Re: [syzbot] INFO: task hung in port100_probe

From: Alan Stern <stern@rowland.harvard.edu>
To: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Cc: syzbot <syzbot+abd2e0dafb481b621869@syzkaller.appspotmail.com>,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	syzkaller-bugs@googlegroups.com,
	Pavel Skripkin <paskripkin@gmail.com>,
	Thierry Escande <thierry.escande@collabora.com>,
	Andrey Konovalov <andreyknvl@gmail.com>
Subject: Re: [syzbot] INFO: task hung in port100_probe
Date: Fri, 23 Jul 2021 09:07:47 -0400	[thread overview]
Message-ID: <20210723130747.GB38923@rowland.harvard.edu> (raw)
In-Reply-To: <b007e1e5-6978-3b7a-8d7f-3d8f3a448436@canonical.com>

On Fri, Jul 23, 2021 at 11:05:09AM +0200, Krzysztof Kozlowski wrote:
> On 22/07/2021 16:47, Alan Stern wrote:
> > On Thu, Jul 22, 2021 at 04:20:10PM +0200, Krzysztof Kozlowski wrote:
> >> Anyone hints where the issue could be?
> > 
> > Here's what I wrote earlier: "It looks like the problem stems from the fact 
> > that port100_send_frame_async() submits two URBs, but 
> > port100_send_cmd_sync() only waits for one of them to complete.  The other 
> > URB may then still be active when the driver tries to reuse it."
> 
> I see now you replied this to earlier syzbot report about "URB submitted
> while active". Here is a slightly different issue - hung task on waiting
> for completion coming from device ack.
> 
> However maybe these are both similar or at least come from similar root
> cause in the driver.

Exactly what I was thinking.  :-)

> > Of course, there may be more than one problem, so we may not be talking 
> > about the same thing.
> > 
> > Does that help at all?
> 
> Thanks, it gives me some ideas to look into although I spent already too
> much time on this old driver. I doubt it has any users so maybe better
> to mark it as BROKEN...

Whatever you think is best.  I know nothing about port100.

Alan Stern