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c61dd61dec
In our ongoing effort to simplify the TIPC locking structure, we see a need to remove the linked list for tipc_links in the bearer. This can be explained as follows. Currently, we have three different ways to access a link, via three different lists/tables: 1: Via a node hash table: Used by the time-critical outgoing/incoming data paths. (e.g. link_send_sections_fast() and tipc_recv_msg() ): grab net_lock(read) find node from node hash table grab node_lock select link grab bearer_lock send_msg() release bearer_lock release node lock release net_lock 2: Via a global linked list for nodes: Used by configuration commands (link_cmd_set_value()) grab net_lock(read) find node and link from global node list (using link name) grab node_lock update link release node lock release net_lock (Same locking order as above. No problem.) 3: Via the bearer's linked link list: Used by notifications from interface (e.g. tipc_disable_bearer() ) grab net_lock(write) grab bearer_lock get link ptr from bearer's link list get node from link grab node_lock delete link release node lock release bearer_lock release net_lock (Different order from above, but works because we grab the outer net_lock in write mode first, excluding all other access.) The first major goal in our simplification effort is to get rid of the "big" net_lock, replacing it with rcu-locks when accessing the node list and node hash array. This will come in a later patch series. But to get there we first need to rewrite access methods ##2 and 3, since removal of net_lock would introduce three major problems: a) In access method #2, we access the link before taking the protecting node_lock. This will not work once net_lock is gone, so we will have to change the access order. We will deal with this in a later commit in this series, "tipc: add node lock protection to link found by link_find_link()". b) When the outer protection from net_lock is gone, taking bearer_lock and node_lock in opposite order of method 1) and 2) will become an obvious deadlock hazard. This is fixed in the commit ("tipc: remove bearer_lock from tipc_bearer struct") later in this series. c) Similar to what is described in problem a), access method #3 starts with using a link pointer that is unprotected by node_lock, in order to via that pointer find the correct node struct and lock it. Before we remove net_lock, this access order must be altered. This is what we do with this commit. We can avoid introducing problem problem c) by even here using the global node list to find the node, before accessing its links. When we loop though the node list we use the own bearer identity as search criteria, thus easily finding the links that are associated to the resetting/disabling bearer. It should be noted that although this method is somewhat slower than the current list traversal, it is in no way time critical. This is only about resetting or deleting links, something that must be considered relatively infrequent events. As a bonus, we can get rid of the mutual pointers between links and bearers. After this commit, pointer dependency go in one direction only: from the link to the bearer. This commit pre-empts introduction of problem c) as described above. Signed-off-by: Ying Xue <ying.xue@windriver.com> Reviewed-by: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Signed-off-by: David S. Miller <davem@davemloft.net>
189 lines
5.0 KiB
C
189 lines
5.0 KiB
C
/*
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* net/tipc/core.c: TIPC module code
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*
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* Copyright (c) 2003-2006, 2013, Ericsson AB
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* Copyright (c) 2005-2006, 2010-2013, Wind River Systems
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the names of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* Alternatively, this software may be distributed under the terms of the
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* GNU General Public License ("GPL") version 2 as published by the Free
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* Software Foundation.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "core.h"
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#include "ref.h"
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#include "name_table.h"
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#include "subscr.h"
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#include "config.h"
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#include "port.h"
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#include <linux/module.h>
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/* global variables used by multiple sub-systems within TIPC */
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int tipc_random __read_mostly;
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/* configurable TIPC parameters */
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u32 tipc_own_addr __read_mostly;
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int tipc_max_ports __read_mostly;
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int tipc_net_id __read_mostly;
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int tipc_remote_management __read_mostly;
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int sysctl_tipc_rmem[3] __read_mostly; /* min/default/max */
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/**
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* tipc_buf_acquire - creates a TIPC message buffer
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* @size: message size (including TIPC header)
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*
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* Returns a new buffer with data pointers set to the specified size.
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*
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* NOTE: Headroom is reserved to allow prepending of a data link header.
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* There may also be unrequested tailroom present at the buffer's end.
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*/
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struct sk_buff *tipc_buf_acquire(u32 size)
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{
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struct sk_buff *skb;
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unsigned int buf_size = (BUF_HEADROOM + size + 3) & ~3u;
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skb = alloc_skb_fclone(buf_size, GFP_ATOMIC);
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if (skb) {
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skb_reserve(skb, BUF_HEADROOM);
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skb_put(skb, size);
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skb->next = NULL;
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}
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return skb;
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}
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/**
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* tipc_core_stop_net - shut down TIPC networking sub-systems
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*/
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static void tipc_core_stop_net(void)
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{
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tipc_net_stop();
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tipc_bearer_cleanup();
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}
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/**
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* start_net - start TIPC networking sub-systems
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*/
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int tipc_core_start_net(unsigned long addr)
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{
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int res;
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tipc_net_start(addr);
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res = tipc_bearer_setup();
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if (res < 0)
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goto err;
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return res;
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err:
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tipc_core_stop_net();
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return res;
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}
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/**
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* tipc_core_stop - switch TIPC from SINGLE NODE to NOT RUNNING mode
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*/
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static void tipc_core_stop(void)
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{
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tipc_netlink_stop();
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tipc_cfg_stop();
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tipc_subscr_stop();
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tipc_nametbl_stop();
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tipc_ref_table_stop();
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tipc_socket_stop();
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tipc_unregister_sysctl();
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}
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/**
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* tipc_core_start - switch TIPC from NOT RUNNING to SINGLE NODE mode
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*/
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static int tipc_core_start(void)
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{
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int res;
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get_random_bytes(&tipc_random, sizeof(tipc_random));
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res = tipc_handler_start();
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if (!res)
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res = tipc_ref_table_init(tipc_max_ports, tipc_random);
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if (!res)
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res = tipc_nametbl_init();
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if (!res)
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res = tipc_netlink_start();
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if (!res)
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res = tipc_socket_init();
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if (!res)
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res = tipc_register_sysctl();
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if (!res)
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res = tipc_subscr_start();
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if (!res)
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res = tipc_cfg_init();
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if (res) {
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tipc_handler_stop();
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tipc_core_stop();
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}
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return res;
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}
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static int __init tipc_init(void)
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{
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int res;
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pr_info("Activated (version " TIPC_MOD_VER ")\n");
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tipc_own_addr = 0;
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tipc_remote_management = 1;
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tipc_max_ports = CONFIG_TIPC_PORTS;
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tipc_net_id = 4711;
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sysctl_tipc_rmem[0] = CONN_OVERLOAD_LIMIT >> 4 << TIPC_LOW_IMPORTANCE;
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sysctl_tipc_rmem[1] = CONN_OVERLOAD_LIMIT >> 4 <<
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TIPC_CRITICAL_IMPORTANCE;
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sysctl_tipc_rmem[2] = CONN_OVERLOAD_LIMIT;
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res = tipc_core_start();
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if (res)
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pr_err("Unable to start in single node mode\n");
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else
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pr_info("Started in single node mode\n");
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return res;
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}
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static void __exit tipc_exit(void)
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{
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tipc_handler_stop();
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tipc_core_stop_net();
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tipc_core_stop();
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pr_info("Deactivated\n");
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}
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module_init(tipc_init);
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module_exit(tipc_exit);
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MODULE_DESCRIPTION("TIPC: Transparent Inter Process Communication");
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MODULE_LICENSE("Dual BSD/GPL");
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MODULE_VERSION(TIPC_MOD_VER);
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