netdev - Re: usbnet: driver_info->stop required to stop USB interrupts?

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Message-ID: <CANEJEGuaVPNZKFiXY9CywFuqghgiQqV_sii7TE3STCNvXLQ3pQ@mail.gmail.com>
Date:	Tue, 18 Mar 2014 13:51:52 -0700
From:	Grant Grundler <grundler@...gle.com>
To:	Oliver Neukum <oneukum@...e.de>
Cc:	Julius Werner <jwerner@...omium.org>,
	netdev <netdev@...r.kernel.org>, Freddy Xin <freddy@...x.com.tw>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	Allan Chou <allan@...x.com.tw>
Subject: Re: usbnet: driver_info->stop required to stop USB interrupts?

On Mon, Mar 17, 2014 at 2:55 PM, Oliver Neukum <oneukum@...e.de> wrote:
> I am hping for the reporter of the original bug to test it.

Oliver,
on a haswell system running ChromeOS-3.8 kernel, this patch as-is
resulted in a "Bad Spinlock Magic" error and subsequent pagefault.
I believe the sequence was:
   usbnet_open -> tasklet_schedule(dev->bh) -> usbnet_bh -> wake_up
(&dev->wait) -> panic

I tried adding the following change on top of your patch but believe
the plumbing still isn't quite correct since the USB device (eth0) is
reporting a link but no TX or RX of traffic:
 @@ -805,6 +807,9 @@ int usbnet_open (struct net_device *net)
                goto done;
        }

+       /* usbnet_bh() expects the spinlock to be initialized. */
+       init_waitqueue_head(&dev->wait);
+
        /* hard_mtu or rx_urb_size may change in reset() */
        usbnet_update_max_qlen(dev);

I suspect this hunk of your patch is now causing different problems at
init time:
@@ -1438,10 +1440,8 @@ static void usbnet_bh (unsigned long param)
        clear_bit(EVENT_RX_KILL, &dev->flags);

        // waiting for all pending urbs to complete?
-       if (dev->wait) {
-               if ((dev->txq.qlen + dev->rxq.qlen + dev->done.qlen) == 0) {
-                       wake_up (dev->wait);
-               }
+       if ((dev->txq.qlen + dev->rxq.qlen + dev->done.qlen) == 0) {
+               wake_up (&dev->wait);

        // or are we maybe short a few urbs?
        } else if (netif_running (dev->net) &&

Please advise on what you'd like me to try next.

cheers,
grant
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