[net-next-2.6.git] / net / rds / threads.c

/*
 * 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_singlethread_workqueue("krdsd");
	if (rds_wq == NULL)
		return -ENOMEM;

	return 0;
}
Commit	Line	Data
00e0f34c AG	1	/*
	2	* Copyright (c) 2006 Oracle. All rights reserved.
	3	*
	4	* This software is available to you under a choice of one of two
	5	* licenses. You may choose to be licensed under the terms of the GNU
	6	* General Public License (GPL) Version 2, available from the file
	7	* COPYING in the main directory of this source tree, or the
	8	* OpenIB.org BSD license below:
	9	*
	10	* Redistribution and use in source and binary forms, with or
	11	* without modification, are permitted provided that the following
	12	* conditions are met:
	13	*
	14	* - Redistributions of source code must retain the above
	15	* copyright notice, this list of conditions and the following
	16	* disclaimer.
	17	*
	18	* - Redistributions in binary form must reproduce the above
	19	* copyright notice, this list of conditions and the following
	20	* disclaimer in the documentation and/or other materials
	21	* provided with the distribution.
	22	*
	23	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
	24	* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
	25	* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
	26	* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
	27	* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
	28	* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
	29	* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
	30	* SOFTWARE.
	31	*
	32	*/
	33	#include <linux/kernel.h>
	34	#include <linux/random.h>
	35
	36	#include "rds.h"
	37
	38	/*
	39	* All of connection management is simplified by serializing it through
	40	* work queues that execute in a connection managing thread.
	41	*
	42	* TCP wants to send acks through sendpage() in response to data_ready(),
	43	* but it needs a process context to do so.
	44	*
	45	* The receive paths need to allocate but can't drop packets (!) so we have
	46	* a thread around to block allocating if the receive fast path sees an
	47	* allocation failure.
	48	*/
	49
	50	/* Grand Unified Theory of connection life cycle:
	51	* At any point in time, the connection can be in one of these states:
	52	* DOWN, CONNECTING, UP, DISCONNECTING, ERROR
	53	*
	54	* The following transitions are possible:
	55	* ANY -> ERROR
	56	* UP -> DISCONNECTING
	57	* ERROR -> DISCONNECTING
	58	* DISCONNECTING -> DOWN
	59	* DOWN -> CONNECTING
	60	* CONNECTING -> UP
	61	*
	62	* Transition to state DISCONNECTING/DOWN:
	63	* - Inside the shutdown worker; synchronizes with xmit path
	64	* through c_send_lock, and with connection management callbacks
65	* via c_cm_lock.
66	*
67	* For receive callbacks, we rely on the underlying transport
68	* (TCP, IB/RDMA) to provide the necessary synchronisation.
69	*/
70	struct workqueue_struct *rds_wq;
616b757a	71	EXPORT_SYMBOL_GPL(rds_wq);
00e0f34c AG	72
	73	void rds_connect_complete(struct rds_connection *conn)
	74	{
	75	if (!rds_conn_transition(conn, RDS_CONN_CONNECTING, RDS_CONN_UP)) {
	76	printk(KERN_WARNING "%s: Cannot transition to state UP, "
	77	"current state is %d\n",
	78	__func__,
	79	atomic_read(&conn->c_state));
	80	atomic_set(&conn->c_state, RDS_CONN_ERROR);
	81	queue_work(rds_wq, &conn->c_down_w);
	82	return;
	83	}
	84
	85	rdsdebug("conn %p for %pI4 to %pI4 complete\n",
	86	conn, &conn->c_laddr, &conn->c_faddr);
	87
	88	conn->c_reconnect_jiffies = 0;
	89	set_bit(0, &conn->c_map_queued);
	90	queue_delayed_work(rds_wq, &conn->c_send_w, 0);
	91	queue_delayed_work(rds_wq, &conn->c_recv_w, 0);
	92	}
616b757a	93	EXPORT_SYMBOL_GPL(rds_connect_complete);
00e0f34c AG	94
	95	/*
	96	* This random exponential backoff is relied on to eventually resolve racing
	97	* connects.
	98	*
	99	* If connect attempts race then both parties drop both connections and come
	100	* here to wait for a random amount of time before trying again. Eventually
	101	* the backoff range will be so much greater than the time it takes to
	102	* establish a connection that one of the pair will establish the connection
	103	* before the other's random delay fires.
	104	*
	105	* Connection attempts that arrive while a connection is already established
	106	* are also considered to be racing connects. This lets a connection from
	107	* a rebooted machine replace an existing stale connection before the transport
	108	* notices that the connection has failed.
	109	*
	110	* We should always start with a random backoff; otherwise a broken connection
	111	* will always take several iterations to be re-established.
