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

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Date:   Sun, 24 Sep 2017 16:13:38 +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: [RESEND] Re: usb/net/p54: trying to register non-static key in
 p54_unregister_leds

On Sat, 2017-09-23 at 21:37 +0200, Christian Lamparter wrote:

> But this also begs the question: Is this really working then?
> From what I can tell, if CONFIG_LOCKDEP is not set then there's no
> BUG no WARN, no other splat or any other odd system behaviour. Does
> [cancel | flush]_[delayed_]work[_sync] really "just work" by
> *accident*, as long the delayed_work | work_struct is zeroed out? 

It looks like it does, but I'm not sure it's not more or less by
accident. Look at get_work_pool() for example, it might actually return
non-NULL in this case, and then in start_flush_work() you'll probably
fall into one of the few "already_gone" cases.

> And should it work in the future as well?

I guess it's not really guaranteed, the API doesn't state anything to
that effect. Not that I'm looking forward to a new workqueue rewrite ;)

johannes