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 #include <linux/export.h> 36 37 #include "rds.h" 38 39 /* 40 * All of connection management is simplified by serializing it through 41 * work queues that execute in a connection managing thread. 42 * 43 * TCP wants to send acks through sendpage() in response to data_ready(), 44 * but it needs a process context to do so. 45 * 46 * The receive paths need to allocate but can't drop packets (!) so we have 47 * a thread around to block allocating if the receive fast path sees an 48 * allocation failure. 49 */ 50 51 /* Grand Unified Theory of connection life cycle: 52 * At any point in time, the connection can be in one of these states: 53 * DOWN, CONNECTING, UP, DISCONNECTING, ERROR 54 * 55 * The following transitions are possible: 56 * ANY -> ERROR 57 * UP -> DISCONNECTING 58 * ERROR -> DISCONNECTING 59 * DISCONNECTING -> DOWN 60 * DOWN -> CONNECTING 61 * CONNECTING -> UP 62 * 63 * Transition to state DISCONNECTING/DOWN: 64 * - Inside the shutdown worker; synchronizes with xmit path 65 * through RDS_IN_XMIT, and with connection management callbacks 66 * via c_cm_lock. 67 * 68 * For receive callbacks, we rely on the underlying transport 69 * (TCP, IB/RDMA) to provide the necessary synchronisation. 70 */ 71 struct workqueue_struct *rds_wq; 72 EXPORT_SYMBOL_GPL(rds_wq); 73 74 void rds_connect_path_complete(struct rds_conn_path *cp, int curr) 75 { 76 if (!rds_conn_path_transition(cp, curr, RDS_CONN_UP)) { 77 printk(KERN_WARNING "%s: Cannot transition to state UP, " 78 "current state is %d\n", 79 __func__, 80 atomic_read(&cp->cp_state)); 81 rds_conn_path_drop(cp); 82 return; 83 } 84 85 rdsdebug("conn %p for %pI4 to %pI4 complete\n", 86 cp->cp_conn, &cp->cp_conn->c_laddr, &cp->cp_conn->c_faddr); 87 88 cp->cp_reconnect_jiffies = 0; 89 set_bit(0, &cp->cp_conn->c_map_queued); 90 queue_delayed_work(rds_wq, &cp->cp_send_w, 0); 91 queue_delayed_work(rds_wq, &cp->cp_recv_w, 0); 92 } 93 EXPORT_SYMBOL_GPL(rds_connect_path_complete); 94 95 void rds_connect_complete(struct rds_connection *conn) 96 { 97 rds_connect_path_complete(&conn->c_path[0], RDS_CONN_CONNECTING); 98 } 99 EXPORT_SYMBOL_GPL(rds_connect_complete); 100 101 /* 102 * This random exponential backoff is relied on to eventually resolve racing 103 * connects. 104 * 105 * If connect attempts race then both parties drop both connections and come 106 * here to wait for a random amount of time before trying again. Eventually 107 * the backoff range will be so much greater than the time it takes to 108 * establish a connection that one of the pair will establish the connection 109 * before the other's random delay fires. 110 * 111 * Connection attempts that arrive while a connection is already established 112 * are also considered to be racing connects. This lets a connection from 113 * a rebooted machine replace an existing stale connection before the transport 114 * notices that the connection has failed. 115 * 116 * We should *always* start with a random backoff; otherwise a broken connection 117 * will always take several iterations to be re-established. 