Hi Andrei,
On Fri, Feb 17, 2012 at 11:43 AM, Emeltchenko Andrei
<Andrei.Emeltchenko.news@xxxxxxxxx> wrote:
> From: Andrei Emeltchenko <andrei.emeltchenko@xxxxxxxxx>
>
> Usage of RCU list looks not reasonalbe for a number of reasons:
> our code sleep and we have to use socket spinlocks, some parts
> of code are updaters thus we need to use mutexes anyway.
>
> Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@xxxxxxxxx>
> ---
> net/bluetooth/l2cap_core.c | 98 ++++++++++++++++++++-----------------------
> 1 files changed, 46 insertions(+), 52 deletions(-)
>
> diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
> index 63539f9..109b62d 100644
> --- a/net/bluetooth/l2cap_core.c
> +++ b/net/bluetooth/l2cap_core.c
> @@ -77,36 +77,24 @@ static void l2cap_send_disconn_req(struct l2cap_conn *conn,
>
> static struct l2cap_chan *__l2cap_get_chan_by_dcid(struct l2cap_conn *conn, u16 cid)
> {
> - struct l2cap_chan *c, *r = NULL;
> -
> - rcu_read_lock();
> + struct l2cap_chan *c;
>
> - list_for_each_entry_rcu(c, &conn->chan_l, list) {
> - if (c->dcid == cid) {
> - r = c;
> - break;
> - }
> + list_for_each_entry(c, &conn->chan_l, list) {
> + if (c->dcid == cid)
> + return c;
> }
> -
> - rcu_read_unlock();
> - return r;
> + return NULL;
> }
>
> static struct l2cap_chan *__l2cap_get_chan_by_scid(struct l2cap_conn *conn, u16 cid)
> {
> - struct l2cap_chan *c, *r = NULL;
> -
> - rcu_read_lock();
> + struct l2cap_chan *c;
>
> - list_for_each_entry_rcu(c, &conn->chan_l, list) {
> - if (c->scid == cid) {
> - r = c;
> - break;
> - }
> + list_for_each_entry(c, &conn->chan_l, list) {
> + if (c->scid == cid)
> + return c;
> }
> -
> - rcu_read_unlock();
> - return r;
> + return NULL;
> }
>
> /* Find channel with given SCID.
> @@ -115,36 +103,34 @@ static struct l2cap_chan *l2cap_get_chan_by_scid(struct l2cap_conn *conn, u16 ci
> {
> struct l2cap_chan *c;
>
> + mutex_lock(&conn->chan_lock);
> c = __l2cap_get_chan_by_scid(conn, cid);
> if (c)
> lock_sock(c->sk);
> + mutex_unlock(&conn->chan_lock);
> return c;
> }
>
> static struct l2cap_chan *__l2cap_get_chan_by_ident(struct l2cap_conn *conn, u8 ident)
> {
> - struct l2cap_chan *c, *r = NULL;
> -
> - rcu_read_lock();
> + struct l2cap_chan *c;
>
> - list_for_each_entry_rcu(c, &conn->chan_l, list) {
> - if (c->ident == ident) {
> - r = c;
> - break;
> - }
> + list_for_each_entry(c, &conn->chan_l, list) {
> + if (c->ident == ident)
> + return c;
> }
> -
> - rcu_read_unlock();
> - return r;
> + return NULL;
> }
>
> static inline struct l2cap_chan *l2cap_get_chan_by_ident(struct l2cap_conn *conn, u8 ident)
> {
> struct l2cap_chan *c;
>
> + mutex_lock(&conn->chan_lock);
> c = __l2cap_get_chan_by_ident(conn, ident);
> if (c)
> lock_sock(c->sk);
> + mutex_unlock(&conn->chan_lock);
> return c;
> }
>
> @@ -331,7 +317,9 @@ static void l2cap_chan_add(struct l2cap_conn *conn, struct l2cap_chan *chan)
>
> l2cap_chan_hold(chan);
>
> - list_add_rcu(&chan->list, &conn->chan_l);
> + mutex_lock(&conn->chan_lock);
> + list_add(&chan->list, &conn->chan_l);
> + mutex_unlock(&conn->chan_lock);
> }
>
> /* Delete channel.
