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authorYing Xue <ying.xue@windriver.com>2014-03-27 12:54:39 +0800
committerDavid S. Miller <davem@davemloft.net>2014-03-27 13:08:38 -0400
commitdde2026608fbf24e1687a2b62c4752022f429252 (patch)
tree829cd112db96c7c1e7fcacb9544f36703c06ac4a /net/tipc/node.c
parent2220646a53aa588798653232e26172ec36ab06cd (diff)
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tipc: use node list lock to protect tipc_num_links variable
Without properly implicit or explicit read memory barrier, it's unsafe to read an atomic variable with atomic_read() from another thread which is different with the thread of changing the atomic variable with atomic_inc() or atomic_dec(). So a stale tipc_num_links may be got with atomic_read() in tipc_node_get_links(). If the tipc_num_links variable type is converted from atomic to unsigned integer and node list lock is used to protect it, the issue would be avoided. Signed-off-by: Ying Xue <ying.xue@windriver.com> Reviewed-by: Erik Hugne <erik.hugne@ericsson.com> Reviewed-by: Jon Maloy <jon.maloy@ericsson.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/tipc/node.c')
-rw-r--r--net/tipc/node.c21
1 files changed, 11 insertions, 10 deletions
diff --git a/net/tipc/node.c b/net/tipc/node.c
index 85405a6e3076..1d3a4999a70f 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -47,10 +47,9 @@ static void node_established_contact(struct tipc_node *n_ptr);
static struct hlist_head node_htable[NODE_HTABLE_SIZE];
LIST_HEAD(tipc_node_list);
static u32 tipc_num_nodes;
+static u32 tipc_num_links;
static DEFINE_SPINLOCK(node_list_lock);
-static atomic_t tipc_num_links = ATOMIC_INIT(0);
-
/*
* A trivial power-of-two bitmask technique is used for speed, since this
* operation is done for every incoming TIPC packet. The number of hash table
@@ -241,7 +240,9 @@ int tipc_node_is_up(struct tipc_node *n_ptr)
void tipc_node_attach_link(struct tipc_node *n_ptr, struct tipc_link *l_ptr)
{
n_ptr->links[l_ptr->b_ptr->identity] = l_ptr;
- atomic_inc(&tipc_num_links);
+ spin_lock_bh(&node_list_lock);
+ tipc_num_links++;
+ spin_unlock_bh(&node_list_lock);
n_ptr->link_cnt++;
}
@@ -253,7 +254,9 @@ void tipc_node_detach_link(struct tipc_node *n_ptr, struct tipc_link *l_ptr)
if (l_ptr != n_ptr->links[i])
continue;
n_ptr->links[i] = NULL;
- atomic_dec(&tipc_num_links);
+ spin_lock_bh(&node_list_lock);
+ tipc_num_links--;
+ spin_unlock_bh(&node_list_lock);
n_ptr->link_cnt--;
}
}
@@ -393,18 +396,17 @@ struct sk_buff *tipc_node_get_links(const void *req_tlv_area, int req_tlv_space)
spin_lock_bh(&node_list_lock);
/* Get space for all unicast links + broadcast link */
- payload_size = TLV_SPACE(sizeof(link_info)) *
- (atomic_read(&tipc_num_links) + 1);
+ payload_size = TLV_SPACE((sizeof(link_info)) * (tipc_num_links + 1));
if (payload_size > 32768u) {
spin_unlock_bh(&node_list_lock);
return tipc_cfg_reply_error_string(TIPC_CFG_NOT_SUPPORTED
" (too many links)");
}
+ spin_unlock_bh(&node_list_lock);
+
buf = tipc_cfg_reply_alloc(payload_size);
- if (!buf) {
- spin_unlock_bh(&node_list_lock);
+ if (!buf)
return NULL;
- }
/* Add TLV for broadcast link */
link_info.dest = htonl(tipc_cluster_mask(tipc_own_addr));
@@ -432,6 +434,5 @@ struct sk_buff *tipc_node_get_links(const void *req_tlv_area, int req_tlv_space)
tipc_node_unlock(n_ptr);
}
rcu_read_unlock();
- spin_unlock_bh(&node_list_lock);
return buf;
}