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Message-ID: <a847f3e65eaccf529a0e8b20a1284d73a671dae9.camel@sipsolutions.net>
Subject: Re: [BISECTED] 5.12 hangs at reboot
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Harald Arnesen <harald@skogtun.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Date:   Mon, 26 Apr 2021 22:26:47 +0200
In-Reply-To: <28e21004-13ff-9d5f-0c5d-4c1e79cf628a@skogtun.org>
References: <09464e67-f3de-ac09-28a3-e27b7914ee7d@skogtun.org>
         <CAHk-=wgA1Ma6e5qZO1EP9oMveLPJFbj=SC1R0ZewCmC-u0_r=A@mail.gmail.com>
         <28e21004-13ff-9d5f-0c5d-4c1e79cf628a@skogtun.org>
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On Mon, 2021-04-26 at 22:10 +0200, Harald Arnesen wrote:
> Linus Torvalds [26.04.2021 20:59]:
> 
> > There's a lockdep assertion there, but you don't seem to have lockdep
> > enabled. So it be interesting to see what happens if you
> > 
> >  (a) enable lockdep
> 
> At the risk of sounding stupid: where is this config option?

CONFIG_PROVE_LOCKING

I have no idea *where* it is either (in menuconfig or so), so if you're
in menuconfig, just hit / and enter PROVE_LOCKING. It'll come up with a
list of entries (probably only one) labeled (1), (2), ... Hit the number
key with the right number and menuconfig will take you there.

If you can't enable it, then you need DEBUG_KERNEL first.

But if you can e.g. switch to a VT (ctrl-alt-fn) and get a stackdump
shown on the screen while it hangs while shutting down (need to wait 2-3
minutes I guess), that's probably enough.

johannes