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

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Date:	Wed, 16 May 2007 17:26:38 +0530
From:	"Satyam Sharma" <satyam.sharma@...il.com>
To:	"Marcel Holtmann" <marcel@...tmann.org>
Cc:	"Jiri Kosina" <jikos@...os.cz>, "Greg KH" <gregkh@...e.de>,
	"Jeremy Fitzhardinge" <jeremy@...p.org>, maxk@...lcomm.com,
	bluez-devel@...ts.sourceforge.net,
	"Cedric Le Goater" <clg@...ibm.com>,
	"Linux Kernel Mailing List" <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

Hi Marcel,

On 5/16/07, Marcel Holtmann <marcel@...tmann.org> wrote:
> Hi Satayam,
>
> > > > (later)
> > > > I Googled a bit to see if this problem was faced elsewhere in the kernel
> > > > too. Saw the following commit by Ingo Molnar
> > > > (9883a13c72dbf8c518814b6091019643cdb34429):
> > > > -     lock_sock(sock->sk);
> > > > +     local_bh_disable();
> > > > +     bh_lock_sock_nested(sock->sk);
> > > >       rc = selinux_netlbl_socket_setsid(sock, sksec->sid);
> > > > -     release_sock(sock->sk);
> > > > +     bh_unlock_sock(sock->sk);
> > > > +     local_bh_enable();
> > > > Is it _really_ *this* simple?
> > > [...]
> > > actually this *seems* to be proper solution also for our case, thanks for
> > > pointing this out. I will think about it once again, do some more tests
> > > with this locking scheme, and will let you know.
> >
> > Yes, I can almost confirm that this (open-coding of spin_lock_bh,
> > effectively) is the proper solution (Rusty's unreliable guide to
> > kernel-locking needs to be next to every developer's keyboard :-)
> > I also came across this idiom in other places in the networking code
> > so it seems to be pretty much the standard way. I wish I owned
> > bluetooth hardware, could've tested this for you myself.
>
> does this mean we should revert previous changes to the locking or only
> apply this on top of it?

I've fixed a simple patch on top of 2.6.22-rc1 below.

Signed-off-by: Satyam Sharma <ssatyam@....iitk.ac.in>

diff -ruNp a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
--- a/net/bluetooth/hci_sock.c	2007-05-16 17:31:06.000000000 +0530
+++ b/net/bluetooth/hci_sock.c	2007-05-16 17:33:36.000000000 +0530
@@ -665,7 +665,8 @@ static int hci_sock_dev_event(struct not
 		/* Detach sockets from device */
 		read_lock(&hci_sk_list.lock);
 		sk_for_each(sk, node, &hci_sk_list.head) {
-			lock_sock(sk);
+			local_bh_disable();
+			bh_lock_sock_nested(sk);
 			if (hci_pi(sk)->hdev == hdev) {
 				hci_pi(sk)->hdev = NULL;
 				sk->sk_err = EPIPE;
@@ -674,6 +675,8 @@ static int hci_sock_dev_event(struct not

 				hci_dev_put(hdev);
 			}
+			bh_unlock_sock(sk);
+			local_bh_enable();
 			release_sock(sk);
 		}
 		read_unlock(&hci_sk_list.lock);
-
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