linux/net/tipc/bcast.c
Per Liden b97bf3fd8f [TIPC] Initial merge
TIPC (Transparent Inter Process Communication) is a protocol designed for
intra cluster communication. For more information see
http://tipc.sourceforge.net

Signed-off-by: Per Liden <per.liden@nospam.ericsson.com>
2006-01-12 14:06:31 -08:00

804 lines
20 KiB
C

/*
* net/tipc/bcast.c: TIPC broadcast code
*
* Copyright (c) 2003-2005, Ericsson Research Canada
* Copyright (c) 2004, Intel Corporation.
* Copyright (c) 2005, Wind River Systems
* Copyright (c) 2005-2006, Ericsson AB
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* Neither the names of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include "core.h"
#include "msg.h"
#include "dbg.h"
#include "link.h"
#include "net.h"
#include "node.h"
#include "port.h"
#include "addr.h"
#include "node_subscr.h"
#include "name_distr.h"
#include "bearer.h"
#include "name_table.h"
#include "bcast.h"
#define MAX_PKT_DEFAULT_MCAST 1500 /* bcast link max packet size (fixed) */
#define BCLINK_WIN_DEFAULT 20 /* bcast link window size (default) */
#define BCLINK_LOG_BUF_SIZE 0
/**
* struct bcbearer_pair - a pair of bearers used by broadcast link
* @primary: pointer to primary bearer
* @secondary: pointer to secondary bearer
*
* Bearers must have same priority and same set of reachable destinations
* to be paired.
*/
struct bcbearer_pair {
struct bearer *primary;
struct bearer *secondary;
};
/**
* struct bcbearer - bearer used by broadcast link
* @bearer: (non-standard) broadcast bearer structure
* @media: (non-standard) broadcast media structure
* @bpairs: array of bearer pairs
* @bpairs_temp: array of bearer pairs used during creation of "bpairs"
*/
struct bcbearer {
struct bearer bearer;
struct media media;
struct bcbearer_pair bpairs[MAX_BEARERS];
struct bcbearer_pair bpairs_temp[TIPC_NUM_LINK_PRI];
};
/**
* struct bclink - link used for broadcast messages
* @link: (non-standard) broadcast link structure
* @node: (non-standard) node structure representing b'cast link's peer node
*
* Handles sequence numbering, fragmentation, bundling, etc.
*/
struct bclink {
struct link link;
struct node node;
};
static struct bcbearer *bcbearer = NULL;
static struct bclink *bclink = NULL;
static struct link *bcl = NULL;
static spinlock_t bc_lock = SPIN_LOCK_UNLOCKED;
char bc_link_name[] = "multicast-link";
static inline u32 buf_seqno(struct sk_buff *buf)
{
return msg_seqno(buf_msg(buf));
}
static inline u32 bcbuf_acks(struct sk_buff *buf)
{
return (u32)TIPC_SKB_CB(buf)->handle;
}
static inline void bcbuf_set_acks(struct sk_buff *buf, u32 acks)
{
TIPC_SKB_CB(buf)->handle = (void *)acks;
}
static inline void bcbuf_decr_acks(struct sk_buff *buf)
{
bcbuf_set_acks(buf, bcbuf_acks(buf) - 1);
}
/**
* bclink_set_gap - set gap according to contents of current deferred pkt queue
*
* Called with 'node' locked, bc_lock unlocked
*/
static inline void bclink_set_gap(struct node *n_ptr)
{
struct sk_buff *buf = n_ptr->bclink.deferred_head;
n_ptr->bclink.gap_after = n_ptr->bclink.gap_to =
mod(n_ptr->bclink.last_in);
if (unlikely(buf != NULL))
n_ptr->bclink.gap_to = mod(buf_seqno(buf) - 1);
}
/**
* bclink_ack_allowed - test if ACK or NACK message can be sent at this moment
*
* This mechanism endeavours to prevent all nodes in network from trying
* to ACK or NACK at the same time.
