/* * Copyright (c) 2006 Oracle. All rights reserved. * * This software is available to you under a choice of one of two * licenses. You may choose to be licensed under the terms of the GNU * General Public License (GPL) Version 2, available from the file * COPYING in the main directory of this source tree, or the * OpenIB.org BSD license below: * * Redistribution and use in source and binary forms, with or * without modification, are permitted provided that the following * conditions are met: * * - Redistributions of source code must retain the above * copyright notice, this list of conditions and the following * disclaimer. * * - Redistributions in binary form must reproduce the above * copyright notice, this list of conditions and the following * disclaimer in the documentation and/or other materials * provided with the distribution. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. * */ #include <linux/kernel.h> #include <linux/random.h> #include <linux/export.h> #include "rds.h" /* * All of connection management is simplified by serializing it through * work queues that execute in a connection managing thread. * * TCP wants to send acks through sendpage() in response to data_ready(), * but it needs a process context to do so. * * The receive paths need to allocate but can't drop packets (!) so we have * a thread around to block allocating if the receive fast path sees an * allocation failure. */ /* Grand Unified Theory of connection life cycle: * At any point in time, the connection can be in one of these states: * DOWN, CONNECTING, UP, DISCONNECTING, ERROR * * The following transitions are possible: * ANY -> ERROR * UP -> DISCONNECTING * ERROR -> DISCONNECTING * DISCONNECTING -> DOWN * DOWN -> CONNECTING * CONNECTING -> UP * * Transition to state DISCONNECTING/DOWN: * - Inside the shutdown worker; synchronizes with xmit path * through RDS_IN_XMIT, and with connection management callbacks * via c_cm_lock. * * For receive callbacks, we rely on the underlying transport * (TCP, IB/RDMA) to provide the necessary synchronisation. */ struct workqueue_struct *rds_wq; EXPORT_SYMBOL_GPL(rds_wq); void rds_connect_path_complete(struct rds_conn_path *cp, int curr) { if (!rds_conn_path_transition(cp, curr, RDS_CONN_UP)) { printk(KERN_WARNING "%s: Cannot transition to state UP, " "current state is %d\n", __func__, atomic_read(&cp->cp_state)); rds_conn_path_drop(cp); return; } rdsdebug("conn %p for %pI4 to %pI4 complete\n", cp->cp_conn, &cp->cp_conn->c_laddr, &cp->cp_conn->c_faddr); cp->cp_reconnect_jiffies = 0; set_bit(0, &cp->cp_conn->c_map_queued); queue_delayed_work(rds_wq, &cp->cp_send_w, 0); queue_delayed_work(rds_wq, &cp->cp_recv_w, 0); } EXPORT_SYMBOL_GPL(rds_connect_path_complete); void rds_connect_complete(struct rds_connection *conn) { rds_connect_path_complete(&conn->c_path[0], RDS_CONN_CONNECTING); } EXPORT_SYMBOL_GPL(rds_connect_complete); /* * This random exponential backoff is relied on to eventually resolve racing * connects. * * If connect attempts race then both parties drop both connections and come * here to wait for a random amount of time before trying again. Eventually * the backoff range will be so much greater than the time it takes to * establish a connection that one of the pair will establish the connection * before the other's random delay fires. * * Connection attempts that arrive while a connection is already established * are also