Return-Path: From: Mat Martineau To: linux-bluetooth@vger.kernel.org Cc: padovan@profusion.mobi, pkrystad@codeaurora.org, marcel@holtmann.org, Mat Martineau Subject: [PATCHv2 1/2] Bluetooth: Add the l2cap_seq_list structure for tracking frames Date: Thu, 29 Mar 2012 17:32:48 -0700 Message-Id: <1333067569-19247-2-git-send-email-mathewm@codeaurora.org> In-Reply-To: <1333067569-19247-1-git-send-email-mathewm@codeaurora.org> References: <1333067569-19247-1-git-send-email-mathewm@codeaurora.org> Sender: linux-bluetooth-owner@vger.kernel.org List-ID: A sequence list is a data structure used to track frames that need to be retransmitted, and frames that have been requested for retransmission by the remote device. It can compactly represent a list of sequence numbers within the ERTM transmit window. Memory for the list is allocated once at connection time, and common operations in ERTM are O(1). Signed-off-by: Mat Martineau --- include/net/bluetooth/l2cap.h | 12 ++++ net/bluetooth/l2cap_core.c | 132 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 144 insertions(+) diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h index f6f0500..5d65b3d 100644 --- a/include/net/bluetooth/l2cap.h +++ b/include/net/bluetooth/l2cap.h @@ -407,6 +407,16 @@ struct l2cap_conn_param_update_rsp { #define L2CAP_CONN_PARAM_REJECTED 0x0001 /* ----- L2CAP channels and connections ----- */ +struct l2cap_seq_list { + __u16 head; + __u16 tail; + __u16 mask; + __u16 *list; +}; + +#define L2CAP_SEQ_LIST_CLEAR 0xFFFF +#define L2CAP_SEQ_LIST_TAIL 0x8000 + struct srej_list { __u16 tx_seq; struct list_head list; @@ -501,6 +511,8 @@ struct l2cap_chan { struct sk_buff *tx_send_head; struct sk_buff_head tx_q; struct sk_buff_head srej_q; + struct l2cap_seq_list srej_list; + struct l2cap_seq_list retrans_list; struct list_head srej_l; struct list_head list; diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index 3caff27..2414ddd 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -233,6 +233,134 @@ static inline void l2cap_chan_set_err(struct l2cap_chan *chan, int err) release_sock(sk); } +/* ---- L2CAP sequence number lists ---- */ + +/* For ERTM, ordered lists of sequence numbers must be tracked for + * SREJ requests that are received and for frames that are to be + * retransmitted. These seq_list functions implement a singly-linked + * list in an array, where membership in the list can also be checked + * in constant time. Items can also be added to the tail of the list + * and removed from the head in constant time, without further memory + * allocs or frees. + */ + +static int l2cap_seq_list_init(struct l2cap_seq_list *seq_list, u16 size) +{ + u16 alloc_size = 1; + int err = 0; + int i; + + /* Allocated size is a power of 2 to map sequence numbers + * (which may be up to 14 bits) in to a smaller array that is + * sized for the negotiated ERTM transmit windows. + */ + while (alloc_size && alloc_size <= size) + alloc_size <<= 1; + if (!alloc_size) + return -ENOMEM; + + seq_list->list = kzalloc(sizeof(u16) * alloc_size, GFP_KERNEL); + if (!seq_list->list) + return -ENOMEM; + + seq_list->mask = alloc_size - 1; + seq_list->head = L2CAP_SEQ_LIST_CLEAR; + seq_list->tail = L2CAP_SEQ_LIST_CLEAR; + for (i = 0; i < alloc_size; i++) + seq_list->list[i] = L2CAP_SEQ_LIST_CLEAR; + + return