linux-kernel - Re: usb_wwan_write() called while device still being resumed

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Message-ID: <87ehgivlmg.fsf@nemi.mork.no>
Date:	Thu, 14 Feb 2013 18:41:27 +0100
From:	Bjørn Mork <bjorn@...k.no>
To:	Alex Courbot <acourbot@...dia.com>
Cc:	USB list <linux-usb@...r.kernel.org>,
	"linux-pm\@vger.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	Alexandre Courbot <gnurou@...il.com>
Subject: Re: usb_wwan_write() called while device still being resumed

Alex Courbot <acourbot@...dia.com> 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@...k.no>
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@...dia.com>
Signed-off-by: Bjørn Mork <bjorn@...k.no>
---
 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);
 			break;
+		}
 
 		/* send the data */
 		memcpy(this_urb->transfer_buffer, buf, todo);
-- 
1.7.10.4

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