net: implements ip_route_input_noref()
[linux-2.6.git] / net / rds / threads.c
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;
71 EXPORT_SYMBOL_GPL(rds_wq);
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 }
93 EXPORT_SYMBOL_GPL(rds_connect_complete);
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_workqueue("krdsd");
263         if (rds_wq == NULL)
264                 return -ENOMEM;
265
266         return 0;
267 }