> @@ -348,8 +336,7 @@ static void l2cap_chan_del(struct l2cap_chan *chan, int err)
>
> if (conn) {
> /* Delete from channel list */
> - list_del_rcu(&chan->list);
> - synchronize_rcu();
> + list_del(&chan->list);
>
> l2cap_chan_put(chan);
>
> @@ -400,10 +387,12 @@ static void l2cap_chan_cleanup_listen(struct sock *parent)
> /* Close not yet accepted channels */
> while ((sk = bt_accept_dequeue(parent, NULL))) {
> struct l2cap_chan *chan = l2cap_pi(sk)->chan;
> +
> __clear_chan_timer(chan);
> lock_sock(sk);
> l2cap_chan_close(chan, ECONNRESET);
> release_sock(sk);
> +
> chan->ops->close(chan->data);
> }
> }
> @@ -718,13 +707,13 @@ 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);
> @@ -804,7 +793,7 @@ 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.
> @@ -916,9 +905,9 @@ static void l2cap_conn_ready(struct l2cap_conn *conn)
> if (conn->hcon->out && conn->hcon->type == LE_LINK)
> smp_conn_security(conn, conn->hcon->pending_sec_level);
>
> - rcu_read_lock();
> + mutex_lock(&conn->chan_lock);
>
> - list_for_each_entry_rcu(chan, &conn->chan_l, list) {
> + list_for_each_entry(chan, &conn->chan_l, list) {
> struct sock *sk = chan->sk;
>
> bh_lock_sock(sk);
> @@ -938,7 +927,7 @@ static void l2cap_conn_ready(struct l2cap_conn *conn)
> bh_unlock_sock(sk);
> }
>
> - rcu_read_unlock();
> + mutex_unlock(&conn->chan_lock);
> }
>
> /* Notify sockets that we cannot guaranty reliability anymore */
> @@ -948,16 +937,16 @@ static void l2cap_conn_unreliable(struct l2cap_conn *conn, int err)
>
> 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(chan, &conn->chan_l, list) {
> struct sock *sk = chan->sk;
>
> if (test_bit(FLAG_FORCE_RELIABLE, &chan->flags))
> sk->sk_err = err;
> }
>
> - rcu_read_unlock();
> + mutex_unlock(&conn->chan_lock);
> }
>
> static void l2cap_info_timeout(struct work_struct *work)
> @@ -984,6 +973,8 @@ 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;
> @@ -993,6 +984,8 @@ 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)
> @@ -1050,6 +1043,7 @@ 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);
>
> @@ -1792,9 +1786,9 @@ static void l2cap_raw_recv(struct l2cap_conn *conn, struct sk_buff *skb)
>
> 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(chan, &conn->chan_l, list) {
> struct sock *sk = chan->sk;
> if (chan->chan_type != L2CAP_CHAN_RAW)
> continue;
> @@ -1810,7 +1804,7 @@ static void l2cap_raw_recv(struct l2cap_conn *conn, struct sk_buff *skb)
> kfree_skb(nskb);
> }
>
> - rcu_read_unlock();
> + mutex_unlock(&conn->chan_lock);
> }
>
> /* ---- L2CAP signalling commands ---- */
> @@ -4492,9 +4486,9 @@ int l2cap_security_cfm(struct hci_conn *hcon, u8 status, u8 encrypt)
> cancel_delayed_work(&conn->security_timer);
> }
>
> - rcu_read_lock();
> + mutex_lock(&conn->chan_lock);
>
> - list_for_each_entry_rcu(chan, &conn->chan_l, list) {
> + list_for_each_entry(chan, &conn->chan_l, list) {
> struct sock *sk = chan->sk;
>
> bh_lock_sock(sk);
> @@ -4574,7 +4568,7 @@ int l2cap_security_cfm(struct hci_conn *hcon, u8 status, u8 encrypt)
> bh_unlock_sock(sk);
> }
>
> - rcu_read_unlock();
> + mutex_unlock(&conn->chan_lock);
>
> return 0;
> }
Why don't you squash together patches 2, 3 and 4? Is there a reason?
Only with patch 2 the change becomes incomplete and prone to errors.
With patch 3 you add some needed changes but then adds an imbalance of
lock/release sock locks which is only solved in patch 4. Why?
Best regards,
--
Ulisses Furquim
ProFUSION embedded systems
http://profusion.mobi
Mobile: +55 19 9250 0942
Skype: ulissesffs
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