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 } 268