*
* Note: TIPC uses a different trigger to distribute ACKs than it does to
* distribute NACKs, but tries to use the same spacing (divide by 16).
*/
static inline int bclink_ack_allowed(u32 n)
{
return((n % TIPC_MIN_LINK_WIN) == tipc_own_tag);
}
/**
* bclink_retransmit_pkt - retransmit broadcast packets
* @after: sequence number of last packet to *not* retransmit
* @to: sequence number of last packet to retransmit
*
* Called with 'node' locked, bc_lock unlocked
*/
static void bclink_retransmit_pkt(u32 after, u32 to)
{
struct sk_buff *buf;
spin_lock_bh(&bc_lock);
buf = bcl->first_out;
while (buf && less_eq(buf_seqno(buf), after)) {
buf = buf->next;
}
if (buf != NULL)
link_retransmit(bcl, buf, mod(to - after));
spin_unlock_bh(&bc_lock);
}
/**
* bclink_acknowledge - handle acknowledgement of broadcast packets
* @n_ptr: node that sent acknowledgement info
* @acked: broadcast sequence # that has been acknowledged
*
* Node is locked, bc_lock unlocked.
*/
void bclink_acknowledge(struct node *n_ptr, u32 acked)
{
struct sk_buff *crs;
struct sk_buff *next;
unsigned int released = 0;
if (less_eq(acked, n_ptr->bclink.acked))
return;
spin_lock_bh(&bc_lock);
/* Skip over packets that node has previously acknowledged */
crs = bcl->first_out;
while (crs && less_eq(buf_seqno(crs), n_ptr->bclink.acked)) {
crs = crs->next;
}
/* Update packets that node is now acknowledging */
while (crs && less_eq(buf_seqno(crs), acked)) {
next = crs->next;
bcbuf_decr_acks(crs);
if (bcbuf_acks(crs) == 0) {
bcl->first_out = next;
bcl->out_queue_size--;
buf_discard(crs);
released = 1;
}
crs = next;
}
n_ptr->bclink.acked = acked;
/* Try resolving broadcast link congestion, if necessary */
if (unlikely(bcl->next_out))
link_push_queue(bcl);
if (unlikely(released && !list_empty(&bcl->waiting_ports)))
link_wakeup_ports(bcl, 0);
spin_unlock_bh(&bc_lock);
}
/**
* bclink_send_ack - unicast an ACK msg
*
* net_lock and node lock set
*/
static void bclink_send_ack(struct node *n_ptr)
{
struct link *l_ptr = n_ptr->active_links[n_ptr->addr & 1];
if (l_ptr != NULL)
link_send_proto_msg(l_ptr, STATE_MSG, 0, 0, 0, 0, 0);
}
/**
* bclink_send_nack- broadcast a NACK msg
*
* net_lock and node lock set
*/
static void bclink_send_nack(struct node *n_ptr)
{
struct sk_buff *buf;
struct tipc_msg *msg;
if (!less(n_ptr->bclink.gap_after, n_ptr->bclink.gap_to))
return;
buf = buf_acquire(INT_H_SIZE);
if (buf) {
msg = buf_msg(buf);
msg_init(msg, BCAST_PROTOCOL, STATE_MSG,
TIPC_OK, INT_H_SIZE, n_ptr->addr);
msg_set_mc_netid(msg, tipc_net_id);
msg_set_bcast_ack(msg, mod(n_ptr->bclink.last_in));
msg_set_bcgap_after(msg, n_ptr->bclink.gap_after);
msg_set_bcgap_to(msg, n_ptr->bclink.gap_to);
msg_set_bcast_tag(msg, tipc_own_tag);
if (bearer_send(&bcbearer->bearer, buf, 0)) {
bcl->stats.sent_nacks++;
buf_discard(buf);
} else {
bearer_schedule(bcl->b_ptr, bcl);
bcl->proto_msg_queue = buf;
bcl->stats.bearer_congs++;
}
/*
* Ensure we doesn't send another NACK msg to the node
* until 16 more deferred messages arrive from it
* (i.e. helps prevent all nodes from NACK'ing at same time)
*/
n_ptr->bclink.nack_sync = tipc_own_tag;
}
}
/**
* bclink_check_gap - send a NACK if a sequence gap exists
*
* net_lock and node lock set
*/
void bclink_check_gap(struct node *n_ptr, u32 last_sent)
{
if (!n_ptr->bclink.supported ||
less_eq(last_sent, mod(n_ptr->bclink.last_in)))
return;
bclink_set_gap(n_ptr);
if (n_ptr->bclink.gap_after == n_ptr->bclink.gap_to)
n_ptr->bclink.gap_to = last_sent;
bclink_send_nack(n_ptr);
}
/**
* bclink_peek_nack - process a NACK msg meant for another node
*
* Only net_lock set.
