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