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

From: Marcel Holtmann <[email-masked]>
Date: Wed, 16 May 2007 14:16:15 +0200

Hi Satyam,

> > > > > > (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.
> 
> Eek, please ignore previous one. This one's correct.
> 
> Signed-off-by: Satyam Sharma <[email-masked]>
> 
> 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 17:38:35.000000000 +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;
> @@ -674,7 +675,8 @@ static int hci_sock_dev_event(struct not
> 
>  				hci_dev_put(hdev);
>  			}
> -			release_sock(sk);
> +			bh_unlock_sock(sk);
> +			local_bh_enable();
>  		}
>  		read_unlock(&hci_sk_list.lock);
>  	}

since Jiri has a good test case for it, I leave it to him for testing.
If he confirms that this fixes the locking issues, then this is

Signed-off-by: Marcel Holtmann <[email-masked]>

Regards

Marcel

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