considered to be racing connects. This lets a connection from * a rebooted machine replace an existing stale connection before the transport * notices that the connection has failed. * * We should *always* start with a random backoff; otherwise a broken connection * will always take several iterations to be re-established. */ void rds_queue_reconnect(struct rds_conn_path *cp) { unsigned long rand; struct rds_connection *conn = cp->cp_conn; rdsdebug("conn %p for %pI4 to %pI4 reconnect jiffies %lu\n", conn, &conn->c_laddr, &conn->c_faddr, cp->cp_reconnect_jiffies); /* let peer with smaller addr initiate reconnect, to avoid duels */ if (conn->c_trans->t_type == RDS_TRANS_TCP && conn->c_laddr > conn->c_faddr) return; set_bit(RDS_RECONNECT_PENDING, &cp->cp_flags); if (cp->cp_reconnect_jiffies == 0) { cp->cp_reconnect_jiffies = rds_sysctl_reconnect_min_jiffies; queue_delayed_work(rds_wq, &cp->cp_conn_w, 0); return; } get_random_bytes(&rand, sizeof(rand)); rdsdebug("%lu delay %lu ceil conn %p for %pI4 -> %pI4\n", rand % cp->cp_reconnect_jiffies, cp->cp_reconnect_jiffies, conn, &conn->c_laddr, &conn->c_faddr); queue_delayed_work(rds_wq, &cp->cp_conn_w, rand % cp->cp_reconnect_jiffies); cp->cp_reconnect_jiffies = min(cp->cp_reconnect_jiffies * 2, rds_sysctl_reconnect_max_jiffies); } void rds_connect_worker(struct work_struct *work) { struct rds_conn_path *cp = container_of(work, struct rds_conn_path, cp_conn_w.work); struct rds_connection *conn = cp->cp_conn; int ret; if (cp->cp_index > 1 && cp->cp_conn->c_laddr > cp->cp_conn->c_faddr) return; clear_bit(RDS_RECONNECT_PENDING, &cp->cp_flags); ret = rds_conn_path_transition(cp, RDS_CONN_DOWN, RDS_CONN_CONNECTING); if (ret) { ret = conn->c_trans->conn_path_connect(cp); rdsdebug("conn %p for %pI4 to %pI4 dispatched, ret %d\n", conn, &conn->c_laddr, &conn->c_faddr, ret); if (ret) { if (rds_conn_path_transition(cp, RDS_CONN_CONNECTING, RDS_CONN_DOWN)) rds_queue_reconnect(cp); else rds_conn_path_error(cp, "connect failed\n"); } } } void rds_send_worker(struct work_struct *work) { struct rds_conn_path *cp = container_of(work, struct rds_conn_path, cp_send_w.work); int ret; if (rds_conn_path_state(cp) == RDS_CONN_UP) { clear_bit(RDS_LL_SEND_FULL, &cp->cp_flags); ret = rds_send_xmit(cp); cond_resched(); rdsdebug("conn %p ret %d\n", cp->cp_conn, ret); switch (ret) { case -EAGAIN: rds_stats_inc(s_send_immediate_retry); queue_delayed_work(rds_wq, &cp->cp_send_w, 0); break; case -ENOMEM: rds_stats_inc(s_send_delayed_retry); queue_delayed_work(rds_wq, &cp->cp_send_w, 2); default: break; } } } void rds_recv_worker(struct work_struct *work) { struct rds_conn_path *cp = container_of(work, struct rds_conn_path, cp_recv_w.work); int ret; if (rds_conn_path_state(cp) == RDS_CONN_UP) { ret = cp->cp_conn->c_trans->recv_path(cp); rdsdebug("conn %p ret %d\n", cp->cp_conn, ret); switch (ret) { case -EAGAIN: rds_stats_inc(s_recv_immediate_retry); queue_delayed_work(rds_wq, &cp->cp_recv_w, 0); break; case -ENOMEM: rds_stats_inc(s_recv_delayed_retry); queue_delayed_work(rds_wq, &cp->cp_recv_w, 2); default: break; } } } void rds_shutdown_worker(struct work_struct *work) { struct rds_conn_path *cp = container_of(work, struct rds_conn_path, cp_down_w); rds_conn_shutdown(cp); } void rds_threads_exit(void) { destroy_workqueue(rds_wq); } int rds_threads_init(void) { rds_wq = create_singlethread_workqueue("krdsd"); if (!rds_wq) return -ENOMEM; return 0; }