118 */ 119 void rds_queue_reconnect(struct rds_conn_path *cp) 120 { 121 unsigned long rand; 122 struct rds_connection *conn = cp->cp_conn; 123 124 rdsdebug("conn %p for %pI4 to %pI4 reconnect jiffies %lu\n", 125 conn, &conn->c_laddr, &conn->c_faddr, 126 cp->cp_reconnect_jiffies); 127 128 set_bit(RDS_RECONNECT_PENDING, &cp->cp_flags); 129 if (cp->cp_reconnect_jiffies == 0) { 130 cp->cp_reconnect_jiffies = rds_sysctl_reconnect_min_jiffies; 131 queue_delayed_work(rds_wq, &cp->cp_conn_w, 0); 132 return; 133 } 134 135 get_random_bytes(&rand, sizeof(rand)); 136 rdsdebug("%lu delay %lu ceil conn %p for %pI4 -> %pI4\n", 137 rand % cp->cp_reconnect_jiffies, cp->cp_reconnect_jiffies, 138 conn, &conn->c_laddr, &conn->c_faddr); 139 queue_delayed_work(rds_wq, &cp->cp_conn_w, 140 rand % cp->cp_reconnect_jiffies); 141 142 cp->cp_reconnect_jiffies = min(cp->cp_reconnect_jiffies * 2, 143 rds_sysctl_reconnect_max_jiffies); 144 } 145 146 void rds_connect_worker(struct work_struct *work) 147 { 148 struct rds_conn_path *cp = container_of(work, 149 struct rds_conn_path, 150 cp_conn_w.work); 151 struct rds_connection *conn = cp->cp_conn; 152 int ret; 153 154 clear_bit(RDS_RECONNECT_PENDING, &cp->cp_flags); 155 if (rds_conn_path_transition(cp, RDS_CONN_DOWN, RDS_CONN_CONNECTING)) { 156 ret = conn->c_trans->conn_connect(conn); 157 rdsdebug("conn %p for %pI4 to %pI4 dispatched, ret %d\n", 158 conn, &conn->c_laddr, &conn->c_faddr, ret); 159 160 if (ret) { 161 if (rds_conn_path_transition(cp, 162 RDS_CONN_CONNECTING, 163 RDS_CONN_DOWN)) 164 rds_queue_reconnect(cp); 165 else 166 rds_conn_error(conn, "RDS: connect failed\n"); 167 } 168 } 169 } 170 171 void rds_send_worker(struct work_struct *work) 172 { 173 struct rds_conn_path *cp = container_of(work, 174 struct rds_conn_path, 175 cp_send_w.work); 176 int ret; 177 178 if (rds_conn_path_state(cp) == RDS_CONN_UP) { 179 clear_bit(RDS_LL_SEND_FULL, &cp->cp_flags); 180 ret = rds_send_xmit(cp->cp_conn); 181 cond_resched(); 182 rdsdebug("conn %p ret %d\n", cp->cp_conn, ret); 183 switch (ret) { 184 case -EAGAIN: 185 rds_stats_inc(s_send_immediate_retry); 186 queue_delayed_work(rds_wq, &cp->cp_send_w, 0); 187 break; 188 case -ENOMEM: 189 rds_stats_inc(s_send_delayed_retry); 190 queue_delayed_work(rds_wq, &cp->cp_send_w, 2); 191 default: 192 break; 193 } 194 } 195 } 196 197 void rds_recv_worker(struct work_struct *work) 198 { 199 struct rds_conn_path *cp = container_of(work, 200 struct rds_conn_path, 201 cp_recv_w.work); 202 int ret; 203 204 if (rds_conn_path_state(cp) == RDS_CONN_UP) { 205 ret = cp->cp_conn->c_trans->recv(cp->cp_conn); 206 rdsdebug("conn %p ret %d\n", cp->cp_conn, ret); 207 switch (ret) { 208 case -EAGAIN: 209 rds_stats_inc(s_recv_immediate_retry); 210 queue_delayed_work(rds_wq, &cp->cp_recv_w, 0); 211 break; 212 case -ENOMEM: 213 rds_stats_inc(s_recv_delayed_retry); 214 queue_delayed_work(rds_wq, &cp->cp_recv_w, 2); 215 default: 216 break; 217 } 218 } 219 } 220 221 void rds_shutdown_worker(struct work_struct *work) 222 { 223 struct rds_conn_path *cp = container_of(work, 224 struct rds_conn_path, 225 cp_down_w); 226 227 rds_conn_shutdown(cp->cp_conn); 228 } 229 230 void rds_threads_exit(void) 231 { 232 destroy_workqueue(rds_wq); 233 } 234 235 int rds_threads_init(void) 236 { 237 rds_wq = create_singlethread_workqueue("krdsd"); 238 if (!rds_wq) 239 return -ENOMEM; 240 241 return 0; 242 } 243