*/
void bclink_peek_nack(u32 dest, u32 sender_tag, u32 gap_after, u32 gap_to)
{
struct node *n_ptr = node_find(dest);
u32 my_after, my_to;
if (unlikely(!n_ptr || !node_is_up(n_ptr)))
return;
node_lock(n_ptr);
/*
* Modify gap to suppress unnecessary NACKs from this node
*/
my_after = n_ptr->bclink.gap_after;
my_to = n_ptr->bclink.gap_to;
if (less_eq(gap_after, my_after)) {
if (less(my_after, gap_to) && less(gap_to, my_to))
n_ptr->bclink.gap_after = gap_to;
else if (less_eq(my_to, gap_to))
n_ptr->bclink.gap_to = n_ptr->bclink.gap_after;
} else if (less_eq(gap_after, my_to)) {
if (less_eq(my_to, gap_to))
n_ptr->bclink.gap_to = gap_after;
} else {
/*
* Expand gap if missing bufs not in deferred queue:
*/
struct sk_buff *buf = n_ptr->bclink.deferred_head;
u32 prev = n_ptr->bclink.gap_to;
for (; buf; buf = buf->next) {
u32 seqno = buf_seqno(buf);
if (mod(seqno - prev) != 1)
buf = NULL;
if (seqno == gap_after)
break;
prev = seqno;
}
if (buf == NULL)
n_ptr->bclink.gap_to = gap_after;
}
/*
* Some nodes may send a complementary NACK now:
*/
if (bclink_ack_allowed(sender_tag + 1)) {
if (n_ptr->bclink.gap_to != n_ptr->bclink.gap_after) {
bclink_send_nack(n_ptr);
bclink_set_gap(n_ptr);
}
}
node_unlock(n_ptr);
}
/**
* bclink_send_msg - broadcast a packet to all nodes in cluster
*/
int bclink_send_msg(struct sk_buff *buf)
{
int res;
spin_lock_bh(&bc_lock);
res = link_send_buf(bcl, buf);
if (unlikely(res == -ELINKCONG))
buf_discard(buf);
else
bcl->stats.sent_info++;
if (bcl->out_queue_size > bcl->stats.max_queue_sz)
bcl->stats.max_queue_sz = bcl->out_queue_size;
bcl->stats.queue_sz_counts++;
bcl->stats.accu_queue_sz += bcl->out_queue_size;
spin_unlock_bh(&bc_lock);
return res;
}
/**
* bclink_recv_pkt - receive a broadcast packet, and deliver upwards
*
* net_lock is read_locked, no other locks set
*/
void bclink_recv_pkt(struct sk_buff *buf)
{
struct tipc_msg *msg = buf_msg(buf);
struct node* node = node_find(msg_prevnode(msg));
u32 next_in;
u32 seqno;
struct sk_buff *deferred;
msg_dbg(msg, "<BC<<<");
if (unlikely(!node || !node_is_up(node) || !node->bclink.supported ||
(msg_mc_netid(msg) != tipc_net_id))) {
buf_discard(buf);
return;
}
if (unlikely(msg_user(msg) == BCAST_PROTOCOL)) {
msg_dbg(msg, "<BCNACK<<<");
if (msg_destnode(msg) == tipc_own_addr) {
node_lock(node);
bclink_acknowledge(node, msg_bcast_ack(msg));
