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Bluetooth: Change l2cap chan_list to use RCU
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This list has much more reads than writes, so RCU makes senses here, also
it avoid deadlock against the socket lock.

Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
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Gustavo F. Padovan committed Dec 18, 2011
1 parent 03a0019 commit 3d57dc6
Showing 1 changed file with 58 additions and 61 deletions.
119 changes: 58 additions & 61 deletions net/bluetooth/l2cap_core.c
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Original file line number Diff line number Diff line change
Expand Up @@ -89,24 +89,36 @@ static inline void chan_put(struct l2cap_chan *c)

static struct l2cap_chan *__l2cap_get_chan_by_dcid(struct l2cap_conn *conn, u16 cid)
{
struct l2cap_chan *c;
struct l2cap_chan *c, *r = NULL;

list_for_each_entry(c, &conn->chan_l, list) {
if (c->dcid == cid)
return c;
rcu_read_lock();

list_for_each_entry_rcu(c, &conn->chan_l, list) {
if (c->dcid == cid) {
r = c;
break;
}
}
return NULL;

rcu_read_unlock();
return r;
}

static struct l2cap_chan *__l2cap_get_chan_by_scid(struct l2cap_conn *conn, u16 cid)
{
struct l2cap_chan *c;
struct l2cap_chan *c, *r = NULL;

list_for_each_entry(c, &conn->chan_l, list) {
if (c->scid == cid)
return c;
rcu_read_lock();

list_for_each_entry_rcu(c, &conn->chan_l, list) {
if (c->scid == cid) {
r = c;
break;
}
}
return NULL;

rcu_read_unlock();
return r;
}

/* Find channel with given SCID.
Expand All @@ -115,34 +127,36 @@ 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;
struct l2cap_chan *c, *r = NULL;

list_for_each_entry(c, &conn->chan_l, list) {
if (c->ident == ident)
return c;
rcu_read_lock();

list_for_each_entry_rcu(c, &conn->chan_l, list) {
if (c->ident == ident) {
r = c;
break;
}
}
return NULL;

rcu_read_unlock();
return r;
}

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;
}

Expand Down Expand Up @@ -323,7 +337,7 @@ void l2cap_chan_destroy(struct l2cap_chan *chan)
chan_put(chan);
}

static void __l2cap_chan_add(struct l2cap_conn *conn, struct l2cap_chan *chan)
static void l2cap_chan_add(struct l2cap_conn *conn, struct l2cap_chan *chan)
{
BT_DBG("conn %p, psm 0x%2.2x, dcid 0x%4.4x", conn,
chan->psm, chan->dcid);
Expand Down Expand Up @@ -364,7 +378,7 @@ static void __l2cap_chan_add(struct l2cap_conn *conn, struct l2cap_chan *chan)

chan_hold(chan);

list_add(&chan->list, &conn->chan_l);
list_add_rcu(&chan->list, &conn->chan_l);
}

/* Delete channel.
Expand All @@ -381,9 +395,9 @@ static void l2cap_chan_del(struct l2cap_chan *chan, int err)

if (conn) {
/* Delete from channel list */
mutex_lock(&conn->chan_lock);
list_del(&chan->list);
mutex_unlock(&conn->chan_lock);
list_del_rcu(&chan->list);
synchronize_rcu();

chan_put(chan);

chan->conn = NULL;
Expand Down Expand Up @@ -750,13 +764,13 @@ 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, *tmp;
struct l2cap_chan *chan;

BT_DBG("conn %p", conn);

mutex_lock(&conn->chan_lock);
rcu_read_lock();

list_for_each_entry_safe(chan, tmp, &conn->chan_l, list) {
list_for_each_entry_rcu(chan, &conn->chan_l, list) {
struct sock *sk = chan->sk;

bh_lock_sock(sk);
Expand All @@ -780,9 +794,7 @@ static void l2cap_conn_start(struct l2cap_conn *conn)
&chan->conf_state)) {
/* l2cap_chan_close() calls list_del(chan)
* so release the lock */
mutex_unlock(&conn->chan_lock);
l2cap_chan_close(chan, ECONNRESET);
utex_lock(&conn->chan_lock);
bh_unlock_sock(sk);
continue;
}
Expand Down Expand Up @@ -838,7 +850,7 @@ static void l2cap_conn_start(struct l2cap_conn *conn)
bh_unlock_sock(sk);
}

mutex_unlock(&conn->chan_lock);
rcu_read_unlock();
}

/* Find socket with cid and source bdaddr.
Expand Down Expand Up @@ -903,24 +915,20 @@ static void l2cap_le_conn_ready(struct l2cap_conn *conn)

sk = chan->sk;

mutex_lock(&conn->chan_lock);

hci_conn_hold(conn->hcon);

bacpy(&bt_sk(sk)->src, conn->src);
bacpy(&bt_sk(sk)->dst, conn->dst);

bt_accept_enqueue(parent, sk);

