Return-Path: Message-ID: <1333082611.1870.227.camel@aeonflux> Subject: Re: [PATCHv2 1/2] Bluetooth: Add the l2cap_seq_list structure for tracking frames From: Marcel Holtmann To: Mat Martineau Cc: linux-bluetooth@vger.kernel.org, padovan@profusion.mobi, pkrystad@codeaurora.org Date: Fri, 30 Mar 2012 06:43:31 +0200 In-Reply-To: <1333067569-19247-2-git-send-email-mathewm@codeaurora.org> References: <1333067569-19247-1-git-send-email-mathewm@codeaurora.org> <1333067569-19247-2-git-send-email-mathewm@codeaurora.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-bluetooth-owner@vger.kernel.org List-ID: Hi Mat, > 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"); I think that see debug statement should go away. Do you really need them? > + 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); > } > Besides removing the debug statements, this looks good to me. Acked-by: Marcel Holtmann Regards Marcel