Return-Path: MIME-Version: 1.0 In-Reply-To: <1327936146-13897-2-git-send-email-Andrei.Emeltchenko.news@gmail.com> References: <1327936146-13897-1-git-send-email-Andrei.Emeltchenko.news@gmail.com> <1327936146-13897-2-git-send-email-Andrei.Emeltchenko.news@gmail.com> Date: Mon, 30 Jan 2012 15:17:15 -0200 Message-ID: Subject: Re: [RFCv0 1/5] Bluetooth: Use locks in RCU updater code From: Ulisses Furquim To: Emeltchenko Andrei Cc: linux-bluetooth@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-bluetooth-owner@vger.kernel.org List-ID: Hi Andrei, On Mon, Jan 30, 2012 at 1:09 PM, Emeltchenko Andrei wrote: > From: Andrei Emeltchenko > > Code which makes changes to RCU list shall be locked. > > Signed-off-by: Andrei Emeltchenko > --- > ?net/bluetooth/l2cap_core.c | ? 13 +++++++++---- > ?1 files changed, 9 insertions(+), 4 deletions(-) > > diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c > index 6991821..f54768e 100644 > --- a/net/bluetooth/l2cap_core.c > +++ b/net/bluetooth/l2cap_core.c > @@ -743,13 +743,13 @@ static void l2cap_send_disconn_req(struct l2cap_conn *conn, struct l2cap_chan *c > ?/* ---- L2CAP connections ---- */ > ?static void l2cap_conn_start(struct l2cap_conn *conn) > ?{ > - ? ? ? struct l2cap_chan *chan; > + ? ? ? struct l2cap_chan *chan, *tmp; > > ? ? ? ?BT_DBG("conn %p", conn); > > - ? ? ? rcu_read_lock(); > + ? ? ? mutex_lock(&conn->chan_lock); > > - ? ? ? list_for_each_entry_rcu(chan, &conn->chan_l, list) { > + ? ? ? list_for_each_entry_safe(chan, tmp, &conn->chan_l, list) { > ? ? ? ? ? ? ? ?struct sock *sk = chan->sk; > > ? ? ? ? ? ? ? ?bh_lock_sock(sk); > @@ -829,7 +829,7 @@ static void l2cap_conn_start(struct l2cap_conn *conn) > ? ? ? ? ? ? ? ?bh_unlock_sock(sk); > ? ? ? ?} > > - ? ? ? rcu_read_unlock(); > + ? ? ? mutex_unlock(&conn->chan_lock); > ?} > > ?/* Find socket with cid and source bdaddr. > @@ -1009,6 +1009,8 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err) > > ? ? ? ?kfree_skb(conn->rx_skb); > > + ? ? ? mutex_lock(&conn->chan_lock); > + > ? ? ? ?/* Kill channels */ > ? ? ? ?list_for_each_entry_safe(chan, l, &conn->chan_l, list) { > ? ? ? ? ? ? ? ?sk = chan->sk; > @@ -1018,6 +1020,8 @@ static void l2cap_conn_del(struct hci_conn *hcon, int err) > ? ? ? ? ? ? ? ?chan->ops->close(chan->data); > ? ? ? ?} > > + ? ? ? mutex_unlock(&conn->chan_lock); > + > ? ? ? ?hci_chan_del(conn->hchan); > > ? ? ? ?if (conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_SENT) > @@ -1075,6 +1079,7 @@ static struct l2cap_conn *l2cap_conn_add(struct hci_conn *hcon, u8 status) > ? ? ? ?conn->feat_mask = 0; > > ? ? ? ?spin_lock_init(&conn->lock); > + ? ? ? mutex_init(&conn->chan_lock); > > ? ? ? ?INIT_LIST_HEAD(&conn->chan_l); > I was under the impression you'd remove RCU for conn->chan_l completely. You're adding a lock only in the updaters? If so, please take a look at commit 3d57dc680 which shows all changes from mutex to RCU. I don't think just adding a lock/unlock in l2cap_conn_start and l2cap_conn_del will be enough. l2cap_chan_add seems to be called from other contexts and it does a list_add_rcu(). Have you thought of that? Regards, -- Ulisses Furquim ProFUSION embedded systems http://profusion.mobi Mobile: +55 19 9250 0942 Skype: ulissesffs