netdev - Re: Hangs in r8152 connected to power management in kernels at least up v4.17-rc4

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Message-ID: <c1c775d4-60c1-e4ac-87e5-81e655b5beeb@suse.cz>
Date:   Wed, 16 May 2018 15:36:21 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     Hayes Wang <hayeswang@...ltek.com>,
        Oliver Neukum <ONeukum@...e.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: Hangs in r8152 connected to power management in kernels at least
 up v4.17-rc4

On 05/16/2018, 03:29 PM, Jiri Slaby wrote:
> On 05/16/2018, 02:07 PM, Hayes Wang wrote:
>> Oliver Neukum [mailto:oneukum@...e.com]
>>> Sent: Wednesday, May 16, 2018 6:10 PM
>> [...]
>>>> Besides, I find a similar issue as following.
>>>> https://www.spinics.net/lists/netdev/msg493512.html
>>>
>>> Well, if we have an imbalance in NAPI it should strike whereever
>>> it is used, not just in suspend(). Is there debugging for NAPI
>>> we could activate?
>>
>> No. The driver doesn't embed such debugging about it.
> 
> Despite of that, Oliver, I have a kernel with a debug patch (attached)
> at (suse-only link):
> https://build.suse.de/project/show/home:jirislaby:stable-drm
> 
>> And I don't find an imbalance between napi_disable() and napi_enable().
> 
> There is none, apparently (the warns never triggered). BUt still the
> driver sucks wrt both power mgmt and dock plug/unplug. Since I am using
> the patch (it upper-bounds the napi_disable loop count) and the udev
> rule below, I can really use the nic.

BTW the added warning to napi_disable indeed triggers:

> xzgrep -a -B 2 kernel:.*WARNING.*napi messages-20180*
> messages-20180503.xz:2018-04-27T09:57:00.048922+02:00 anemoi2 kernel: [158616.363052] ------------[ cut here ]------------
> messages-20180503.xz:2018-04-27T09:57:00.048979+02:00 anemoi2 kernel: [158616.363070] NAPI_STATE_SCHED never cleared
> messages-20180503.xz:2018-04-27T09:57:00.048988+02:00 anemoi2 kernel: [158616.363120] WARNING: CPU: 1 PID: 14365 at ../net/core/dev.c:5665 napi_disable+0x3d/0x80

And since I do 'ip l set dev ethX down' before unplugging the dock with
the NIC, I have not seen a single occurrence.

So I assume it must be a problem of making usb->disconnect without prior
ndo->close (or alike).

thanks,
-- 
js
suse labs