gw-rwlock.c

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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 <amalysh@kannel.org>, 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 = gwlist_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 = gwlist_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
    gwlist_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
    gwlist_lock(lock->rwlock);
    gwlist_add_producer(lock->rwlock);
    gwlist_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;
        gwlist_unlock(lock->rwlock);
    } else 
        gwlist_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);
    gwlist_lock(lock->rwlock);
    RWDEBUG("", 0, "------------ gw_rwlock_wrlock(%p) producers=%d", lock, gwlist_producer_count(lock->rwlock));
    /* wait for reader */
    gwlist_consume(lock->rwlock);
    lock->writer = gwthread_self();
#endif

    return ret;
}