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* Re: [BISECTED] 5.12 hangs at reboot
       [not found] <CAHk-=wjjBEkOdj=C2HxjFu0zaKT46Yw52t7PyCCYFRaFdu57Sw@mail.gmail.com>
@ 2021-04-27  7:43 ` Herbert Xu
  0 siblings, 0 replies; only message in thread
From: Herbert Xu @ 2021-04-27  7:43 UTC (permalink / raw)
  To: Linus Torvalds; +Cc: harald, johannes, linux-kernel, netdev

Linus Torvalds <torvalds@linux-foundation.org> wrote:
>
> At a guess, there is some other sequence that takes the rtnl lock, and
> then takes the wiphy_lock inside of it, and we have a ABBA deadlock.

The most common cause of these lockups is a stray reference on
some kind of a network object, e.g., a socket or some such.  This
then causes the underlying network device to be reference counted
and triggers a lock-up if that network device needs to be removed.

> I _hate_ that stupid rtnl lock. It's come up before. Several times.
> It's probably the most broken lock in the kernel.

Yes, it's the networking equivalent of the BKL.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

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2021-04-27  7:43 ` [BISECTED] 5.12 hangs at reboot Herbert Xu

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