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-rw-r--r--net/tipc/socket.c48
1 files changed, 1 insertions, 47 deletions
diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index f9f5f3c3dab5..db32777ab591 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -1,7 +1,7 @@
1/* 1/*
2 * net/tipc/socket.c: TIPC socket API 2 * net/tipc/socket.c: TIPC socket API
3 * 3 *
4 * Copyright (c) 2001-2007, 2012-2015, Ericsson AB 4 * Copyright (c) 2001-2007, 2012-2016, Ericsson AB
5 * Copyright (c) 2004-2008, 2010-2013, Wind River Systems 5 * Copyright (c) 2004-2008, 2010-2013, Wind River Systems
6 * All rights reserved. 6 * All rights reserved.
7 * 7 *
@@ -129,54 +129,8 @@ static const struct proto_ops packet_ops;
129static const struct proto_ops stream_ops; 129static const struct proto_ops stream_ops;
130static const struct proto_ops msg_ops; 130static const struct proto_ops msg_ops;
131static struct proto tipc_proto; 131static struct proto tipc_proto;
132
133static const struct rhashtable_params tsk_rht_params; 132static const struct rhashtable_params tsk_rht_params;
134 133
135/*
136 * Revised TIPC socket locking policy:
137 *
138 * Most socket operations take the standard socket lock when they start
139 * and hold it until they finish (or until they need to sleep). Acquiring
140 * this lock grants the owner exclusive access to the fields of the socket
141 * data structures, with the exception of the backlog queue. A few socket
142 * operations can be done without taking the socket lock because they only
143 * read socket information that never changes during the life of the socket.
144 *
145 * Socket operations may acquire the lock for the associated TIPC port if they
146 * need to perform an operation on the port. If any routine needs to acquire
147 * both the socket lock and the port lock it must take the socket lock first
148 * to avoid the risk of deadlock.
149 *
150 * The dispatcher handling incoming messages cannot grab the socket lock in
151 * the standard fashion, since invoked it runs at the BH level and cannot block.
152 * Instead, it checks to see if the socket lock is currently owned by someone,
153 * and either handles the message itself or adds it to the socket's backlog
154 * queue; in the latter case the queued message is processed once the process
155 * owning the socket lock releases it.
156 *
157 * NOTE: Releasing the socket lock while an operation is sleeping overcomes
158 * the problem of a blocked socket operation preventing any other operations
159 * from occurring. However, applications must be careful if they have
160 * multiple threads trying to send (or receive) on the same socket, as these
161 * operations might interfere with each other. For example, doing a connect
162 * and a receive at the same time might allow the receive to consume the
163 * ACK message meant for the connect. While additional work could be done
164 * to try and overcome this, it doesn't seem to be worthwhile at the present.
165 *
166 * NOTE: Releasing the socket lock while an operation is sleeping also ensures
167 * that another operation that must be performed in a non-blocking manner is
168 * not delayed for very long because the lock has already been taken.
169 *
170 * NOTE: This code assumes that certain fields of a port/socket pair are
171 * constant over its lifetime; such fields can be examined without taking
172 * the socket lock and/or port lock, and do not need to be re-read even
173 * after resuming processing after waiting. These fields include:
174 * - socket type
175 * - pointer to socket sk structure (aka tipc_sock structure)
176 * - pointer to port structure
177 * - port reference
178 */
179
180static u32 tsk_own_node(struct tipc_sock *tsk) 134static u32 tsk_own_node(struct tipc_sock *tsk)
181{ 135{
182 return msg_prevnode(&tsk->phdr); 136 return msg_prevnode(&tsk->phdr);