net/rds/threads.c - kernel/skids - Git at Google

 /*
  * Copyright (c) 2006 Oracle.  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 "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 c_send_lock, 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(rds_wq);

 void rds_connect_complete(struct rds_connection *conn)
 {
 	if (!rds_conn_transition(conn, RDS_CONN_CONNECTING, RDS_CONN_UP)) {
 		printk(KERN_WARNING "%s: Cannot transition to state UP, "
 				"current state is %d\n",
 				__func__,
 				atomic_read(&conn->c_state));
 		atomic_set(&conn->c_state, RDS_CONN_ERROR);
 		queue_work(rds_wq, &conn->c_down_w);
 		return;
 	}

 	rdsdebug("conn %p for %pI4 to %pI4 complete\n",
 	  conn, &conn->c_laddr, &conn->c_faddr);

 	conn->c_reconnect_jiffies = 0;
 	set_bit(0, &conn->c_map_queued);
 	queue_delayed_work(rds_wq, &conn->c_send_w, 0);
 	queue_delayed_work(rds_wq, &conn->c_recv_w, 0);
 }
 EXPORT_SYMBOL_GPL(rds_connect_complete);

 /*
  * 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.
  */
 static void rds_queue_reconnect(struct rds_connection *conn)
 {
 	unsigned long rand;

 	rdsdebug("conn %p for %pI4 to %pI4 reconnect jiffies %lu\n",
 	  conn, &conn->c_laddr, &conn->c_faddr,
 	  conn->c_reconnect_jiffies);

 	set_bit(RDS_RECONNECT_PENDING, &conn->c_flags);
 	if (conn->c_reconnect_jiffies == 0) {
 		conn->c_reconnect_jiffies = rds_sysctl_reconnect_min_jiffies;
 		queue_delayed_work(rds_wq, &conn->c_conn_w, 0);
 		return;
 	}

 	get_random_bytes(&rand, sizeof(rand));
 	rdsdebug("%lu delay %lu ceil conn %p for %pI4 -> %pI4\n",
 		 rand % conn->c_reconnect_jiffies, conn->c_reconnect_jiffies,
 		 conn, &conn->c_laddr, &conn->c_faddr);
 	queue_delayed_work(rds_wq, &conn->c_conn_w,
 			   rand % conn->c_reconnect_jiffies);

 	conn->c_reconnect_jiffies = min(conn->c_reconnect_jiffies * 2,
 					rds_sysctl_reconnect_max_jiffies);
 }

 void rds_connect_worker(struct work_struct *work)
 {
 	struct rds_connection *conn = container_of(work, struct rds_connection, c_conn_w.work);
 	int ret;

 	clear_bit(RDS_RECONNECT_PENDING, &conn->c_flags);
 	if (rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_CONNECTING)) {
 		ret = conn->c_trans->conn_connect(conn);
 		rdsdebug("conn %p for %pI4 to %pI4 dispatched, ret %d\n",
 			conn, &conn->c_laddr, &conn->c_faddr, ret);

 		if (ret) {
 			if (rds_conn_transition(conn, RDS_CONN_CONNECTING, RDS_CONN_DOWN))
 				rds_queue_reconnect(conn);
 			else
 				rds_conn_error(conn, "RDS: connect failed\n");
 		}
 	}
 }

 void rds_shutdown_worker(struct work_struct *work)
 {
 	struct rds_connection *conn = container_of(work, struct rds_connection, c_down_w);

 	/* shut it down unless it's down already */
 	if (!rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_DOWN)) {
 		/*
 		 * Quiesce the connection mgmt handlers before we start tearing
 		 * things down. We don't hold the mutex for the entire
 		 * duration of the shutdown operation, else we may be
 		 * deadlocking with the CM handler. Instead, the CM event
 		 * handler is supposed to check for state DISCONNECTING
 		 */
 		mutex_lock(&conn->c_cm_lock);
 		if (!rds_conn_transition(conn, RDS_CONN_UP, RDS_CONN_DISCONNECTING) &&
 		    !rds_conn_transition(conn, RDS_CONN_ERROR, RDS_CONN_DISCONNECTING)) {
 			rds_conn_error(conn, "shutdown called in state %d\n",
 					atomic_read(&conn->c_state));
 			mutex_unlock(&conn->c_cm_lock);
 			return;
 		}
 		mutex_unlock(&conn->c_cm_lock);

 		mutex_lock(&conn->c_send_lock);
 		conn->c_trans->conn_shutdown(conn);
 		rds_conn_reset(conn);
 		mutex_unlock(&conn->c_send_lock);

 		if (!rds_conn_transition(conn, RDS_CONN_DISCONNECTING, RDS_CONN_DOWN)) {
 			/* This can happen - eg when we're in the middle of tearing
 			 * down the connection, and someone unloads the rds module.
 			 * Quite reproduceable with loopback connections.
 			 * Mostly harmless.
 			 */
 			rds_conn_error(conn,
 				"%s: failed to transition to state DOWN, "
 				"current state is %d\n",
 				__func__,
 				atomic_read(&conn->c_state));
 			return;
 		}
 	}

