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Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 * net/dccp/ccid.c
3 *
4 * An implementation of the DCCP protocol
5 * Arnaldo Carvalho de Melo <acme@conectiva.com.br>
6 *
7 * CCID infrastructure
8 *
9 * This program is free software; you can redistribute it and/or modify it
10 * under the terms of the GNU General Public License version 2 as
11 * published by the Free Software Foundation.
12 */
13
14#include "ccid.h"
15
16static struct ccid *ccids[CCID_MAX];
17#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
18static atomic_t ccids_lockct = ATOMIC_INIT(0);
19static DEFINE_SPINLOCK(ccids_lock);
20
21/*
22 * The strategy is: modifications ccids vector are short, do not sleep and
23 * veeery rare, but read access should be free of any exclusive locks.
24 */
25static void ccids_write_lock(void)
26{
27 spin_lock(&ccids_lock);
28 while (atomic_read(&ccids_lockct) != 0) {
29 spin_unlock(&ccids_lock);
30 yield();
31 spin_lock(&ccids_lock);
32 }
33}
34
35static inline void ccids_write_unlock(void)
36{
37 spin_unlock(&ccids_lock);
38}
39
40static inline void ccids_read_lock(void)
41{
42 atomic_inc(&ccids_lockct);
43 spin_unlock_wait(&ccids_lock);
44}
45
46static inline void ccids_read_unlock(void)
47{
48 atomic_dec(&ccids_lockct);
49}
50
51#else
52#define ccids_write_lock() do { } while(0)
53#define ccids_write_unlock() do { } while(0)
54#define ccids_read_lock() do { } while(0)
55#define ccids_read_unlock() do { } while(0)
56#endif
57
58int ccid_register(struct ccid *ccid)
59{
60 int err;
61
62 if (ccid->ccid_init == NULL)
63 return -1;
64
65 ccids_write_lock();
66 err = -EEXIST;
67 if (ccids[ccid->ccid_id] == NULL) {
68 ccids[ccid->ccid_id] = ccid;
69 err = 0;
70 }
71 ccids_write_unlock();
72 if (err == 0)
73 pr_info("CCID: Registered CCID %d (%s)\n",
74 ccid->ccid_id, ccid->ccid_name);
75 return err;
76}
77
78EXPORT_SYMBOL_GPL(ccid_register);
79
80int ccid_unregister(struct ccid *ccid)
81{
82 ccids_write_lock();
83 ccids[ccid->ccid_id] = NULL;
84 ccids_write_unlock();
85 pr_info("CCID: Unregistered CCID %d (%s)\n",
86 ccid->ccid_id, ccid->ccid_name);
87 return 0;
88}
89
90EXPORT_SYMBOL_GPL(ccid_unregister);
91
92struct ccid *ccid_init(unsigned char id, struct sock *sk)
93{
94 struct ccid *ccid;
95
96#ifdef CONFIG_KMOD
97 if (ccids[id] == NULL)
98 request_module("net-dccp-ccid-%d", id);
99#endif
100 ccids_read_lock();
101
102 ccid = ccids[id];
103 if (ccid == NULL)
104 goto out;
105
106 if (!try_module_get(ccid->ccid_owner))
107 goto out_err;
108
109 if (ccid->ccid_init(sk) != 0)
110 goto out_module_put;
111out:
112 ccids_read_unlock();
113 return ccid;
114out_module_put:
115 module_put(ccid->ccid_owner);
116out_err:
117 ccid = NULL;
118 goto out;
119}
120
121EXPORT_SYMBOL_GPL(ccid_init);
122
123void ccid_exit(struct ccid *ccid, struct sock *sk)
124{
125 if (ccid == NULL)
126 return;
127
128 ccids_read_lock();
129
130 if (ccids[ccid->ccid_id] != NULL) {
131 if (ccid->ccid_exit != NULL)
132 ccid->ccid_exit(sk);
133 module_put(ccid->ccid_owner);
134 }
135
136 ccids_read_unlock();
137}
138
139EXPORT_SYMBOL_GPL(ccid_exit);