node_unlock(node);
bcl->stats.recv_nacks++;
bclink_retransmit_pkt(msg_bcgap_after(msg),
msg_bcgap_to(msg));
} else {
bclink_peek_nack(msg_destnode(msg),
msg_bcast_tag(msg),
msg_bcgap_after(msg),
msg_bcgap_to(msg));
}
buf_discard(buf);
return;
}
node_lock(node);
receive:
deferred = node->bclink.deferred_head;
next_in = mod(node->bclink.last_in + 1);
seqno = msg_seqno(msg);
if (likely(seqno == next_in)) {
bcl->stats.recv_info++;
node->bclink.last_in++;
bclink_set_gap(node);
if (unlikely(bclink_ack_allowed(seqno))) {
bclink_send_ack(node);
bcl->stats.sent_acks++;
}
if (likely(msg_isdata(msg))) {
node_unlock(node);
port_recv_mcast(buf, NULL);
} else if (msg_user(msg) == MSG_BUNDLER) {
bcl->stats.recv_bundles++;
bcl->stats.recv_bundled += msg_msgcnt(msg);
node_unlock(node);
link_recv_bundle(buf);
} else if (msg_user(msg) == MSG_FRAGMENTER) {
bcl->stats.recv_fragments++;
if (link_recv_fragment(&node->bclink.defragm,
&buf, &msg))
bcl->stats.recv_fragmented++;
node_unlock(node);
net_route_msg(buf);
} else {
node_unlock(node);
net_route_msg(buf);
}
if (deferred && (buf_seqno(deferred) == mod(next_in + 1))) {
node_lock(node);
buf = deferred;
msg = buf_msg(buf);
node->bclink.deferred_head = deferred->next;
goto receive;
}
return;
} else if (less(next_in, seqno)) {
u32 gap_after = node->bclink.gap_after;
u32 gap_to = node->bclink.gap_to;
if (link_defer_pkt(&node->bclink.deferred_head,
&node->bclink.deferred_tail,
buf)) {
node->bclink.nack_sync++;
bcl->stats.deferred_recv++;
if (seqno == mod(gap_after + 1))
node->bclink.gap_after = seqno;
else if (less(gap_after, seqno) && less(seqno, gap_to))
node->bclink.gap_to = seqno;
}
if (bclink_ack_allowed(node->bclink.nack_sync)) {
if (gap_to != gap_after)
bclink_send_nack(node);
bclink_set_gap(node);
}
} else {
bcl->stats.duplicates++;
buf_discard(buf);
}
node_unlock(node);
}
u32 bclink_get_last_sent(void)
{
u32 last_sent = mod(bcl->next_out_no - 1);
if (bcl->next_out)
last_sent = mod(buf_seqno(bcl->next_out) - 1);
return last_sent;
}
u32 bclink_acks_missing(struct node *n_ptr)
{
return (n_ptr->bclink.supported &&
(bclink_get_last_sent() != n_ptr->bclink.acked));
}
/**
* bcbearer_send - send a packet through the broadcast pseudo-bearer
*
* Send through as many bearers as necessary to reach all nodes
* that support TIPC multicasting.
