Arnaldo Carvalho de Melo | 7c65787 | 2005-08-09 20:14:34 -0700 | [diff] [blame] | 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 | |
| 16 | static struct ccid *ccids[CCID_MAX]; |
| 17 | #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT) |
| 18 | static atomic_t ccids_lockct = ATOMIC_INIT(0); |
| 19 | static 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 | */ |
| 25 | static 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 | |
| 35 | static inline void ccids_write_unlock(void) |
| 36 | { |
| 37 | spin_unlock(&ccids_lock); |
| 38 | } |
| 39 | |
| 40 | static inline void ccids_read_lock(void) |
| 41 | { |
| 42 | atomic_inc(&ccids_lockct); |
| 43 | spin_unlock_wait(&ccids_lock); |
| 44 | } |
| 45 | |
| 46 | static 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 | |
| 58 | int ccid_register(struct ccid *ccid) |
| 59 | { |
| 60 | int err; |
| 61 | |
Arnaldo Carvalho de Melo | 7c65787 | 2005-08-09 20:14:34 -0700 | [diff] [blame] | 62 | ccids_write_lock(); |
| 63 | err = -EEXIST; |
| 64 | if (ccids[ccid->ccid_id] == NULL) { |
| 65 | ccids[ccid->ccid_id] = ccid; |
| 66 | err = 0; |
| 67 | } |
| 68 | ccids_write_unlock(); |
| 69 | if (err == 0) |
| 70 | pr_info("CCID: Registered CCID %d (%s)\n", |
| 71 | ccid->ccid_id, ccid->ccid_name); |
| 72 | return err; |
| 73 | } |
| 74 | |
| 75 | EXPORT_SYMBOL_GPL(ccid_register); |
| 76 | |
| 77 | int ccid_unregister(struct ccid *ccid) |
| 78 | { |
| 79 | ccids_write_lock(); |
| 80 | ccids[ccid->ccid_id] = NULL; |
| 81 | ccids_write_unlock(); |
| 82 | pr_info("CCID: Unregistered CCID %d (%s)\n", |
| 83 | ccid->ccid_id, ccid->ccid_name); |
| 84 | return 0; |
| 85 | } |
| 86 | |
| 87 | EXPORT_SYMBOL_GPL(ccid_unregister); |
| 88 | |
| 89 | struct ccid *ccid_init(unsigned char id, struct sock *sk) |
| 90 | { |
| 91 | struct ccid *ccid; |
| 92 | |
| 93 | #ifdef CONFIG_KMOD |
| 94 | if (ccids[id] == NULL) |
| 95 | request_module("net-dccp-ccid-%d", id); |
| 96 | #endif |
| 97 | ccids_read_lock(); |
| 98 | |
| 99 | ccid = ccids[id]; |
| 100 | if (ccid == NULL) |
| 101 | goto out; |
| 102 | |
| 103 | if (!try_module_get(ccid->ccid_owner)) |
| 104 | goto out_err; |
| 105 | |
Arnaldo Carvalho de Melo | 4114470 | 2006-03-20 17:20:23 -0800 | [diff] [blame] | 106 | if (ccid->ccid_init != NULL && ccid->ccid_init(sk) != 0) |
Arnaldo Carvalho de Melo | 7c65787 | 2005-08-09 20:14:34 -0700 | [diff] [blame] | 107 | goto out_module_put; |
| 108 | out: |
| 109 | ccids_read_unlock(); |
| 110 | return ccid; |
| 111 | out_module_put: |
| 112 | module_put(ccid->ccid_owner); |
| 113 | out_err: |
| 114 | ccid = NULL; |
| 115 | goto out; |
| 116 | } |
| 117 | |
| 118 | EXPORT_SYMBOL_GPL(ccid_init); |
| 119 | |
| 120 | void ccid_exit(struct ccid *ccid, struct sock *sk) |
| 121 | { |
| 122 | if (ccid == NULL) |
| 123 | return; |
| 124 | |
| 125 | ccids_read_lock(); |
| 126 | |
| 127 | if (ccids[ccid->ccid_id] != NULL) { |
| 128 | if (ccid->ccid_exit != NULL) |
| 129 | ccid->ccid_exit(sk); |
| 130 | module_put(ccid->ccid_owner); |
| 131 | } |
| 132 | |
| 133 | ccids_read_unlock(); |
| 134 | } |
| 135 | |
| 136 | EXPORT_SYMBOL_GPL(ccid_exit); |