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- /*
- * 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_complete(struct rds_connection *conn)
- {
- if (!rds_conn_transition(conn, RDS_CONN_CONNECTING, RDS_CONN_UP)) {
- printk(KERN_WARNING "%s: Cannot transition to state UP, "
- "current state is %d\n",
- __func__,
- atomic_read(&conn->c_state));
- rds_conn_drop(conn);
- return;
- }
- rdsdebug("conn %p for %pI4 to %pI4 complete\n",
- conn, &conn->c_laddr, &conn->c_faddr);
- conn->c_reconnect_jiffies = 0;
- set_bit(0, &conn->c_map_queued);
- queue_delayed_work(rds_wq, &conn->c_send_w, 0);
- queue_delayed_work(rds_wq, &conn->c_recv_w, 0);
- }
- 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_connection *conn)
- {
- unsigned long rand;
- rdsdebug("conn %p for %pI4 to %pI4 reconnect jiffies %lu\n",
- conn, &conn->c_laddr, &conn->c_faddr,
- conn->c_reconnect_jiffies);
- set_bit(RDS_RECONNECT_PENDING, &conn->c_flags);
- if (conn->c_reconnect_jiffies == 0) {
- conn->c_reconnect_jiffies = rds_sysctl_reconnect_min_jiffies;
- queue_delayed_work(rds_wq, &conn->c_conn_w, 0);
- return;
- }
- get_random_bytes(&rand, sizeof(rand));
- rdsdebug("%lu delay %lu ceil conn %p for %pI4 -> %pI4\n",
- rand % conn->c_reconnect_jiffies, conn->c_reconnect_jiffies,
- conn, &conn->c_laddr, &conn->c_faddr);
- queue_delayed_work(rds_wq, &conn->c_conn_w,
- rand % conn->c_reconnect_jiffies);
- conn->c_reconnect_jiffies = min(conn->c_reconnect_jiffies * 2,
- rds_sysctl_reconnect_max_jiffies);
- }
- void rds_connect_worker(struct work_struct *work)
- {
- struct rds_connection *conn = container_of(work, struct rds_connection, c_conn_w.work);
- int ret;
- clear_bit(RDS_RECONNECT_PENDING, &conn->c_flags);
- if (rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_CONNECTING)) {
- ret = conn->c_trans->conn_connect(conn);
- rdsdebug("conn %p for %pI4 to %pI4 dispatched, ret %d\n",
- conn, &conn->c_laddr, &conn->c_faddr, ret);
- if (ret) {
- if (rds_conn_transition(conn, RDS_CONN_CONNECTING, RDS_CONN_DOWN))
- rds_queue_reconnect(conn);
- else
- rds_conn_error(conn, "RDS: connect failed\n");
- }
- }
- }
- void rds_send_worker(struct work_struct *work)
- {
- struct rds_connection *conn = container_of(work, struct rds_connection, c_send_w.work);
- int ret;
- if (rds_conn_state(conn) == RDS_CONN_UP) {
- clear_bit(RDS_LL_SEND_FULL, &conn->c_flags);
- ret = rds_send_xmit(conn);
- cond_resched();
- rdsdebug("conn %p ret %d\n", conn, ret);
- switch (ret) {
- case -EAGAIN:
- rds_stats_inc(s_send_immediate_retry);
- queue_delayed_work(rds_wq, &conn->c_send_w, 0);
- break;
- case -ENOMEM:
- rds_stats_inc(s_send_delayed_retry);
- queue_delayed_work(rds_wq, &conn->c_send_w, 2);
- default:
- break;
- }
- }
- }
- void rds_recv_worker(struct work_struct *work)
- {
- struct rds_connection *conn = container_of(work, struct rds_connection, c_recv_w.work);
- int ret;
- if (rds_conn_state(conn) == RDS_CONN_UP) {
- ret = conn->c_trans->recv(conn);
- rdsdebug("conn %p ret %d\n", conn, ret);
- switch (ret) {
- case -EAGAIN:
- rds_stats_inc(s_recv_immediate_retry);
- queue_delayed_work(rds_wq, &conn->c_recv_w, 0);
- break;
- case -ENOMEM:
- rds_stats_inc(s_recv_delayed_retry);
- queue_delayed_work(rds_wq, &conn->c_recv_w, 2);
- default:
- break;
- }
- }
- }
- void rds_shutdown_worker(struct work_struct *work)
- {
- struct rds_connection *conn = container_of(work, struct rds_connection, c_down_w);
- rds_conn_shutdown(conn);
- }
- 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;
- }
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