date: Thu Feb 14 2013 - 12:41:54 EST

Alex Courbot <acourbot@xxxxxxxxxx> writes:

> The board features a USB GSM modem using the usb_wwan module. Once in
> a while, when the system resumes from LP0, a NET_RX softirq will be
> triggered while the modem is still being resumed, calling
> usb_wwan_write(). This will cause usb_autopm_get_interface_async()
> inside usb_wwan_write() to fail because the runtime PM disable_depth
> is still equal to 1 since device_resume() has not completed yet. As a
> result, the modem just stops working.

I believe the usb_autopm_get_interface_async() failing is OK in this
case, but that should not cause the modem to stop working.

Wonder if this patch solves the problem? :

From: =?UTF-8?q?Bj=C3=B8rn=20Mork?= <bjorn@xxxxxxx>
Date: Thu, 14 Feb 2013 18:34:48 +0100
Subject: [PATCH] USB: usb_wwan: clear port busy state on error
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Reported-by: Alex Courbot <acourbot@xxxxxxxxxx>
Signed-off-by: BjÃrn Mork <bjorn@xxxxxxx>
drivers/usb/serial/usb_wwan.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/serial/usb_wwan.c b/drivers/usb/serial/usb_wwan.c
index 01c94aa..44e106d 100644
--- a/drivers/usb/serial/usb_wwan.c
+++ b/drivers/usb/serial/usb_wwan.c
@@ -230,8 +230,10 @@ int usb_wwan_write(struct tty_struct *tty, struct usb_serial_port *port,
usb_pipeendpoint(this_urb->pipe), i);

err = usb_autopm_get_interface_async(port->serial->interface);
- if (err < 0)
+ if (err < 0) {
+ clear_bit(i, &portdata->out_busy);
+ }

/* send the data */
memcpy(this_urb->transfer_buffer, buf, todo);

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