 	/* Then reconnect if it's still live.
 	 * The passive side of an IB loopback connection is never added
 	 * to the conn hash, so we never trigger a reconnect on this
 	 * conn - the reconnect is always triggered by the active peer. */
 	cancel_delayed_work(&conn->c_conn_w);
 	if (!hlist_unhashed(&conn->c_hash_node))
 		rds_queue_reconnect(conn);
 }

 void rds_send_worker(struct work_struct *work)
 {
 	struct rds_connection *conn = container_of(work, struct rds_connection, c_send_w.work);
 	int ret;

 	if (rds_conn_state(conn) == RDS_CONN_UP) {
 		ret = rds_send_xmit(conn);
 		rdsdebug("conn %p ret %d\n", conn, ret);
 		switch (ret) {
 		case -EAGAIN:
 			rds_stats_inc(s_send_immediate_retry);
 			queue_delayed_work(rds_wq, &conn->c_send_w, 0);
 			break;
 		case -ENOMEM:
 			rds_stats_inc(s_send_delayed_retry);
 			queue_delayed_work(rds_wq, &conn->c_send_w, 2);
 		default:
 			break;
 		}
 	}
 }

 void rds_recv_worker(struct work_struct *work)
 {
 	struct rds_connection *conn = container_of(work, struct rds_connection, c_recv_w.work);
 	int ret;

 	if (rds_conn_state(conn) == RDS_CONN_UP) {
 		ret = conn->c_trans->recv(conn);
 		rdsdebug("conn %p ret %d\n", conn, ret);
 		switch (ret) {
 		case -EAGAIN:
 			rds_stats_inc(s_recv_immediate_retry);
 			queue_delayed_work(rds_wq, &conn->c_recv_w, 0);
 			break;
 		case -ENOMEM:
 			rds_stats_inc(s_recv_delayed_retry);
 			queue_delayed_work(rds_wq, &conn->c_recv_w, 2);
 		default:
 			break;
 		}
 	}
 }

 void rds_threads_exit(void)
 {
 	destroy_workqueue(rds_wq);
 }

 int __init rds_threads_init(void)
 {
 	rds_wq = create_workqueue("krdsd");
 	if (rds_wq == NULL)
 		return -ENOMEM;

 	return 0;
 }
	/*
	* Copyright (c) 2006 Oracle. 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 "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 c_send_lock, 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(rds_wq);

	void rds_connect_complete(struct rds_connection *conn)
	{
	if (!rds_conn_transition(conn, RDS_CONN_CONNECTING, RDS_CONN_UP)) {
	printk(KERN_WARNING "%s: Cannot transition to state UP, "
	"current state is %d\n",
	__func__,
	atomic_read(&conn->c_state));
	atomic_set(&conn->c_state, RDS_CONN_ERROR);
	queue_work(rds_wq, &conn->c_down_w);
	return;
	}

	rdsdebug("conn %p for %pI4 to %pI4 complete\n",
	conn, &conn->c_laddr, &conn->c_faddr);

	conn->c_reconnect_jiffies = 0;
	set_bit(0, &conn->c_map_queued);
	queue_delayed_work(rds_wq, &conn->c_send_w, 0);
	queue_delayed_work(rds_wq, &conn->c_recv_w, 0);
	}
	EXPORT_SYMBOL_GPL(rds_connect_complete);

	/*
	* 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.
	*/
	static void rds_queue_reconnect(struct rds_connection *conn)
	{
	unsigned long rand;

	rdsdebug("conn %p for %pI4 to %pI4 reconnect jiffies %lu\n",
	conn, &conn->c_laddr, &conn->c_faddr,
	conn->c_reconnect_jiffies);

	set_bit(RDS_RECONNECT_PENDING, &conn->c_flags);
	if (conn->c_reconnect_jiffies == 0) {
	conn->c_reconnect_jiffies = rds_sysctl_reconnect_min_jiffies;
	queue_delayed_work(rds_wq, &conn->c_conn_w, 0);
	return;
	}

	get_random_bytes(&rand, sizeof(rand));
	rdsdebug("%lu delay %lu ceil conn %p for %pI4 -> %pI4\n",
	rand % conn->c_reconnect_jiffies, conn->c_reconnect_jiffies,
	conn, &conn->c_laddr, &conn->c_faddr);
	queue_delayed_work(rds_wq, &conn->c_conn_w,
	rand % conn->c_reconnect_jiffies);

