diff options
Diffstat (limited to 'net/rds/threads.c')
| -rw-r--r-- | net/rds/threads.c | 265 |
1 files changed, 265 insertions, 0 deletions
diff --git a/net/rds/threads.c b/net/rds/threads.c new file mode 100644 index 000000000000..828a1bf9ea92 --- /dev/null +++ b/net/rds/threads.c @@ -0,0 +1,265 @@ +/* + * 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 "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 c_send_lock, 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; + +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)); + atomic_set(&conn->c_state, RDS_CONN_ERROR); + queue_work(rds_wq, &conn->c_down_w); + 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); +} + +/* + * 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. + */ +static 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_shutdown_worker(struct work_struct *work) +{ + struct rds_connection *conn = container_of(work, struct rds_connection, c_down_w); + + /* shut it down unless it's down already */ + if (!rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_DOWN)) { + /* + * Quiesce the connection mgmt handlers before we start tearing + * things down. We don't hold the mutex for the entire + * duration of the shutdown operation, else we may be + * deadlocking with the CM handler. Instead, the CM event + * handler is supposed to check for state DISCONNECTING + */ + mutex_lock(&conn->c_cm_lock); + if (!rds_conn_transition(conn, RDS_CONN_UP, RDS_CONN_DISCONNECTING) + && !rds_conn_transition(conn, RDS_CONN_ERROR, RDS_CONN_DISCONNECTING)) { + rds_conn_error(conn, "shutdown called in state %d\n", + atomic_read(&conn->c_state)); + mutex_unlock(&conn->c_cm_lock); + return; + } + mutex_unlock(&conn->c_cm_lock); + + mutex_lock(&conn->c_send_lock); + conn->c_trans->conn_shutdown(conn); + rds_conn_reset(conn); + mutex_unlock(&conn->c_send_lock); + + if (!rds_conn_transition(conn, RDS_CONN_DISCONNECTING, RDS_CONN_DOWN)) { + /* This can happen - eg when we're in the middle of tearing + * down the connection, and someone unloads the rds module. + * Quite reproduceable with loopback connections. + * Mostly harmless. + */ + rds_conn_error(conn, + "%s: failed to transition to state DOWN, " + "current state is %d\n", + __func__, + atomic_read(&conn->c_state)); + return; + } + } + + /* Then reconnect if it's still live. + * The passive side of an IB loopback connection is never added + * to the conn hash, so we never trigger a reconnect on this + * conn - the reconnect is always triggered by the active peer. */ + cancel_delayed_work(&conn->c_conn_w); + if (!hlist_unhashed(&conn->c_hash_node)) + rds_queue_reconnect(conn); +} + +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) { + ret = rds_send_xmit(conn); + 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_threads_exit(void) +{ + destroy_workqueue(rds_wq); +} + +int __init rds_threads_init(void) +{ + rds_wq = create_singlethread_workqueue("krdsd"); + if (rds_wq == NULL) + return -ENOMEM; + + return 0; +} |