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

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Date:   Thu, 21 Sep 2017 20:22:45 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     Christian Lamparter <chunkeey@...glemail.com>,
        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, Sep 20, 2017 at 9:55 PM, Johannes Berg
<johannes@...solutions.net> wrote:
> 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().

Since I'm able to reproduce this, please let me know if you need me to
collect some debug traces to help with the triage.

Thanks!

>
> johannes
>
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