	conn->c_reconnect_jiffies = min(conn->c_reconnect_jiffies * 2,
	rds_sysctl_reconnect_max_jiffies);
	}

	void rds_connect_worker(struct work_struct *work)
	{
	struct rds_connection *conn = container_of(work, struct rds_connection, c_conn_w.work);
	int ret;

	clear_bit(RDS_RECONNECT_PENDING, &conn->c_flags);
	if (rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_CONNECTING)) {
	ret = conn->c_trans->conn_connect(conn);
	rdsdebug("conn %p for %pI4 to %pI4 dispatched, ret %d\n",
	conn, &conn->c_laddr, &conn->c_faddr, ret);

	if (ret) {
	if (rds_conn_transition(conn, RDS_CONN_CONNECTING, RDS_CONN_DOWN))
	rds_queue_reconnect(conn);
	else
	rds_conn_error(conn, "RDS: connect failed\n");
	}
	}
	}

	void rds_shutdown_worker(struct work_struct *work)
	{
	struct rds_connection *conn = container_of(work, struct rds_connection, c_down_w);

	/* shut it down unless it's down already */
	if (!rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_DOWN)) {
	/*
	* Quiesce the connection mgmt handlers before we start tearing
	* things down. We don't hold the mutex for the entire
	* duration of the shutdown operation, else we may be
	* deadlocking with the CM handler. Instead, the CM event
	* handler is supposed to check for state DISCONNECTING
	*/
	mutex_lock(&conn->c_cm_lock);
	if (!rds_conn_transition(conn, RDS_CONN_UP, RDS_CONN_DISCONNECTING) &&
	!rds_conn_transition(conn, RDS_CONN_ERROR, RDS_CONN_DISCONNECTING)) {
	rds_conn_error(conn, "shutdown called in state %d\n",
	atomic_read(&conn->c_state));
	mutex_unlock(&conn->c_cm_lock);
	return;
	}
	mutex_unlock(&conn->c_cm_lock);

	mutex_lock(&conn->c_send_lock);
	conn->c_trans->conn_shutdown(conn);
	rds_conn_reset(conn);
	mutex_unlock(&conn->c_send_lock);

	if (!rds_conn_transition(conn, RDS_CONN_DISCONNECTING, RDS_CONN_DOWN)) {
	/* This can happen - eg when we're in the middle of tearing
	* down the connection, and someone unloads the rds module.
	* Quite reproduceable with loopback connections.
	* Mostly harmless.
	*/
	rds_conn_error(conn,
	"%s: failed to transition to state DOWN, "
	"current state is %d\n",
	__func__,
	atomic_read(&conn->c_state));
	return;
	}
	}

	/* Then reconnect if it's still live.
	* The passive side of an IB loopback connection is never added
	* to the conn hash, so we never trigger a reconnect on this
	* conn - the reconnect is always triggered by the active peer. */
	cancel_delayed_work(&conn->c_conn_w);
	if (!hlist_unhashed(&conn->c_hash_node))
	rds_queue_reconnect(conn);
	}

	void rds_send_worker(struct work_struct *work)
	{
	struct rds_connection *conn = container_of(work, struct rds_connection, c_send_w.work);
	int ret;

	if (rds_conn_state(conn) == RDS_CONN_UP) {
	ret = rds_send_xmit(conn);
	rdsdebug("conn %p ret %d\n", conn, ret);
	switch (ret) {
	case -EAGAIN:
	rds_stats_inc(s_send_immediate_retry);
	queue_delayed_work(rds_wq, &conn->c_send_w, 0);
	break;
	case -ENOMEM:
	rds_stats_inc(s_send_delayed_retry);
	queue_delayed_work(rds_wq, &conn->c_send_w, 2);
	default:
	break;
	}
	}
	}

	void rds_recv_worker(struct work_struct *work)
	{
	struct rds_connection *conn = container_of(work, struct rds_connection, c_recv_w.work);
	int ret;

	if (rds_conn_state(conn) == RDS_CONN_UP) {
	ret = conn->c_trans->recv(conn);
	rdsdebug("conn %p ret %d\n", conn, ret);
	switch (ret) {
	case -EAGAIN:
	rds_stats_inc(s_recv_immediate_retry);
	queue_delayed_work(rds_wq, &conn->c_recv_w, 0);
	break;
	case -ENOMEM:
	rds_stats_inc(s_recv_delayed_retry);
	queue_delayed_work(rds_wq, &conn->c_recv_w, 2);
	default:
	break;
	}
	}
	}

	void rds_threads_exit(void)
	{
	destroy_workqueue(rds_wq);
	}

	int __init rds_threads_init(void)
	{
	rds_wq = create_workqueue("krdsd");
	if (rds_wq == NULL)
	return -ENOMEM;

	return 0;
	}