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_connection *conn, int curr) 75 { 76 if (!rds_conn_transition(conn, 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(&conn->c_state)); 81 rds_conn_drop(conn); 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_path_complete); 94 95 void rds_connect_complete(struct rds_connection *conn) 96 { 97 rds_connect_path_complete(conn, 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_connection *conn) 120 { 121 unsigned long rand; 122 123 rdsdebug("conn %p for %pI4 to %pI4 reconnect jiffies %lu\n", 124 conn, &conn->c_laddr, &conn->c_faddr, 125 conn->c_reconnect_jiffies); 126 127 set_bit(RDS_RECONNECT_PENDING, &conn->c_flags); 128 if (conn->c_reconnect_jiffies == 0) { 129 conn->c_reconnect_jiffies = rds_sysctl_reconnect_min_jiffies; 130 queue_delayed_work(rds_wq, &conn->c_conn_w, 0); 131 return; 132 } 133 134 get_random_bytes(&rand, sizeof(rand)); 135 rdsdebug("%lu delay %lu ceil conn %p for %pI4 -> %pI4\n", 136 rand % conn->c_reconnect_jiffies, conn->c_reconnect_jiffies, 137 conn, &conn->c_laddr, &conn->c_faddr); 138 queue_delayed_work(rds_wq, &conn->c_conn_w, 139 rand % conn->c_reconnect_jiffies); 140 141 conn->c_reconnect_jiffies = min(conn->c_reconnect_jiffies * 2, 142 rds_sysctl_reconnect_max_jiffies); 143 } 144 145 void rds_connect_worker(struct work_struct *work) 146 { 147 struct rds_connection *conn = container_of(work, struct rds_connection, c_conn_w.work); 148 int ret; 149 150 clear_bit(RDS_RECONNECT_PENDING, &conn->c_flags); 151 if (rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_CONNECTING)) { 152 ret = conn->c_trans->conn_connect(conn); 153 rdsdebug("conn %p for %pI4 to %pI4 dispatched, ret %d\n", 154 conn, &conn->c_laddr, &conn->c_faddr, ret); 155 156 if (ret) { 157 if (rds_conn_transition(conn, RDS_CONN_CONNECTING, RDS_CONN_DOWN)) 158 rds_queue_reconnect(conn); 159 else 160 rds_conn_error(conn, "RDS: connect failed\n"); 161 } 162 } 163 } 164 165 void rds_send_worker(struct work_struct *work) 166 { 167 struct rds_connection *conn = container_of(work, struct rds_connection, c_send_w.work); 168 int ret; 169 170 if (rds_conn_state(conn) == RDS_CONN_UP) { 171 clear_bit(RDS_LL_SEND_FULL, &conn->c_flags); 172 ret = rds_send_xmit(conn); 173 cond_resched(); 174 rdsdebug("conn %p ret %d\n", conn, ret); 175 switch (ret) { 176 case -EAGAIN: 177 rds_stats_inc(s_send_immediate_retry); 178 queue_delayed_work(rds_wq, &conn->c_send_w, 0); 179 break; 180 case -ENOMEM: 181 rds_stats_inc(s_send_delayed_retry); 182 queue_delayed_work(rds_wq, &conn->c_send_w, 2); 183 default: 184 break; 185 } 186 } 187 } 188 189 void rds_recv_worker(struct work_struct *work) 190 { 191 struct rds_connection *conn = container_of(work, struct rds_connection, c_recv_w.work); 192 int ret; 193 194 if (rds_conn_state(conn) == RDS_CONN_UP) { 195 ret = conn->c_trans->recv(conn); 196 rdsdebug("conn %p ret %d\n", conn, ret); 197 switch (ret) { 198 case -EAGAIN: 199 rds_stats_inc(s_recv_immediate_retry); 200 queue_delayed_work(rds_wq, &conn->c_recv_w, 0); 201 break; 202 case -ENOMEM: 203 rds_stats_inc(s_recv_delayed_retry); 204 queue_delayed_work(rds_wq, &conn->c_recv_w, 2); 205 default: 206 break; 207 } 208 } 209 } 210 211 void rds_shutdown_worker(struct work_struct *work) 212 { 213 struct rds_connection *conn = container_of(work, struct rds_connection, c_down_w); 214 215 rds_conn_shutdown(conn); 216 } 217 218 void rds_threads_exit(void) 219 { 220 destroy_workqueue(rds_wq); 221 } 222 223 int rds_threads_init(void) 224 { 225 rds_wq = create_singlethread_workqueue("krdsd"); 226 if (!rds_wq) 227 return -ENOMEM; 228 229 return 0; 230 } 231