ITS#2959: provide reason for deferring operation in log message

Also, took away abandon operations blank check against deferment.
Abandon must be deferred in some cases (such as when other operations
are pending) and should be deferred in some other cases (such as too
many threads).

servers/slapd/connection.c

@@ -1435,8 +1435,7 @@ int connection_read(ber_socket_t s)
 
 static int
 connection_input(
-	Connection *conn
-)
+	Connection *conn )
 {
 	Operation *op;
 	ber_tag_t	tag;
@@ -1448,6 +1447,7 @@ connection_input(
 	Sockaddr	peeraddr;
 	char 		*cdn = NULL;
 #endif
+	char *defer = NULL;
 
 	if ( conn->c_currentber == NULL &&
 		( conn->c_currentber = ber_alloc()) == NULL )
@@ -1617,28 +1617,34 @@ connection_input(
 	 * Bind, or if it's closing. Also, don't let any single conn
 	 * use up all the available threads, and don't execute if we're
 	 * currently blocked on output. And don't execute if there are
-	 * already pending ops, let them go first.
-	 *
-	 * But always allow Abandon through; it won't cost much.
+	 * already pending ops, let them go first.  Abandon operations
+	 * get exceptions to some, but not all, cases.
 	 */
-	if ( tag != LDAP_REQ_ABANDON && (conn->c_conn_state == SLAP_C_BINDING
-		|| conn->c_conn_state == SLAP_C_CLOSING
-		|| conn->c_n_ops_executing >= connection_pool_max/2
-		|| conn->c_n_ops_pending
-		|| conn->c_writewaiter))
-	{
+	if (tag != LDAP_REQ_ABANDON && conn->c_conn_state == SLAP_C_CLOSING) {
+		defer = "closing";
+	} else if (tag != LDAP_REQ_ABANDON && conn->c_writewaiter) {
+		defer = "awaiting write";
+	} else if (conn->c_n_ops_executing >= connection_pool_max/2) {
+		defer = "too many executing";
+	} else if (conn->c_conn_state == SLAP_C_BINDING ) {
+		defer = "binding";
+	} else if (conn->c_n_ops_pending) {
+		defer = "pending operations";
+	}
+
+	if( defer ) {
 		int max = conn->c_dn.bv_len
 			? slap_conn_max_pending_auth
 			: slap_conn_max_pending;
 
 #ifdef NEW_LOGGING
 		LDAP_LOG( CONNECTION, INFO, 
-			"connection_input: conn %lu deferring operation\n",
-			conn->c_connid, 0, 0 );
+			"connection_input: conn %lu deferring operation: %s\n",
+			conn->c_connid, defer, 0 );
 #else
 		Debug( LDAP_DEBUG_ANY,
-			"connection_input: conn=%lu deferring operation\n",
-			conn->c_connid, 0, 0 );
+			"connection_input: conn=%lu deferring operation: %s\n",
+			conn->c_connid, defer, 0 );
 #endif
 		conn->c_n_ops_pending++;
 		LDAP_STAILQ_INSERT_TAIL( &conn->c_pending_ops, op, o_next );