ITS#9338 alternate fix

Don't resume pending ops unless there are no other threads
waiting to write

servers/slapd/connection.c

@@ -2039,6 +2039,34 @@ int connection_write(ber_socket_t s)
 	return 0;
 }
 
+int connection_write_resume( Connection *c )
+{
+	Operation *op;
+
+	ldap_pvt_thread_mutex_lock( &c->c_mutex );
+	/* If there are ops pending because of a writewaiter,
+	 * start one up.
+	 */
+	while ((op = LDAP_STAILQ_FIRST( &c->c_pending_ops )) != NULL) {
+		if ( c->c_n_ops_executing > connection_pool_max/2 ) break;
+
+		LDAP_STAILQ_REMOVE_HEAD( &c->c_pending_ops, o_next );
+		LDAP_STAILQ_NEXT(op, o_next) = NULL;
+
+		/* pending operations should not be marked for abandonment */
+		assert(!op->o_abandon);
+
+		c->c_n_ops_pending--;
+		c->c_n_ops_executing++;
+
+		connection_op_activate( op );
+
+		break;
+	}
+
+	connection_return( c );
+}
+
 #ifdef LDAP_SLAPI
 typedef struct conn_fake_extblock {
 	void *eb_conn;

servers/slapd/proto-slap.h

@@ -809,6 +809,7 @@ LDAP_SLAPD_F (const char *) connection_state2str LDAP_P(( int state ))
 
 LDAP_SLAPD_F (int) connection_read_activate LDAP_P((ber_socket_t s));
 LDAP_SLAPD_F (int) connection_write LDAP_P((ber_socket_t s));
+LDAP_SLAPD_F (int) connection_write_resume LDAP_P((Connection *c));
 
 LDAP_SLAPD_F (void) connection_op_finish LDAP_P((
 	Operation *op ));

servers/slapd/result.c

@@ -339,6 +339,7 @@ static long send_ldap_ber(
 	ber_len_t bytes;
 	long ret = 0;
 	char *close_reason;
+	int do_resume = 0;
 
 	ber_get_option( ber, LBER_OPT_BER_BYTES_TO_WRITE, &bytes );
 
@@ -404,11 +405,13 @@ fail:
 		}
 
 		/* wait for socket to be write-ready */
+		do_resume = 1;
 		conn->c_writewaiter = 1;
 		ldap_pvt_thread_mutex_unlock( &conn->c_write1_mutex );
 		ldap_pvt_thread_pool_idle( &connection_pool );
 		slap_writewait_play( op );
 		err = slapd_wait_writer( conn->c_sd );
+		conn->c_writewaiter = 0;
 		ldap_pvt_thread_pool_unidle( &connection_pool );
 		ldap_pvt_thread_mutex_lock( &conn->c_write1_mutex );
 		/* 0 is timeout, so we close it.
@@ -419,14 +422,9 @@ fail:
 				close_reason = "writetimeout";
 			else
 				close_reason = "connection lost on writewait";
-			conn->c_writewaiter = 0;
 			goto fail;
 		}
 
-		/* Resched connection if there are pending ops */
-		connection_write( conn->c_sd );
-		conn->c_writewaiter = 0;
-
 		if ( conn->c_writers < 0 ) {
 			ret = 0;
 			break;
@@ -435,15 +433,24 @@ fail:
 
 	conn->c_writing = 0;
 	if ( conn->c_writers < 0 ) {
+		/* shutting down, don't resume any ops */
+		do_resume = 0;
 		conn->c_writers++;
 		if ( !conn->c_writers )
 			ldap_pvt_thread_cond_signal( &conn->c_write1_cv );
 	} else {
 		conn->c_writers--;
+		/* other writers are waiting, don't resume any ops */
+		if ( conn->c_writers )
+			do_resume = 0;
 		ldap_pvt_thread_cond_signal( &conn->c_write1_cv );
 	}
 	ldap_pvt_thread_mutex_unlock( &conn->c_write1_mutex );
 
+	/* If there are no more writers, release a pending op */
+	if ( do_resume )
+		connection_write_resume( conn );
+
 	return ret;
 }