linux-kernel - Re: scheduling while atomic: br2684ctl (atm)

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Message-ID: <20100922144329.0cb3cf86@thirdoffive.cmf.nrl.navy.mil>
Date:	Wed, 22 Sep 2010 14:43:29 -0400
From:	chas williams - CONTRACTOR <chas@....nrl.navy.mil>
To:	Mikko Vinni <mmvinni@...oo.com>
Cc:	Karl Hiramoto <karl@...amoto.org>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: scheduling while atomic: br2684ctl (atm)

On Wed, 22 Sep 2010 00:42:29 -0700 (PDT)
Mikko Vinni <mmvinni@...oo.com> wrote:

> I get the following message apparently every time (on 2.6.36-rc4+ at
> least) when killing any old br2684ctl processes.
> "unregister_atmdevice_notifier" was added by
> 7313bb8f ("atm: propagate signal changes via notifier") so perhaps
> the unregister
> part was not tested properly for rcu interaction?

it looks like atomic_notifier_chain_unregister() cannot be called in an
atomic context.  the only reason there is a lock is to the list of
br2684_devs atomically.  however, i think the event handler could be
made to just register/unregister on module load/unload instead.

> So far I haven't noticed any ill effects from the message. Let me
> know if I should test something. Thanks.

it isnt good.  it should be fixed.  unless someone has a better idea i
will go ahead with the above.

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