linux-kernel - Re: [PATCH 1/3] bluetooth: add write_lock_bh to __l2cap_chan

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Message-Id: <1235856798.6074.34.camel@localhost.localdomain>
Date:	Sat, 28 Feb 2009 22:33:18 +0100
From:	Marcel Holtmann <marcel@...tmann.org>
To:	"Gustavo F. Padovan" <gustavo@....ic.unicamp.br>
Cc:	linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] bluetooth: add write_lock_bh to __l2cap_chan_link

Hi Gustavo,

> fix race condition
> 
> Signed-off-by: Gustavo F. Padovan <gustavo@....ic.unicamp.br>
> ---
>  net/bluetooth/l2cap.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
> index ca4d3b4..355f375 100644
> --- a/net/bluetooth/l2cap.c
> +++ b/net/bluetooth/l2cap.c
> @@ -175,12 +175,14 @@ static inline void __l2cap_chan_link(struct l2cap_chan_list *l, struct sock *sk)
>  {
>  	sock_hold(sk);
>  
> +	write_lock_bh(&l->lock);
>  	if (l->head)
>  		l2cap_pi(l->head)->prev_c = sk;
>  
>  	l2cap_pi(sk)->next_c = l->head;
>  	l2cap_pi(sk)->prev_c = NULL;
>  	l->head = sk;
> +	write_unlock_bh(&l->lock);
>  }

a general rule of thumb is that function starting with __ are the ones
that don't use any kind of locking.

Regards

Marcel

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