Return-Path: Date: Wed, 6 Jul 2011 16:01:43 -0700 (PDT) From: Mat Martineau To: Gustavo Padovan cc: linux-bluetooth@vger.kernel.org Subject: Re: [PATCH v2 2/3] Bluetooth: Use event-driven approach for handling ERTM receive buffer In-Reply-To: <20110706223635.GD7786@joana> Message-ID: References: <1309989272-24103-1-git-send-email-mathewm@codeaurora.org> <1309989272-24103-3-git-send-email-mathewm@codeaurora.org> <20110706223635.GD7786@joana> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-bluetooth-owner@vger.kernel.org List-ID: Hi Gustavo - On Wed, 6 Jul 2011, Gustavo Padovan wrote: > Hi Mat, > > * Mat Martineau [2011-07-06 14:54:31 -0700]: > >> This change moves most L2CAP ERTM receive buffer handling out of the >> L2CAP core and in to the socket code. It's up to the higher layer >> (the socket code, in this case) to tell the core when its buffer is >> full or has space available. The recv op should always accept >> incoming ERTM data or else the connection will go down. >> >> Within the socket layer, an skb that does not fit in the socket >> receive buffer will be temporarily stored. When the socket is read >> from, that skb will be placed in the receive buffer if possible. Once >> adequate buffer space becomes available, the L2CAP core is informed >> and the ERTM local busy state is cleared. >> >> Receive buffer management for non-ERTM modes is unchanged. >> >> Signed-off-by: Mat Martineau >> --- >> include/net/bluetooth/l2cap.h | 2 + >> net/bluetooth/l2cap_core.c | 41 ++++++++++++++++--------- >> net/bluetooth/l2cap_sock.c | 66 ++++++++++++++++++++++++++++++++++++++-- >> 3 files changed, 90 insertions(+), 19 deletions(-) >> >> diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h >> index 9c18e55..66b8d96 100644 >> --- a/include/net/bluetooth/l2cap.h >> +++ b/include/net/bluetooth/l2cap.h >> @@ -422,6 +422,7 @@ struct l2cap_conn { >> struct l2cap_pinfo { >> struct bt_sock bt; >> struct l2cap_chan *chan; >> + struct sk_buff *rx_busy_skb; >> }; >> >> enum { >> @@ -498,5 +499,6 @@ void l2cap_chan_close(struct l2cap_chan *chan, int reason); >> void l2cap_chan_destroy(struct l2cap_chan *chan); >> int l2cap_chan_connect(struct l2cap_chan *chan); >> int l2cap_chan_send(struct l2cap_chan *chan, struct msghdr *msg, size_t len); >> +void l2cap_chan_busy(struct l2cap_chan *chan, int busy); >> >> #endif /* __L2CAP_H */ >> diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c >> index f7ada4a..ea9c7d0 100644 >> --- a/net/bluetooth/l2cap_core.c >> +++ b/net/bluetooth/l2cap_core.c >> @@ -3350,21 +3350,21 @@ static int l2cap_push_rx_skb(struct l2cap_chan *chan, struct sk_buff *skb, u16 c >> } >> >> err = l2cap_ertm_reassembly_sdu(chan, skb, control); >> - if (err >= 0) { >> - chan->buffer_seq = (chan->buffer_seq + 1) % 64; >> - return err; >> - } >> - >> - l2cap_ertm_enter_local_busy(chan); >> - >> - bt_cb(skb)->sar = control >> L2CAP_CTRL_SAR_SHIFT; >> - __skb_queue_tail(&chan->busy_q, skb); >> - >> - queue_work(_busy_wq, &chan->busy_work); >> + chan->buffer_seq = (chan->buffer_seq + 1) % 64; >> >> return err; >> } >> >> +void l2cap_chan_busy(struct l2cap_chan *chan, int busy) >> +{ >> + if (chan->mode == L2CAP_MODE_ERTM) { >> + if (busy) >> + l2cap_ertm_enter_local_busy(chan); >> + else >> + l2cap_ertm_exit_local_busy(chan); >> + } >> +} >> + >> static int l2cap_streaming_reassembly_sdu(struct l2cap_chan *chan, struct sk_buff *skb, u16 control) >> { >> struct sk_buff *_skb; >> @@ -3463,13 +3463,22 @@ static void l2cap_check_srej_gap(struct l2cap_chan *chan, u8 tx_seq) >> struct sk_buff *skb; >> u16 control; >> >> - while ((skb = skb_peek(&chan->srej_q))) { >> + while ((skb = skb_peek(&chan->srej_q)) && >> + !test_bit(CONN_LOCAL_BUSY, &chan->conn_state)) { >> + int err; >> + >> if (bt_cb(skb)->tx_seq != tx_seq) >> break; >> >> skb = skb_dequeue(&chan->srej_q); >> control = bt_cb(skb)->sar << L2CAP_CTRL_SAR_SHIFT; >> - l2cap_ertm_reassembly_sdu(chan, skb, control); >> + err = l2cap_ertm_reassembly_sdu(chan, skb, control); >> + >> + if (err < 0) { >> + l2cap_send_disconn_req(chan->conn, chan, ECONNRESET); >> + break; >> + } >> + >> chan->buffer_seq_srej = >> (chan->buffer_seq_srej + 1) % 64; >> tx_seq = (tx_seq + 1) % 64; >> @@ -3625,8 +3634,10 @@ expected: >> } >> >> err = l2cap_push_rx_skb(chan, skb, rx_control); >> - if (err < 0) >> - return 0; >> + if (err < 0) { >> + l2cap_send_disconn_req(chan->conn, chan, ECONNRESET); >> + return err; >> + } >> >> if (rx_control & L2CAP_CTRL_FINAL) { >> if (!test_and_clear_bit(CONN_REJ_ACT, &chan->conn_state)) >> diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c >> index 39082d4..9bf7313 100644 >> --- a/net/bluetooth/l2cap_sock.c >> +++ b/net/bluetooth/l2cap_sock.c >> @@ -711,13 +711,15 @@ static int l2cap_sock_sendmsg(struct kiocb *iocb, struct socket *sock, struct ms >> static int l2cap_sock_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *msg, size_t len, int flags) >> { >> struct sock *sk = sock->sk; >> + struct l2cap_pinfo *pi = l2cap_pi(sk); >> + int err; >> >> lock_sock(sk); >> >> if (sk->sk_state == BT_CONNECT2 && bt_sk(sk)->defer_setup) { >> sk->sk_state = BT_CONFIG; >> >> - __l2cap_connect_rsp_defer(l2cap_pi(sk)->chan); >> + __l2cap_connect_rsp_defer(pi->chan); >> release_sock(sk); >> return 0; >> } >> @@ -725,9 +727,38 @@ static int l2cap_sock_recvmsg(struct kiocb *iocb, struct socket *sock, struct ms >> release_sock(sk); >> >> if (sock->type == SOCK_STREAM) >> - return bt_sock_stream_recvmsg(iocb, sock, msg, len, flags); >> + err = bt_sock_stream_recvmsg(iocb, sock, msg, len, flags); >> + else >> + err = bt_sock_recvmsg(iocb, sock, msg, len, flags); >> + >> + if (pi->chan->mode == L2CAP_MODE_ERTM) { > > if (pi->chan->mode != L2CAP_MODE_ERTM) { > return err; > > lock_sock()... Ok. >> + int threshold; >> + >> + /* Attempt to put pending rx data in the socket buffer */ >> + >> + lock_sock(sk); >> + if (pi->rx_busy_skb) { >> + int queue_err; >> + queue_err = sock_queue_rcv_skb(sk, pi->rx_busy_skb); >> + >> + if (!queue_err) >> + pi->rx_busy_skb = NULL; > > if (!sock_queue_rcv_skb()) > pi->rx_busy_skb = NULL; > else > return err; > > What I understood is that if sock_queue_rcv_skb() fails there is no need to > check if there is available space in the buffer, then we just return. The > locks also needs to be released. You're right - it's better to make sure we don't exit local busy in this case. >> + } >> + >> + /* Restore data flow when half of the receive buffer is >> + * available. This avoids resending large numbers of >> + * frames. >> + */ >> + threshold = sk->sk_rcvbuf >> 1; >> + if (test_bit(CONN_LOCAL_BUSY, &pi->chan->conn_state) && >> + !pi->rx_busy_skb && >> + atomic_read(&sk->sk_rmem_alloc) <= threshold) >> + l2cap_chan_busy(pi->chan, 0); > > Then this if can be just > > if (atomic_read(sk_rmem_alloc) <= sk_rcvbuf >> 1) > l2cap_chan_busy(pi->chan, 0); > It's still important to see if the channel is currently LOCAL_BUSY, this code path will be executed every time an ERTM socket is read from (busy or not). >> + >> + release_sock(sk); >> + } >> >> - return bt_sock_recvmsg(iocb, sock, msg, len, flags); >> + return err; >> } >> >> /* Kill socket (only if zapped and orphan) >> @@ -811,9 +842,31 @@ static struct l2cap_chan *l2cap_sock_new_connection_cb(void *data) >> >> static int l2cap_sock_recv_cb(void *data, struct sk_buff *skb) >> { >> + int err; >> struct sock *sk = data; >> + struct l2cap_pinfo *pi = l2cap_pi(sk); >> + >> + if (pi->rx_busy_skb) >> + return -ENOMEM; >> >> - return sock_queue_rcv_skb(sk, skb); >> + err = sock_queue_rcv_skb(sk, skb); >> + >> + /* For ERTM, handle one skb that doesn't fit into the recv >> + * buffer. This is important to do because the data frames >> + * have already been acked, so the skb cannot be discarded. >> + * >> + * Notify the l2cap core that the buffer is full, so the >> + * LOCAL_BUSY state is entered and no more frames are >> + * acked and reassembled until there is buffer space >> + * available. >> + */ >> + if (err < 0 && pi->chan->mode == L2CAP_MODE_ERTM) { >> + pi->rx_busy_skb = skb; >> + l2cap_chan_busy(pi->chan, 1); >> + err = 0; >> + } >> + >> + return err; > > You always return 0 here, remove err; It might not be 0 in basic mode or streaming mode, or raw. In these cases, the error code needs to be returned so the skb is freed. Thanks for the feedback, I'll get to work on v3. -- Mat Martineau Employee of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum