linux/net/rds/threads.c

/*
 * Copyright (c) 2006, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 */
#include <linux/kernel.h>
#include <linux/random.h>
#include <linux/export.h>

#include "rds.h"

/*
 * All of connection management is simplified by serializing it through
 * work queues that execute in a connection managing thread.
 *
 * TCP wants to send acks through sendpage() in response to data_ready(),
 * but it needs a process context to do so.
 *
 * The receive paths need to allocate but can't drop packets (!) so we have
 * a thread around to block allocating if the receive fast path sees an
 * allocation failure.
 */

/* Grand Unified Theory of connection life cycle:
 * At any point in time, the connection can be in one of these states:
 * DOWN, CONNECTING, UP, DISCONNECTING, ERROR
 *
 * The following transitions are possible:
 *  ANY		  -> ERROR
 *  UP		  -> DISCONNECTING
 *  ERROR	  -> DISCONNECTING
 *  DISCONNECTING -> DOWN
 *  DOWN	  -> CONNECTING
 *  CONNECTING	  -> UP
 *
 * Transition to state DISCONNECTING/DOWN:
 *  -	Inside the shutdown worker; synchronizes with xmit path
 *	through RDS_IN_XMIT, and with connection management callbacks
 *	via c_cm_lock.
 *
 *	For receive callbacks, we rely on the underlying transport
 *	(TCP, IB/RDMA) to provide the necessary synchronisation.
 */
struct workqueue_struct *rds_wq;
EXPORT_SYMBOL_GPL(…);

void rds_connect_path_complete(struct rds_conn_path *cp, int curr)
{ … }
EXPORT_SYMBOL_GPL(…);

void rds_connect_complete(struct rds_connection *conn)
{ … }
EXPORT_SYMBOL_GPL(…);

/*
 * This random exponential backoff is relied on to eventually resolve racing
 * connects.
 *
 * If connect attempts race then both parties drop both connections and come
 * here to wait for a random amount of time before trying again.  Eventually
 * the backoff range will be so much greater than the time it takes to
 * establish a connection that one of the pair will establish the connection
 * before the other's random delay fires.
 *
 * Connection attempts that arrive while a connection is already established
 * are also considered to be racing connects.  This lets a connection from
 * a rebooted machine replace an existing stale connection before the transport
 * notices that the connection has failed.
 *
 * We should *always* start with a random backoff; otherwise a broken connection
 * will always take several iterations to be re-established.
 */
void rds_queue_reconnect(struct rds_conn_path *cp)
{ … }

void rds_connect_worker(struct work_struct *work)
{ … }

void rds_send_worker(struct work_struct *work)
{ … }

void rds_recv_worker(struct work_struct *work)
{ … }

void rds_shutdown_worker(struct work_struct *work)
{ … }

void rds_threads_exit(void)
{ … }

int rds_threads_init(void)
{ … }

/* Compare two IPv6 addresses.  Return 0 if the two addresses are equal.
 * Return 1 if the first is greater.  Return -1 if the second is greater.
 */
int rds_addr_cmp(const struct in6_addr *addr1,
		 const struct in6_addr *addr2)
{ … }
EXPORT_SYMBOL_GPL(…);