*
* Returns 0 if packet sent successfully, non-zero if not
*/
int bcbearer_send(struct sk_buff *buf,
struct tipc_bearer *unused1,
struct tipc_media_addr *unused2)
{
static int send_count = 0;
struct node_map remains;
struct node_map remains_new;
int bp_index;
int swap_time;
/* Prepare buffer for broadcasting (if first time trying to send it) */
if (likely(!msg_non_seq(buf_msg(buf)))) {
struct tipc_msg *msg;
assert(cluster_bcast_nodes.count != 0);
bcbuf_set_acks(buf, cluster_bcast_nodes.count);
msg = buf_msg(buf);
msg_set_non_seq(msg);
msg_set_mc_netid(msg, tipc_net_id);
}
/* Determine if bearer pairs should be swapped following this attempt */
if ((swap_time = (++send_count >= 10)))
send_count = 0;
/* Send buffer over bearers until all targets reached */
remains = cluster_bcast_nodes;
for (bp_index = 0; bp_index < MAX_BEARERS; bp_index++) {
struct bearer *p = bcbearer->bpairs[bp_index].primary;
struct bearer *s = bcbearer->bpairs[bp_index].secondary;
if (!p)
break; /* no more bearers to try */
nmap_diff(&remains, &p->nodes, &remains_new);
if (remains_new.count == remains.count)
continue; /* bearer pair doesn't add anything */
if (!p->publ.blocked &&
!p->media->send_msg(buf, &p->publ, &p->media->bcast_addr)) {
if (swap_time && s && !s->publ.blocked)
goto swap;
else
goto update;
}
if (!s || s->publ.blocked ||
s->media->send_msg(buf, &s->publ, &s->media->bcast_addr))
continue; /* unable to send using bearer pair */
swap:
bcbearer->bpairs[bp_index].primary = s;
bcbearer->bpairs[bp_index].secondary = p;
update:
if (remains_new.count == 0)
return TIPC_OK;
remains = remains_new;
}
/* Unable to reach all targets */
bcbearer->bearer.publ.blocked = 1;
bcl->stats.bearer_congs++;
return ~TIPC_OK;
}
/**
* bcbearer_sort - create sets of bearer pairs used by broadcast bearer
*/
void bcbearer_sort(void)
{
struct bcbearer_pair *bp_temp = bcbearer->bpairs_temp;
struct bcbearer_pair *bp_curr;
int b_index;
int pri;
spin_lock_bh(&bc_lock);
/* Group bearers by priority (can assume max of two per priority) */
memset(bp_temp, 0, sizeof(bcbearer->bpairs_temp));
for (b_index = 0; b_index < MAX_BEARERS; b_index++) {
struct bearer *b = &bearers[b_index];
if (!b->active || !b->nodes.count)
continue;
if (!bp_temp[b->priority].primary)
bp_temp[b->priority].primary = b;
else
bp_temp[b->priority].secondary = b;
}
/* Create array of bearer pairs for broadcasting */
bp_curr = bcbearer->bpairs;
memset(bcbearer->bpairs, 0, sizeof(bcbearer->bpairs));
for (pri = (TIPC_NUM_LINK_PRI - 1); pri >= 0; pri--) {
if (!bp_temp[pri].primary)
continue;
bp_curr->primary = bp_temp[pri].primary;
if (bp_temp[pri].secondary) {
if (nmap_equal(&bp_temp[pri].primary->nodes,
&bp_temp[pri].secondary->nodes)) {
bp_curr->secondary = bp_temp[pri].secondary;
} else {
bp_curr++;
bp_curr->primary = bp_temp[pri].secondary;
}
}
bp_curr++;
}
spin_unlock_bh(&bc_lock);
}
/**
* bcbearer_push - resolve bearer congestion
*
* Forces bclink to push out any unsent packets, until all packets are gone
* or congestion reoccurs.
* No locks set when function called
*/
void bcbearer_push(void)
{
struct bearer *b_ptr;
spin_lock_bh(&bc_lock);
b_ptr = &bcbearer->bearer;
if (b_ptr->publ.blocked) {
b_ptr->publ.blocked = 0;
bearer_lock_push(b_ptr);
}
spin_unlock_bh(&bc_lock);
}
int bclink_stats(char *buf, const u32 buf_size)
{
struct print_buf pb;
if (!bcl)
return 0;
printbuf_init(&pb, buf, buf_size);
spin_lock_bh(&bc_lock);
tipc_printf(&pb, "Link <%s>\n"
" Window:%u packets\n",
bcl->name, bcl->queue_limit[0]);
tipc_printf(&pb, " RX packets:%u fragments:%u/%u bundles:%u/%u\n",
bcl->stats.recv_info,
bcl->stats.recv_fragments,
bcl->stats.recv_fragmented,
bcl->stats.recv_bundles,
bcl->stats.recv_bundled);
tipc_printf(&pb, " TX packets:%u fragments:%u/%u bundles:%u/%u\n",
bcl->stats.sent_info,
bcl->stats.sent_fragments,
bcl->stats.sent_fragmented,
bcl->stats.sent_bundles,
bcl->stats.sent_bundled);
tipc_printf(&pb, " RX naks:%u defs:%u dups:%u\n",
bcl->stats.recv_nacks,
bcl->stats.deferred_recv,
bcl->stats.duplicates);
tipc_printf(&pb, " TX naks:%u acks:%u dups:%u\n",
bcl->stats.sent_nacks,
bcl->stats.sent_acks,
bcl->stats.retransmitted);
tipc_printf(&pb, " Congestion bearer:%u link:%u Send queue max:%u avg:%u\n",
bcl->stats.bearer_congs,
bcl->stats.link_congs,
bcl->stats.max_queue_sz,
bcl->stats.queue_sz_counts
? (bcl->stats.accu_queue_sz / bcl->stats.queue_sz_counts)
: 0);
spin_unlock_bh(&bc_lock);
return printbuf_validate(&pb);
}
int bclink_reset_stats(void)
{
if (!bcl)
return -ENOPROTOOPT;
spin_lock_bh(&bc_lock);
memset(&bcl->stats, 0, sizeof(bcl->stats));
spin_unlock_bh(&bc_lock);
return TIPC_OK;
}
int bclink_set_queue_limits(u32 limit)
{
if (!bcl)
return -ENOPROTOOPT;
if ((limit < TIPC_MIN_LINK_WIN) || (limit > TIPC_MAX_LINK_WIN))
return -EINVAL;
spin_lock_bh(&bc_lock);
link_set_queue_limits(bcl, limit);
spin_unlock_bh(&bc_lock);
return TIPC_OK;
}
int bclink_init(void)
{
bcbearer = kmalloc(sizeof(*bcbearer), GFP_ATOMIC);
bclink = kmalloc(sizeof(*bclink), GFP_ATOMIC);
if (!bcbearer || !bclink) {
nomem:
warn("Memory squeeze; Failed to create multicast link\n");
kfree(bcbearer);
bcbearer = NULL;
kfree(bclink);
bclink = NULL;
return -ENOMEM;
}
memset(bcbearer, 0, sizeof(struct bcbearer));
INIT_LIST_HEAD(&bcbearer->bearer.cong_links);
bcbearer->bearer.media = &bcbearer->media;
bcbearer->media.send_msg = bcbearer_send;
sprintf(bcbearer->media.name, "tipc-multicast");
bcl = &bclink->link;
memset(bclink, 0, sizeof(struct bclink));
INIT_LIST_HEAD(&bcl->waiting_ports);
bcl->next_out_no = 1;
bclink->node.lock = SPIN_LOCK_UNLOCKED;
bcl->owner = &bclink->node;
bcl->max_pkt = MAX_PKT_DEFAULT_MCAST;
link_set_queue_limits(bcl, BCLINK_WIN_DEFAULT);
bcl->b_ptr = &bcbearer->bearer;
bcl->state = WORKING_WORKING;
sprintf(bcl->name, bc_link_name);
if (BCLINK_LOG_BUF_SIZE) {
char *pb = kmalloc(BCLINK_LOG_BUF_SIZE, GFP_ATOMIC);
if (!pb)
goto nomem;
printbuf_init(&bcl->print_buf, pb, BCLINK_LOG_BUF_SIZE);
}
return TIPC_OK;
}
void bclink_stop(void)
{
spin_lock_bh(&bc_lock);
if (bcbearer) {
link_stop(bcl);
if (BCLINK_LOG_BUF_SIZE)
kfree(bcl->print_buf.buf);
bcl = NULL;
kfree(bclink);
bclink = NULL;
kfree(bcbearer);
bcbearer = NULL;
}
spin_unlock_bh(&bc_lock);
}