+typedef struct ldap_lazy_sem_t {
+ ldap_pvt_thread_mutex_t ls_mutex;
+ ldap_pvt_thread_cond_t ls_cond;
+ int ls_sem_value;
+ /*
+ * when more than ls_lazy_count number of resources
+ * becmoes available, the thread wating for the resources will
+ * be waken up in order to prevent frequent blocking/waking-up
+ */
+ unsigned int ls_lazy_count;
+ /*
+ * only one thread(listener) will wait on this semaphore
+ * using a flag instead of a list
+ */
+ int ls_wait;
+} ldap_lazy_sem_t;
+
+ldap_lazy_sem_t* thread_pool_sem = NULL;
+
+int
+ldap_lazy_sem_init( unsigned int value, unsigned int lazyness )
+{
+ thread_pool_sem = (ldap_lazy_sem_t*) LDAP_CALLOC(1,
+ sizeof( ldap_lazy_sem_t ));
+
+ if( thread_pool_sem == NULL ) return -1;
+
+ ldap_pvt_thread_mutex_init( &thread_pool_sem->ls_mutex );
+ ldap_pvt_thread_cond_init( &thread_pool_sem->ls_cond );
+ thread_pool_sem->ls_sem_value = value;
+ thread_pool_sem->ls_lazy_count = lazyness;
+ thread_pool_sem->ls_wait = 0;
+
+ return 0;
+}
+
+/* FIXME: move to some approprite header */
+int ldap_lazy_sem_dec( ldap_lazy_sem_t* ls );
+int ldap_lazy_sem_wait ( ldap_lazy_sem_t* ls );
+
+/*
+ * ldap_lazy_sem_wait is used if a caller is blockable(listener).
+ * Otherwise use ldap_lazy_sem_dec (worker)
+ */
+int
+ldap_lazy_sem_op_submit( ldap_lazy_sem_t* ls )
+{
+ if ( ls == NULL ) return -1;
+
+ /* only worker thread has its thread ctx */
+ if ( ldap_pvt_thread_pool_context() ) {
+ /* worker thread */
+ return ldap_lazy_sem_dec( ls );
+ } else {
+ /* listener */
+ return ldap_lazy_sem_wait( ls );
+ }
+}
+
+/*
+ * test if given semaphore's count is zero.
+ * If 0, the caller is blocked
+ * If not, the count is decremented.
+ */
+int
+ldap_lazy_sem_wait ( ldap_lazy_sem_t* ls )
+{
+ ldap_pvt_thread_mutex_lock( &ls->ls_mutex );
+
+lazy_sem_retry:
+ if ( ls->ls_sem_value <= 0 ) {
+ /* no more avaliable resources */
+ ls->ls_wait = 1;
+ ldap_pvt_thread_cond_wait( &ls->ls_cond, &ls->ls_mutex );
+ goto lazy_sem_retry;
+ } else {
+ /* avaliable resources */
+ ls->ls_sem_value--;
+ }
+
+ ldap_pvt_thread_mutex_unlock( &ls->ls_mutex );
+
+ return 0;
+}
+
+/*
+ * decrement the count without blocking
+ * even when the count becomes less than or equal to 0
+ */
+int
+ldap_lazy_sem_dec( ldap_lazy_sem_t* ls )
+{
+ ldap_pvt_thread_mutex_lock( &ls->ls_mutex );
+
+ ls->ls_sem_value--;
+
+ ldap_pvt_thread_mutex_unlock( &ls->ls_mutex );
+
+ return 0;
+}
+
+/*
+ * Increment the count by one and test if it is greater or
+ * equal to lazyness. If it is, wake up a blocked thread.
+ */
+int
+ldap_lazy_sem_post( ldap_lazy_sem_t* ls )
+{
+ if( ls == NULL ) return (-1);
+
+ ldap_pvt_thread_mutex_lock( &ls->ls_mutex );
+
+ ls->ls_sem_value++;
+ if ( ls->ls_wait ) {
+ if ( ls->ls_sem_value >= ls->ls_lazy_count ) {
+ ls->ls_wait = 0;
+ ldap_pvt_thread_cond_signal( &ls->ls_cond );
+ }
+ }
+
+ ldap_pvt_thread_mutex_unlock( &ls->ls_mutex );
+
+ return 0;
+}
+