gw-rwlock.c

The Kannel Open Source WAP and SMS gateway works as both an SMS gateway, for implementing keyword b

/* ==================================================================== 
 * The Kannel Software License, Version 1.0 
 * 
 * Copyright (c) 2001-2004 Kannel Group  
 * Copyright (c) 1998-2001 WapIT Ltd.   
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 *    if any, must include the following acknowledgment: 
 *       "This product includes software developed by the 
 *        Kannel Group (http://www.kannel.org/)." 
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 * This software consists of voluntary contributions made by many 
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 * 
 * Portions of this software are based upon software originally written at  
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 */ 

/*
 * gw-rwlock.c: Implements Reader/Writer Lock.
 * If pthread_rwlock_XXX functions are present then those will be used;
 * otherwise emulation with mutexes/condition should be done.
 *
 * Alexander Malysh <[e-mail]>, initial version 2004
 */

#include "gw-config.h"
#include "gwlib.h"
#include "gw-rwlock.h"

#define DEBUG 0
#if DEBUG
  #define RWDEBUG(str,lev,frm,args...) debug(str, lev, frm, ## args)
#else
  #define RWDEBUG(str,lev,frm,args...) do{}while(0)
#endif


RWLock *gw_rwlock_create(void)
{
    RWLock *ret = gw_malloc(sizeof(*ret));
#ifdef HAVE_PTHREAD_RWLOCK
    int rc = pthread_rwlock_init(&ret->rwlock, NULL);
    if (rc != 0)
        panic(rc, "Initialization of RWLock failed.");
#else
    ret->writer = -1;
    ret->rwlock = list_create();
    if (ret->rwlock == NULL)
        panic(0, "Initialization of RWLock failed.");
#endif
    ret->dynamic = 1;

    return ret;
}


void gw_rwlock_init_static(RWLock *lock)
{
#ifdef HAVE_PTHREAD_RWLOCK
    int rc = pthread_rwlock_init(&lock->rwlock, NULL);
    if (rc != 0)
        panic(rc, "Initialization of RWLock failed.");
#else
    lock->writer = -1;
    lock->rwlock = list_create();
    if (lock->rwlock == NULL)
        panic(0, "Initialization of RWLock failed.");
#endif
    lock->dynamic = 0;
}


void gw_rwlock_destroy(RWLock *lock)
{
#ifdef HAVE_PTHREAD_RWLOCK
    int ret;
#endif

    if (!lock)
        return;

#ifdef HAVE_PTHREAD_RWLOCK
    ret = pthread_rwlock_destroy(&lock->rwlock);
    if (ret != 0)
        panic(ret, "Attempt to destroy locked rwlock.");
#else
    list_destroy(lock->rwlock, NULL);
#endif

    if (lock->dynamic)
        gw_free(lock);
}


int gw_rwlock_rdlock(RWLock *lock)
{
    int ret = 0;
    gw_assert(lock != NULL);

#ifdef HAVE_PTHREAD_RWLOCK
    ret = pthread_rwlock_rdlock(&lock->rwlock);
    if (ret != 0) {
        panic(ret, "Error while pthread_rwlock_rdlock.");
    }
#else
    list_lock(lock->rwlock);
    list_add_producer(lock->rwlock);
    list_unlock(lock->rwlock);
    RWDEBUG("", 0, "------------ gw_rwlock_rdlock(%p) ----------", lock);
#endif

    return ret;
}


int gw_rwlock_unlock(RWLock *lock)
{
    int ret = 0;
    gw_assert(lock != NULL);

#ifdef HAVE_PTHREAD_RWLOCK
    ret = pthread_rwlock_unlock(&lock->rwlock);
    if (ret != 0)
        panic(ret, "Error while gw_rwlock_unlock.");
#else
    RWDEBUG("", 0, "------------ gw_rwlock_unlock(%p) ----------", lock);
    if (lock->writer == gwthread_self()) {
        lock->writer = -1;
        list_unlock(lock->rwlock);
    } else 
        list_remove_producer(lock->rwlock);
#endif

    return ret;
}


int gw_rwlock_wrlock(RWLock *lock)
{
    int ret = 0;
    gw_assert(lock != NULL);

#ifdef HAVE_PTHREAD_RWLOCK
    ret = pthread_rwlock_wrlock(&lock->rwlock);
    if (ret != 0)
        panic(ret, "Error while pthread_rwlock_wrlock.");
#else
    RWDEBUG("", 0, "------------ gw_rwlock_wrlock(%p) ----------", lock);
    list_lock(lock->rwlock);
    RWDEBUG("", 0, "------------ gw_rwlock_wrlock(%p) producers=%d", lock, list_producer_count(lock->rwlock));
    /* wait for reader */
    list_consume(lock->rwlock);
    lock->writer = gwthread_self();
#endif

    return ret;
}