err; +} + +static inline void l2cap_seq_list_free(struct l2cap_seq_list *seq_list) +{ + kfree(seq_list->list); +} + +static inline bool l2cap_seq_list_contains(struct l2cap_seq_list *seq_list, + u16 seq) +{ + /* Constant-time check for list membership */ + return seq_list->list[seq & seq_list->mask] != L2CAP_SEQ_LIST_CLEAR; +} + +static u16 l2cap_seq_list_remove(struct l2cap_seq_list *seq_list, u16 seq) +{ + u16 mask = seq_list->mask; + + BT_DBG("seq_list %p, seq %d", seq_list, (int) seq); + + if (seq_list->head == L2CAP_SEQ_LIST_CLEAR) { + /* In case someone tries to pop the head of an empty list */ + BT_DBG("List empty"); + return L2CAP_SEQ_LIST_CLEAR; + } else if (seq_list->head == seq) { + /* Head can be removed in constant time */ + BT_DBG("Remove head"); + seq_list->head = seq_list->list[seq & mask]; + seq_list->list[seq & mask] = L2CAP_SEQ_LIST_CLEAR; + + if (seq_list->head == L2CAP_SEQ_LIST_TAIL) { + seq_list->head = L2CAP_SEQ_LIST_CLEAR; + seq_list->tail = L2CAP_SEQ_LIST_CLEAR; + } + } else { + /* Walk the list to find the sequence number */ + u16 prev = seq_list->head; + BT_DBG("Find and remove"); + while (seq_list->list[prev & mask] != seq) { + prev = seq_list->list[prev & mask]; + if (prev == L2CAP_SEQ_LIST_TAIL) { + BT_DBG("seq %d not in list", (int) seq); + return L2CAP_SEQ_LIST_CLEAR; + } + } + + /* Unlink the number from the list and clear it */ + seq_list->list[prev & mask] = seq_list->list[seq & mask]; + seq_list->list[seq & mask] = L2CAP_SEQ_LIST_CLEAR; + if (seq_list->tail == seq) + seq_list->tail = prev; + } + return seq; +} + +static u16 l2cap_seq_list_pop(struct l2cap_seq_list *seq_list) +{ + /* Remove the head in constant time */ + return l2cap_seq_list_remove(seq_list, seq_list->head); +} + +static void l2cap_seq_list_clear(struct l2cap_seq_list *seq_list) +{ + if (seq_list->head != L2CAP_SEQ_LIST_CLEAR) { + u16 i; + for (i = 0; i <= seq_list->mask; i++) + seq_list->list[i] = L2CAP_SEQ_LIST_CLEAR; + + seq_list->head = L2CAP_SEQ_LIST_CLEAR; + seq_list->tail = L2CAP_SEQ_LIST_CLEAR; + } +} + +static void l2cap_seq_list_append(struct l2cap_seq_list *seq_list, u16 seq) +{ + u16 mask = seq_list->mask; + + /* All appends happen in constant time */ + BT_DBG("seq_list %p, seq %d", seq_list, (int) seq); + + if (seq_list->list[seq & mask] == L2CAP_SEQ_LIST_CLEAR) { + if (seq_list->tail == L2CAP_SEQ_LIST_CLEAR) + seq_list->head = seq; + else + seq_list->list[seq_list->tail & mask] = seq; + + seq_list->tail = seq; + seq_list->list[seq & mask] = L2CAP_SEQ_LIST_TAIL; + } +} + static void l2cap_chan_timeout(struct work_struct *work) { struct l2cap_chan *chan = container_of(work, struct l2cap_chan, @@ -404,6 +532,8 @@ static void l2cap_chan_del(struct l2cap_chan *chan, int err) skb_queue_purge(&chan->srej_q); + l2cap_seq_list_free(&chan->srej_list); + l2cap_seq_list_free(&chan->retrans_list); list_for_each_entry_safe(l, tmp, &chan->srej_l, list) { list_del(&l->list); kfree(l); @@ -2052,6 +2182,8 @@ static inline void l2cap_ertm_init(struct l2cap_chan *chan) skb_queue_head_init(&chan->srej_q); + l2cap_seq_list_init(&chan->srej_list, chan->tx_win); + l2cap_seq_list_init(&chan->retrans_list, chan->remote_tx_win); INIT_LIST_HEAD(&chan->srej_l); } -- 1.7.9.4 -- Mat Martineau Employee of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum