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[tipc-discussion] [PATCH net-next v3 01/12] tipc: convert 'blocked' flag in struct tipc_bearer to atomic_t
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From: Ying X. <yin...@wi...> - 2013-09-30 08:38:44
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The 'blocked' flag in struct tipc_bearer is currently protected by
a big spinlock aggregated into tipc_bearer. We want to reduce all
dependencies to this lock, as part of our effort to make the locking
policy simpler and more manageable.
Furthermore, the functions tipc_disc_recv_msg() and disc_send_msg()
access the flag without taking this lock at all, implying a risk that
they may occasionally obtain a wrong value and drop sending/receiving
of discovery messages. Since discovery messages are timer driven and
best-effort, the latter problem is not fatal, but it is clearly avoidable.
By converting the type of the flag from int to atomic_t we eliminate
both the spinlock dependency and the current race condition.
We also make two small code changes:
1) The functions tipc_continue() and bearer_blocked() now become
one-liners doing a single access to the flag. So we just remove
those redundant functions.
2) The initialization of the flag is moved from the enable_media()
functions in ib_media.c and eth_media.c respecively, to the generic
tipc_enable_bearer() function, so that it is done in one place only.
Signed-off-by: Ying Xue <yin...@wi...>
---
net/tipc/bcast.c | 4 ++--
net/tipc/bearer.c | 33 ++++-----------------------------
net/tipc/bearer.h | 5 +----
net/tipc/discover.c | 5 +++--
net/tipc/eth_media.c | 9 ++++-----
net/tipc/ib_media.c | 9 ++++-----
net/tipc/link.c | 12 ++++++------
7 files changed, 24 insertions(+), 53 deletions(-)
diff --git a/net/tipc/bcast.c b/net/tipc/bcast.c
index 716de1a..c78f30c 100644
--- a/net/tipc/bcast.c
+++ b/net/tipc/bcast.c
@@ -615,8 +615,8 @@ static int tipc_bcbearer_send(struct sk_buff *buf, struct tipc_bearer *unused1,
if (!p)
break; /* No more bearers to try */
- if (tipc_bearer_blocked(p)) {
- if (!s || tipc_bearer_blocked(s))
+ if (atomic_read(&p->blocked)) {
+ if (!s || atomic_read(&s->blocked))
continue; /* Can't use either bearer */
b = s;
}
diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
index 3f9707a..17f9824 100644
--- a/net/tipc/bearer.c
+++ b/net/tipc/bearer.c
@@ -275,31 +275,6 @@ void tipc_bearer_remove_dest(struct tipc_bearer *b_ptr, u32 dest)
tipc_disc_remove_dest(b_ptr->link_req);
}
-/*
- * Interrupt enabling new requests after bearer blocking:
- * See bearer_send().
- */
-void tipc_continue(struct tipc_bearer *b)
-{
- spin_lock_bh(&b->lock);
- b->blocked = 0;
- spin_unlock_bh(&b->lock);
-}
-
-/*
- * tipc_bearer_blocked - determines if bearer is currently blocked
- */
-int tipc_bearer_blocked(struct tipc_bearer *b)
-{
- int res;
-
- spin_lock_bh(&b->lock);
- res = b->blocked;
- spin_unlock_bh(&b->lock);
-
- return res;
-}
-
/**
* tipc_enable_bearer - enable bearer with the given name
*/
@@ -387,6 +362,8 @@ restart:
b_ptr = &tipc_bearers[bearer_id];
strcpy(b_ptr->name, name);
+ atomic_set(&b_ptr->blocked, 0);
+ smp_mb();
res = m_ptr->enable_media(b_ptr);
if (res) {
pr_warn("Bearer <%s> rejected, enable failure (%d)\n",
@@ -429,8 +406,8 @@ int tipc_block_bearer(struct tipc_bearer *b_ptr)
read_lock_bh(&tipc_net_lock);
pr_info("Blocking bearer <%s>\n", b_ptr->name);
+ atomic_add_unless(&b_ptr->blocked, 1, 1);
spin_lock_bh(&b_ptr->lock);
- b_ptr->blocked = 1;
list_for_each_entry_safe(l_ptr, temp_l_ptr, &b_ptr->links, link_list) {
struct tipc_node *n_ptr = l_ptr->owner;
@@ -455,8 +432,8 @@ static void bearer_disable(struct tipc_bearer *b_ptr)
struct tipc_link_req *temp_req;
pr_info("Disabling bearer <%s>\n", b_ptr->name);
+ atomic_add_unless(&b_ptr->blocked, 1, 1);
spin_lock_bh(&b_ptr->lock);
- b_ptr->blocked = 1;
b_ptr->media->disable_media(b_ptr);
list_for_each_entry_safe(l_ptr, temp_l_ptr, &b_ptr->links, link_list) {
tipc_link_delete(l_ptr);
@@ -489,8 +466,6 @@ int tipc_disable_bearer(const char *name)
return res;
}
-
-
void tipc_bearer_stop(void)
{
u32 i;
diff --git a/net/tipc/bearer.h b/net/tipc/bearer.h
index e5e04be..8695d4a 100644
--- a/net/tipc/bearer.h
+++ b/net/tipc/bearer.h
@@ -130,7 +130,7 @@ struct tipc_media {
struct tipc_bearer {
void *usr_handle; /* initalized by media */
u32 mtu; /* initalized by media */
- int blocked; /* initalized by media */
+ atomic_t blocked;
struct tipc_media_addr addr; /* initalized by media */
char name[TIPC_MAX_BEARER_NAME];
spinlock_t lock;
@@ -164,8 +164,6 @@ int tipc_register_media(struct tipc_media *m_ptr);
void tipc_recv_msg(struct sk_buff *buf, struct tipc_bearer *tb_ptr);
int tipc_block_bearer(struct tipc_bearer *b_ptr);
-void tipc_continue(struct tipc_bearer *tb_ptr);
-
int tipc_enable_bearer(const char *bearer_name, u32 disc_domain, u32 priority);
int tipc_disable_bearer(const char *name);
@@ -194,7 +192,6 @@ void tipc_bearer_remove_dest(struct tipc_bearer *b_ptr, u32 dest);
struct tipc_bearer *tipc_bearer_find(const char *name);
struct tipc_bearer *tipc_bearer_find_interface(const char *if_name);
struct tipc_media *tipc_media_find(const char *name);
-int tipc_bearer_blocked(struct tipc_bearer *b_ptr);
void tipc_bearer_stop(void);
/**
diff --git a/net/tipc/discover.c b/net/tipc/discover.c
index ecc758c..d8b49fb 100644
--- a/net/tipc/discover.c
+++ b/net/tipc/discover.c
@@ -239,7 +239,8 @@ void tipc_disc_recv_msg(struct sk_buff *buf, struct tipc_bearer *b_ptr)
/* Accept discovery message & send response, if necessary */
link_fully_up = link_working_working(link);
- if ((type == DSC_REQ_MSG) && !link_fully_up && !b_ptr->blocked) {
+ if ((type == DSC_REQ_MSG) && !link_fully_up &&
+ !atomic_read(&b_ptr->blocked)) {
rbuf = tipc_disc_init_msg(DSC_RESP_MSG, orig, b_ptr);
if (rbuf) {
tipc_bearer_send(b_ptr, rbuf, &media_addr);
@@ -293,7 +294,7 @@ void tipc_disc_remove_dest(struct tipc_link_req *req)
*/
static void disc_send_msg(struct tipc_link_req *req)
{
- if (!req->bearer->blocked)
+ if (!atomic_read(&req->bearer->blocked))
tipc_bearer_send(req->bearer, req->buf, &req->dest);
}
diff --git a/net/tipc/eth_media.c b/net/tipc/eth_media.c
index f80d59f..32d01e8 100644
--- a/net/tipc/eth_media.c
+++ b/net/tipc/eth_media.c
@@ -1,7 +1,7 @@
/*
* net/tipc/eth_media.c: Ethernet bearer support for TIPC
*
- * Copyright (c) 2001-2007, Ericsson AB
+ * Copyright (c) 2001-2007, 2013, Ericsson AB
* Copyright (c) 2005-2008, 2011-2013, Wind River Systems
* All rights reserved.
*
@@ -199,7 +199,6 @@ static int enable_media(struct tipc_bearer *tb_ptr)
tb_ptr->bcast_addr.media_id = TIPC_MEDIA_TYPE_ETH;
tb_ptr->bcast_addr.broadcast = 1;
tb_ptr->mtu = dev->mtu;
- tb_ptr->blocked = 0;
eth_media_addr_set(tb_ptr, &tb_ptr->addr, (char *)dev->dev_addr);
return 0;
}
@@ -263,12 +262,12 @@ static int recv_notification(struct notifier_block *nb, unsigned long evt,
switch (evt) {
case NETDEV_CHANGE:
if (netif_carrier_ok(dev))
- tipc_continue(eb_ptr->bearer);
+ atomic_add_unless(&eb_ptr->bearer->blocked, -1, 0);
else
tipc_block_bearer(eb_ptr->bearer);
break;
case NETDEV_UP:
- tipc_continue(eb_ptr->bearer);
+ atomic_add_unless(&eb_ptr->bearer->blocked, -1, 0);
break;
case NETDEV_DOWN:
tipc_block_bearer(eb_ptr->bearer);
@@ -276,7 +275,7 @@ static int recv_notification(struct notifier_block *nb, unsigned long evt,
case NETDEV_CHANGEMTU:
case NETDEV_CHANGEADDR:
tipc_block_bearer(eb_ptr->bearer);
- tipc_continue(eb_ptr->bearer);
+ atomic_add_unless(&eb_ptr->bearer->blocked, -1, 0);
break;
case NETDEV_UNREGISTER:
case NETDEV_CHANGENAME:
diff --git a/net/tipc/ib_media.c b/net/tipc/ib_media.c
index c139892..5241a5b 100644
--- a/net/tipc/ib_media.c
+++ b/net/tipc/ib_media.c
@@ -5,7 +5,7 @@
*
* Based on eth_media.c, which carries the following copyright notice:
*
- * Copyright (c) 2001-2007, Ericsson AB
+ * Copyright (c) 2001-2007, 2013, Ericsson AB
* Copyright (c) 2005-2008, 2011, Wind River Systems
* All rights reserved.