	112	*/
	113	static void rds_queue_reconnect(struct rds_connection *conn)
	114	{
	115	unsigned long rand;
	116
	117	rdsdebug("conn %p for %pI4 to %pI4 reconnect jiffies %lu\n",
	118	conn, &conn->c_laddr, &conn->c_faddr,
	119	conn->c_reconnect_jiffies);
	120
	121	set_bit(RDS_RECONNECT_PENDING, &conn->c_flags);
	122	if (conn->c_reconnect_jiffies == 0) {
	123	conn->c_reconnect_jiffies = rds_sysctl_reconnect_min_jiffies;
	124	queue_delayed_work(rds_wq, &conn->c_conn_w, 0);
	125	return;
	126	}
	127
	128	get_random_bytes(&rand, sizeof(rand));
	129	rdsdebug("%lu delay %lu ceil conn %p for %pI4 -> %pI4\n",
	130	rand % conn->c_reconnect_jiffies, conn->c_reconnect_jiffies,
	131	conn, &conn->c_laddr, &conn->c_faddr);
	132	queue_delayed_work(rds_wq, &conn->c_conn_w,
	133	rand % conn->c_reconnect_jiffies);
	134
	135	conn->c_reconnect_jiffies = min(conn->c_reconnect_jiffies * 2,
	136	rds_sysctl_reconnect_max_jiffies);
	137	}
	138
	139	void rds_connect_worker(struct work_struct *work)
	140	{
	141	struct rds_connection *conn = container_of(work, struct rds_connection, c_conn_w.work);
	142	int ret;
	143
	144	clear_bit(RDS_RECONNECT_PENDING, &conn->c_flags);
	145	if (rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_CONNECTING)) {
	146	ret = conn->c_trans->conn_connect(conn);
	147	rdsdebug("conn %p for %pI4 to %pI4 dispatched, ret %d\n",
	148	conn, &conn->c_laddr, &conn->c_faddr, ret);
	149
	150	if (ret) {
	151	if (rds_conn_transition(conn, RDS_CONN_CONNECTING, RDS_CONN_DOWN))
	152	rds_queue_reconnect(conn);
	153	else
	154	rds_conn_error(conn, "RDS: connect failed\n");
	155	}
	156	}
	157	}
158
159	void rds_shutdown_worker(struct work_struct *work)
160	{
161	struct rds_connection *conn = container_of(work, struct rds_connection, c_down_w);
162
163	/* shut it down unless it's down already */
164	if (!rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_DOWN)) {
165	/*
166	* Quiesce the connection mgmt handlers before we start tearing
167	* things down. We don't hold the mutex for the entire
168	* duration of the shutdown operation, else we may be
169	* deadlocking with the CM handler. Instead, the CM event
170	* handler is supposed to check for state DISCONNECTING
171	*/
172	mutex_lock(&conn->c_cm_lock);
173	if (!rds_conn_transition(conn, RDS_CONN_UP, RDS_CONN_DISCONNECTING)
174	&& !rds_conn_transition(conn, RDS_CONN_ERROR, RDS_CONN_DISCONNECTING)) {
175	rds_conn_error(conn, "shutdown called in state %d\n",
176	atomic_read(&conn->c_state));
177	mutex_unlock(&conn->c_cm_lock);
178	return;
179	}
180	mutex_unlock(&conn->c_cm_lock);
181
182	mutex_lock(&conn->c_send_lock);
183	conn->c_trans->conn_shutdown(conn);
184	rds_conn_reset(conn);
185	mutex_unlock(&conn->c_send_lock);
186
187	if (!rds_conn_transition(conn, RDS_CONN_DISCONNECTING, RDS_CONN_DOWN)) {
188	/* This can happen - eg when we're in the middle of tearing
189	* down the connection, and someone unloads the rds module.
190	* Quite reproduceable with loopback connections.
191	* Mostly harmless.
192	*/
193	rds_conn_error(conn,
194	"%s: failed to transition to state DOWN, "
195	"current state is %d\n",
196	__func__,
197	atomic_read(&conn->c_state));
198	return;
199	}
200	}
201
202	/* Then reconnect if it's still live.
203	* The passive side of an IB loopback connection is never added
204	* to the conn hash, so we never trigger a reconnect on this
205	* conn - the reconnect is always triggered by the active peer. */
206	cancel_delayed_work(&conn->c_conn_w);
207	if (!hlist_unhashed(&conn->c_hash_node))
208	rds_queue_reconnect(conn);
209	}
210
211	void rds_send_worker(struct work_struct *work)
212	{
213	struct rds_connection *conn = container_of(work, struct rds_connection, c_send_w.work);
214	int ret;
215
216	if (rds_conn_state(conn) == RDS_CONN_UP) {
217	ret = rds_send_xmit(conn);
218	rdsdebug("conn %p ret %d\n", conn, ret);
219	switch (ret) {
220	case -EAGAIN:
221	rds_stats_inc(s_send_immediate_retry);
222	queue_delayed_work(rds_wq, &conn->c_send_w, 0);
223	break;
224	case -ENOMEM:
225	rds_stats_inc(s_send_delayed_retry);
226	queue_delayed_work(rds_wq, &conn->c_send_w, 2);
227	default:
228	break;
229	}
230	}
231	}
232
233	void rds_recv_worker(struct work_struct *work)
234	{
235	struct rds_connection *conn = container_of(work, struct rds_connection, c_recv_w.work);
236	int ret;
237
238	if (rds_conn_state(conn) == RDS_CONN_UP) {
239	ret = conn->c_trans->recv(conn);
240	rdsdebug("conn %p ret %d\n", conn, ret);
241	switch (ret) {
242	case -EAGAIN:
243	rds_stats_inc(s_recv_immediate_retry);
244	queue_delayed_work(rds_wq, &conn->c_recv_w, 0);
245	break;
246	case -ENOMEM:
247	rds_stats_inc(s_recv_delayed_retry);
248	queue_delayed_work(rds_wq, &conn->c_recv_w, 2);
249	default:
250	break;
251	}
252	}
253	}
254
255	void rds_threads_exit(void)
256	{
257	destroy_workqueue(rds_wq);
258	}
259
260	int __init rds_threads_init(void)
261	{
262	rds_wq = create_singlethread_workqueue("krdsd");
263	if (rds_wq == NULL)
264	return -ENOMEM;
265
266	return 0;
267	}