mirror of https://gitee.com/openkylin/linux.git
140 lines
2.7 KiB
C
140 lines
2.7 KiB
C
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/*
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* net/dccp/ccid.c
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*
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* An implementation of the DCCP protocol
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* Arnaldo Carvalho de Melo <acme@conectiva.com.br>
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*
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* CCID infrastructure
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include "ccid.h"
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static struct ccid *ccids[CCID_MAX];
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#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
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static atomic_t ccids_lockct = ATOMIC_INIT(0);
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static DEFINE_SPINLOCK(ccids_lock);
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/*
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* The strategy is: modifications ccids vector are short, do not sleep and
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* veeery rare, but read access should be free of any exclusive locks.
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*/
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static void ccids_write_lock(void)
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{
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spin_lock(&ccids_lock);
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while (atomic_read(&ccids_lockct) != 0) {
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spin_unlock(&ccids_lock);
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yield();
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spin_lock(&ccids_lock);
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}
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}
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static inline void ccids_write_unlock(void)
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{
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spin_unlock(&ccids_lock);
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}
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static inline void ccids_read_lock(void)
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{
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atomic_inc(&ccids_lockct);
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spin_unlock_wait(&ccids_lock);
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}
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static inline void ccids_read_unlock(void)
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{
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atomic_dec(&ccids_lockct);
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}
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#else
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#define ccids_write_lock() do { } while(0)
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#define ccids_write_unlock() do { } while(0)
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#define ccids_read_lock() do { } while(0)
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#define ccids_read_unlock() do { } while(0)
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#endif
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int ccid_register(struct ccid *ccid)
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{
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int err;
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if (ccid->ccid_init == NULL)
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return -1;
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ccids_write_lock();
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err = -EEXIST;
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if (ccids[ccid->ccid_id] == NULL) {
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ccids[ccid->ccid_id] = ccid;
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err = 0;
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}
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ccids_write_unlock();
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if (err == 0)
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pr_info("CCID: Registered CCID %d (%s)\n",
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ccid->ccid_id, ccid->ccid_name);
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return err;
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}
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EXPORT_SYMBOL_GPL(ccid_register);
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int ccid_unregister(struct ccid *ccid)
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{
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ccids_write_lock();
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ccids[ccid->ccid_id] = NULL;
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ccids_write_unlock();
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pr_info("CCID: Unregistered CCID %d (%s)\n",
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ccid->ccid_id, ccid->ccid_name);
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return 0;
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}
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EXPORT_SYMBOL_GPL(ccid_unregister);
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struct ccid *ccid_init(unsigned char id, struct sock *sk)
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{
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struct ccid *ccid;
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#ifdef CONFIG_KMOD
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if (ccids[id] == NULL)
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request_module("net-dccp-ccid-%d", id);
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#endif
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ccids_read_lock();
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ccid = ccids[id];
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if (ccid == NULL)
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goto out;
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if (!try_module_get(ccid->ccid_owner))
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goto out_err;
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if (ccid->ccid_init(sk) != 0)
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goto out_module_put;
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out:
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ccids_read_unlock();
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return ccid;
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out_module_put:
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module_put(ccid->ccid_owner);
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out_err:
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ccid = NULL;
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goto out;
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}
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EXPORT_SYMBOL_GPL(ccid_init);
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void ccid_exit(struct ccid *ccid, struct sock *sk)
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{
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if (ccid == NULL)
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return;
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ccids_read_lock();
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if (ccids[ccid->ccid_id] != NULL) {
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if (ccid->ccid_exit != NULL)
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ccid->ccid_exit(sk);
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module_put(ccid->ccid_owner);
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}
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ccids_read_unlock();
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}
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EXPORT_SYMBOL_GPL(ccid_exit);
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