netdev - Re: 2.6.21-rc7: BUG: sleeping function called from invalid context at net/core/sock.c:1523

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Message-ID: <Pine.LNX.4.64.0704240954200.20657@twin.jikos.cz>
Date:	Tue, 24 Apr 2007 09:59:38 +0200 (CEST)
From:	Jiri Kosina <jikos@...os.cz>
To:	Herbert Xu <herbert@...dor.apana.org.au>
cc:	jeremy@...p.org, Greg KH <gregkh@...e.de>,
	Marcel Holtmann <marcel@...tmann.org>, maxk@...lcomm.com,
	bluez-devel@...ts.sourceforge.net, clg@...ibm.com,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: 2.6.21-rc7: BUG: sleeping function called from invalid context
 at net/core/sock.c:1523

On Tue, 24 Apr 2007, Herbert Xu wrote:

> > Hmm, *sigh*. I guess the patch below fixes the problem, but it is a 
> > masterpiece in the field of ugliness. And I am not sure whether it is 
> > completely correct either. Are there any immediate ideas for better 
> > solution with respect to how struct sock locking works?
> Please cc such patches to netdev.  Thanks.

Hi Herbert,

well it's pretty much bluetooth-specific, and bluez-devel was CCed, but 
OK.

> > diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
> > index 71f5cfb..c5c93cd 100644
> > --- a/net/bluetooth/hci_sock.c
> > +++ b/net/bluetooth/hci_sock.c
> > @@ -656,7 +656,10 @@ static int hci_sock_dev_event(struct notifier_block *this, unsigned long event,
> >                /* Detach sockets from device */
> >                read_lock(&hci_sk_list.lock);
> >                sk_for_each(sk, node, &hci_sk_list.head) {
> > -                       lock_sock(sk);
> > +                       if (in_atomic())
> > +                               bh_lock_sock(sk);
> > +                       else
> > +                               lock_sock(sk);
> 
> This doesn't do what you think it does.  bh_lock_sock can still succeed
> even with lock_sock held by someone else.

I know, this was precisely the reason why I converted the bh_lock_sock() 
to lock_sock() here some time ago (as it was racy with 
l2cap_connect_cfm()).

> Does this need to occur immediately when an event occurs? If not I'd
> suggest moving this into a workqueue.

Will have to check whether this will be processed properly in time when 
going to suspend.

Thanks,

-- 
Jiri Kosina
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