__l2cap_chan_add(conn, chan);
l2cap_chan_add(conn, chan);

__set_chan_timer(chan, sk->sk_sndtimeo);

l2cap_state_change(chan, BT_CONNECTED);
parent->sk_data_ready(parent, 0);

mutex_unlock(&conn->chan_lock);

clean:
release_sock(parent);
}
Expand Down Expand Up @@ -954,9 +962,9 @@ 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);

mutex_lock(&conn->chan_lock);
rcu_read_lock();

list_for_each_entry(chan, &conn->chan_l, list) {
list_for_each_entry_rcu(chan, &conn->chan_l, list) {
struct sock *sk = chan->sk;

bh_lock_sock(sk);
Expand All @@ -976,7 +984,7 @@ static void l2cap_conn_ready(struct l2cap_conn *conn)
bh_unlock_sock(sk);
}

mutex_unlock(&conn->chan_lock);
rcu_read_unlock();
}

/* Notify sockets that we cannot guaranty reliability anymore */
Expand All @@ -986,16 +994,16 @@ static void l2cap_conn_unreliable(struct l2cap_conn *conn, int err)

BT_DBG("conn %p", conn);

mutex_lock(&conn->chan_lock);
rcu_read_lock();

list_for_each_entry(chan, &conn->chan_l, list) {
list_for_each_entry_rcu(chan, &conn->chan_l, list) {
struct sock *sk = chan->sk;

if (test_bit(FLAG_FORCE_RELIABLE, &chan->flags))
sk->sk_err = err;
}

mutex_unlock(&conn->chan_lock);
rcu_read_unlock();
}

static void l2cap_info_timeout(struct work_struct *work)
Expand Down Expand Up @@ -1087,7 +1095,6 @@ 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);

Expand All @@ -1102,13 +1109,6 @@ static struct l2cap_conn *l2cap_conn_add(struct hci_conn *hcon, u8 status)
return conn;
}

static inline void l2cap_chan_add(struct l2cap_conn *conn, struct l2cap_chan *chan)
{
mutex_lock(&conn->chan_lock);
__l2cap_chan_add(conn, chan);
mutex_unlock(&conn->chan_lock);
}

/* ---- Socket interface ---- */

/* Find socket with psm and source bdaddr.
Expand Down Expand Up @@ -1825,8 +1825,9 @@ static void l2cap_raw_recv(struct l2cap_conn *conn, struct sk_buff *skb)

BT_DBG("conn %p", conn);

mutex_lock(&conn->chan_lock);
list_for_each_entry(chan, &conn->chan_l, list) {
rcu_read_lock();

list_for_each_entry_rcu(chan, &conn->chan_l, list) {
struct sock *sk = chan->sk;
if (chan->chan_type != L2CAP_CHAN_RAW)
continue;
Expand All @@ -1841,7 +1842,8 @@ static void l2cap_raw_recv(struct l2cap_conn *conn, struct sk_buff *skb)
if (chan->ops->recv(chan->data, nskb))
kfree_skb(nskb);
}
mutex_unlock(&conn->chan_lock);

rcu_read_unlock();
}

/* ---- L2CAP signalling commands ---- */
Expand Down Expand Up @@ -2641,11 +2643,8 @@ static inline int l2cap_connect_req(struct l2cap_conn *conn, struct l2cap_cmd_hd

sk = chan->sk;

mutex_lock(&conn->chan_lock);

/* Check if we already have channel with that dcid */
if (__l2cap_get_chan_by_dcid(conn, scid)) {
mutex_unlock(&conn->chan_lock);
sock_set_flag(sk, SOCK_ZAPPED);
chan->ops->close(chan->data);
goto response;
Expand All @@ -2660,7 +2659,7 @@ static inline int l2cap_connect_req(struct l2cap_conn *conn, struct l2cap_cmd_hd

bt_accept_enqueue(parent, sk);

__l2cap_chan_add(conn, chan);
l2cap_chan_add(conn, chan);

dcid = chan->scid;

Expand Down Expand Up @@ -2691,8 +2690,6 @@ static inline int l2cap_connect_req(struct l2cap_conn *conn, struct l2cap_cmd_hd
status = L2CAP_CS_NO_INFO;
}

mutex_unlock(&conn->chan_lock);

response:
release_sock(parent);

Expand Down Expand Up @@ -4528,9 +4525,9 @@ static int l2cap_security_cfm(struct hci_conn *hcon, u8 status, u8 encrypt)
del_timer(&conn->security_timer);
}

mutex_lock(&conn->chan_lock);
rcu_read_lock();

list_for_each_entry(chan, &conn->chan_l, list) {
list_for_each_entry_rcu(chan, &conn->chan_l, list) {
struct sock *sk = chan->sk;

bh_lock_sock(sk);
Expand Down Expand Up @@ -4608,7 +4605,7 @@ static int l2cap_security_cfm(struct hci_conn *hcon, u8 status, u8 encrypt)
bh_unlock_sock(sk);
}

mutex_unlock(&conn->chan_lock);
rcu_read_unlock();

return 0;
}
Expand Down

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