From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 31 Jan 2012 09:59:31 +0200 From: Emeltchenko Andrei To: Ulisses Furquim Cc: linux-bluetooth@vger.kernel.org Subject: Re: [RFCv0 1/5] Bluetooth: Use locks in RCU updater code Message-ID: <20120131075928.GA15048@aemeltch-MOBL1> References: <1327936146-13897-1-git-send-email-Andrei.Emeltchenko.news@gmail.com> <1327936146-13897-2-git-send-email-Andrei.Emeltchenko.news@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 In-Reply-To: Sender: linux-bluetooth-owner@vger.kernel.org List-ID: Hi Ulisses, On Mon, Jan 30, 2012 at 03:17:15PM -0200, Ulisses Furquim wrote: > 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? I am adding lock to updaters and to the places we need to sleep and rcu_read_lock cannot be used. This patch adds locks to updaters and following patches cover other places. Maybe I need to split them better. Best regards Andrei Emeltchenko