netdev - Re: usb/net/p54: trying to register non-static key in p54_unregister

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Message-ID: <1505937307.3026.20.camel@sipsolutions.net>
Date:   Wed, 20 Sep 2017 21:55:07 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Christian Lamparter <chunkeey@...glemail.com>,
        Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Kalle Valo <kvalo@...eaurora.org>, linux-wireless@...r.kernel.org,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        syzkaller <syzkaller@...glegroups.com>,
        Stephen Boyd <sboyd@...eaurora.org>, Tejun Heo <tj@...nel.org>,
        Yong Zhang <yong.zhang0@...il.com>
Subject: Re: usb/net/p54: trying to register non-static key in
 p54_unregister_leds

On Wed, 2017-09-20 at 21:27 +0200, Christian Lamparter wrote:

> It seems this is caused as a result of:
>     -> lock_map_acquire(&work->lockdep_map);
> 	    lock_map_release(&work->lockdep_map);
> 
>     in flush_work() [0]

Agree.

> This was added by:
> 
> 	commit 0976dfc1d0cd80a4e9dfaf87bd8744612bde475a
> 	Author: Stephen Boyd <sboyd@...eaurora.org>
> 	Date:   Fri Apr 20 17:28:50 2012 -0700
> 
> 	workqueue: Catch more locking problems with flush_work()

Yes, but that doesn't matter.
    
> Looking at the Stephen's patch, it's clear that it was made
> with "static DECLARE_WORK(work, my_work)" in mind. However
> p54's led_work is "per-device", hence it is stored in the
> devices context p54_common, which is dynamically allocated.
> So, maybe revert Stephen's patch?

I disagree - as the lockdep warning says:

> > INFO: trying to register non-static key.
> > the code is fine but needs lockdep annotation.
> > turning off the locking correctness validator.

What it needs is to actually correctly go through initializing the work
at least once.

Without more information, I can't really say what's going on, but I
assume that something is failing and p54_unregister_leds() is getting
invoked without p54_init_leds() having been invoked, so essentially
it's trying to flush a work that was never initialized?

INIT_DELAYED_WORK() does, after all, initialize the lockdep map
properly via __INIT_WORK().

johannes