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

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Message-ID: <CANEJEGu3j4a6LOiyD-Qbs5nX4wc4spWQB3ZukmEa1J6VPUg+=g@mail.gmail.com>
Date:	Thu, 20 Mar 2014 09:35:23 -0700
From:	Grant Grundler <grundler@...gle.com>
To:	Oliver Neukum <oneukum@...e.de>
Cc:	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>,
	Julius Werner <jwerner@...omium.org>
Subject: Re: usbnet: driver_info->stop required to stop USB interrupts?

On Thu, Mar 20, 2014 at 12:15 AM, Oliver Neukum <oneukum@...e.de> wrote:
...
> I have an idea. Could you test this patch?
...
> -       if (dev->wait) {
..
> +       if (waitqueue_active(&dev->wait)) {

Yes - building new image now (and transfer to USB and boot from USB).
Should know in an hour or so (doing other things in parallel).

I was sure the problem is in usbnet_bh() since that's the only code
change I'm actually exercising (so far). The way I was reading the
code, we might see extra wake_up calls...but there is clearly more
going on.

Can you please explain why we need to check if the waitqueue is active?

This patch should also add a comment to hint why waitqueue_active()
must be called.
Why? Several experienced people looked at the code and didn't see the
problem including the original author of the patch.

thanks,
grant
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