*
@@ -192,7 +192,6 @@ static int enable_media(struct tipc_bearer *tb_ptr)
tb_ptr->bcast_addr.media_id = TIPC_MEDIA_TYPE_IB;
tb_ptr->bcast_addr.broadcast = 1;
tb_ptr->mtu = dev->mtu;
- tb_ptr->blocked = 0;
ib_media_addr_set(tb_ptr, &tb_ptr->addr, (char *)dev->dev_addr);
return 0;
}
@@ -256,12 +255,12 @@ static int recv_notification(struct notifier_block *nb, unsigned long evt,
switch (evt) {
case NETDEV_CHANGE:
if (netif_carrier_ok(dev))
- tipc_continue(ib_ptr->bearer);
+ atomic_add_unless(&ib_ptr->bearer->blocked, -1, 0);
else
tipc_block_bearer(ib_ptr->bearer);
break;
case NETDEV_UP:
- tipc_continue(ib_ptr->bearer);
+ atomic_add_unless(&ib_ptr->bearer->blocked, -1, 0);
break;
case NETDEV_DOWN:
tipc_block_bearer(ib_ptr->bearer);
@@ -269,7 +268,7 @@ static int recv_notification(struct notifier_block *nb, unsigned long evt,
case NETDEV_CHANGEMTU:
case NETDEV_CHANGEADDR:
tipc_block_bearer(ib_ptr->bearer);
- tipc_continue(ib_ptr->bearer);
+ atomic_add_unless(&ib_ptr->bearer->blocked, -1, 0);
break;
case NETDEV_UNREGISTER:
case NETDEV_CHANGENAME:
diff --git a/net/tipc/link.c b/net/tipc/link.c
index 4d1297e..8c0e9a3 100644
--- a/net/tipc/link.c
+++ b/net/tipc/link.c
@@ -796,7 +796,7 @@ int tipc_link_send_buf(struct tipc_link *l_ptr, struct sk_buff *buf)
return link_send_long_buf(l_ptr, buf);
/* Packet can be queued or sent. */
- if (likely(!tipc_bearer_blocked(l_ptr->b_ptr) &&
+ if (likely(!atomic_read(&l_ptr->b_ptr->blocked) &&
!link_congested(l_ptr))) {
link_add_to_outqueue(l_ptr, buf, msg);
@@ -963,7 +963,7 @@ static int link_send_buf_fast(struct tipc_link *l_ptr, struct sk_buff *buf,
if (likely(!link_congested(l_ptr))) {
if (likely(msg_size(msg) <= l_ptr->max_pkt)) {
- if (likely(!tipc_bearer_blocked(l_ptr->b_ptr))) {
+ if (likely(!atomic_read(&l_ptr->b_ptr->blocked))) {
link_add_to_outqueue(l_ptr, buf, msg);
tipc_bearer_send(l_ptr->b_ptr, buf,
&l_ptr->media_addr);
@@ -1020,7 +1020,7 @@ exit:
/* Exit if link (or bearer) is congested */
if (link_congested(l_ptr) ||
- tipc_bearer_blocked(l_ptr->b_ptr)) {
+ atomic_read(&l_ptr->b_ptr->blocked)) {
res = link_schedule_port(l_ptr,
sender->ref, res);
goto exit;
@@ -1287,7 +1287,7 @@ void tipc_link_push_queue(struct tipc_link *l_ptr)
{
u32 res;
- if (tipc_bearer_blocked(l_ptr->b_ptr))
+ if (atomic_read(&l_ptr->b_ptr->blocked))
return;
do {
@@ -1376,7 +1376,7 @@ void tipc_link_retransmit(struct tipc_link *l_ptr, struct sk_buff *buf,
msg = buf_msg(buf);
- if (tipc_bearer_blocked(l_ptr->b_ptr)) {
+ if (atomic_read(&l_ptr->b_ptr->blocked)) {
if (l_ptr->retransm_queue_size == 0) {
l_ptr->retransm_queue_head = msg_seqno(msg);
l_ptr->retransm_queue_size = retransmits;
@@ -1870,7 +1870,7 @@ void tipc_link_send_proto_msg(struct tipc_link *l_ptr, u32 msg_typ,
buf->priority = TC_PRIO_CONTROL;
/* Defer message if bearer is already blocked */
- if (tipc_bearer_blocked(l_ptr->b_ptr)) {
+ if (atomic_read(&l_ptr->b_ptr->blocked)) {
l_ptr->proto_msg_queue = buf;
return;
}
--
1.7.9.5
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