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_complete(struct rds_connection *conn) 75 { 76 if (!rds_conn_transition(conn, RDS_CONN_CONNECTING, 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 atomic_set(&conn->c_state, RDS_CONN_ERROR); 82 queue_work(rds_wq, &conn->c_down_w); 83 return; 84 } 85 86 rdsdebug("conn %p for %pI4 to %pI4 complete\n", 87 conn, &conn->c_laddr, &conn->c_faddr); 88 89 conn->c_reconnect_jiffies = 0; 90 set_bit(0, &conn->c_map_queued); 91 queue_delayed_work(rds_wq, &conn->c_send_w, 0); 92 queue_delayed_work(rds_wq, &conn->c_recv_w, 0); 93 } 94 EXPORT_SYMBOL_GPL(rds_connect_complete); 95 96 /* 97 * This random exponential backoff is relied on to eventually resolve racing 98 * connects. 99 * 100 * If connect attempts race then both parties drop both connections and come 101 * here to wait for a random amount of time before trying again. Eventually 102 * the backoff range will be so much greater than the time it takes to 103 * establish a connection that one of the pair will establish the connection 104 * before the other's random delay fires. 105 * 106 * Connection attempts that arrive while a connection is already established 107 * are also considered to be racing connects. This lets a connection from 108 * a rebooted machine replace an existing stale connection before the transport 109 * notices that the connection has failed. 110 * 111 * We should *always* start with a random backoff; otherwise a broken connection 112 * will always take several iterations to be re-established. 113 */ 114 void rds_queue_reconnect(struct rds_connection *conn) 115 { 116 unsigned long rand; 117 118 rdsdebug("conn %p for %pI4 to %pI4 reconnect jiffies %lu\n", 119 conn, &conn->c_laddr, &conn->c_faddr, 120 conn->c_reconnect_jiffies); 121 122 set_bit(RDS_RECONNECT_PENDING, &conn->c_flags); 123 if (conn->c_reconnect_jiffies == 0) { 124 conn->c_reconnect_jiffies = rds_sysctl_reconnect_min_jiffies; 125 queue_delayed_work(rds_wq, &conn->c_conn_w, 0); 126 return; 127 } 128 129 get_random_bytes(&rand, sizeof(rand)); 130 rdsdebug("%lu delay %lu ceil conn %p for %pI4 -> %pI4\n", 131 rand % conn->c_reconnect_jiffies, conn->c_reconnect_jiffies, 132 conn, &conn->c_laddr, &conn->c_faddr); 133 queue_delayed_work(rds_wq, &conn->c_conn_w, 134 rand % conn->c_reconnect_jiffies); 135 136 conn->c_reconnect_jiffies = min(conn->c_reconnect_jiffies * 2, 137 rds_sysctl_reconnect_max_jiffies); 138 } 139 140 void rds_connect_worker(struct work_struct *work) 141 { 142 struct rds_connection *conn = container_of(work, struct rds_connection, c_conn_w.work); 143 int ret; 144 145 clear_bit(RDS_RECONNECT_PENDING, &conn->c_flags); 146 if (rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_CONNECTING)) { 147 ret = conn->c_trans->conn_connect(conn); 148 rdsdebug("conn %p for %pI4 to %pI4 dispatched, ret %d\n", 149 conn, &conn->c_laddr, &conn->c_faddr, ret); 150 151 if (ret) { 152 if (rds_conn_transition(conn, RDS_CONN_CONNECTING, RDS_CONN_DOWN)) 153 rds_queue_reconnect(conn); 154 else 155 rds_conn_error(conn, "RDS: connect failed\n"); 156 } 157 } 158 } 159 160 void rds_send_worker(struct work_struct *work) 161 { 162 struct rds_connection *conn = container_of(work, struct rds_connection, c_send_w.work); 163 int ret; 164 165 if (rds_conn_state(conn) == RDS_CONN_UP) { 166 ret = rds_send_xmit(conn); 167 rdsdebug("conn %p ret %d\n", conn, ret); 168 switch (ret) { 169 case -EAGAIN: 170 rds_stats_inc(s_send_immediate_retry); 171 queue_delayed_work(rds_wq, &conn->c_send_w, 0); 172 break; 173 case -ENOMEM: 174 rds_stats_inc(s_send_delayed_retry); 175 queue_delayed_work(rds_wq, &conn->c_send_w, 2); 176 default: 177 break; 178 } 179 } 180 } 181 182 void rds_recv_worker(struct work_struct *work) 183 { 184 struct rds_connection *conn = container_of(work, struct rds_connection, c_recv_w.work); 185 int ret; 186 187 if (rds_conn_state(conn) == RDS_CONN_UP) { 188 ret = conn->c_trans->recv(conn); 189 rdsdebug("conn %p ret %d\n", conn, ret); 190 switch (ret) { 191 case -EAGAIN: 192 rds_stats_inc(s_recv_immediate_retry); 193 queue_delayed_work(rds_wq, &conn->c_recv_w, 0); 194 break; 195 case -ENOMEM: 196 rds_stats_inc(s_recv_delayed_retry); 197 queue_delayed_work(rds_wq, &conn->c_recv_w, 2); 198 default: 199 break; 200 } 201 } 202 } 203 204 void rds_shutdown_worker(struct work_struct *work) 205 { 206 struct rds_connection *conn = container_of(work, struct rds_connection, c_down_w); 207 208 rds_conn_shutdown(conn); 209 } 210 211 void rds_threads_exit(void) 212 { 213 destroy_workqueue(rds_wq); 214 } 215 216 int rds_threads_init(void) 217 { 218 rds_wq = create_singlethread_workqueue("krdsd"); 219 if (!rds_wq) 220 return -ENOMEM; 221 222 return 0; 223 } 224