266 lines
8.5 KiB
C
266 lines
8.5 KiB
C
/*
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* Copyright (c) 2006 Oracle. All rights reserved.
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*
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* This software is available to you under a choice of one of two
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* licenses. You may choose to be licensed under the terms of the GNU
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* General Public License (GPL) Version 2, available from the file
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* COPYING in the main directory of this source tree, or the
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* OpenIB.org BSD license below:
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*
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* Redistribution and use in source and binary forms, with or
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* without modification, are permitted provided that the following
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* conditions are met:
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*
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* - Redistributions of source code must retain the above
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* copyright notice, this list of conditions and the following
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* disclaimer.
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*
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* - Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials
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* provided with the distribution.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*
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*/
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#include <linux/kernel.h>
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#include <linux/random.h>
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#include "rds.h"
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/*
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* All of connection management is simplified by serializing it through
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* work queues that execute in a connection managing thread.
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*
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* TCP wants to send acks through sendpage() in response to data_ready(),
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* but it needs a process context to do so.
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*
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* The receive paths need to allocate but can't drop packets (!) so we have
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* a thread around to block allocating if the receive fast path sees an
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* allocation failure.
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*/
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/* Grand Unified Theory of connection life cycle:
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* At any point in time, the connection can be in one of these states:
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* DOWN, CONNECTING, UP, DISCONNECTING, ERROR
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*
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* The following transitions are possible:
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* ANY -> ERROR
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* UP -> DISCONNECTING
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* ERROR -> DISCONNECTING
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* DISCONNECTING -> DOWN
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* DOWN -> CONNECTING
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* CONNECTING -> UP
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*
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* Transition to state DISCONNECTING/DOWN:
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* - Inside the shutdown worker; synchronizes with xmit path
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* through c_send_lock, and with connection management callbacks
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* via c_cm_lock.
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*
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* For receive callbacks, we rely on the underlying transport
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* (TCP, IB/RDMA) to provide the necessary synchronisation.
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*/
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struct workqueue_struct *rds_wq;
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void rds_connect_complete(struct rds_connection *conn)
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{
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if (!rds_conn_transition(conn, RDS_CONN_CONNECTING, RDS_CONN_UP)) {
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printk(KERN_WARNING "%s: Cannot transition to state UP, "
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"current state is %d\n",
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__func__,
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atomic_read(&conn->c_state));
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atomic_set(&conn->c_state, RDS_CONN_ERROR);
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queue_work(rds_wq, &conn->c_down_w);
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return;
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}
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rdsdebug("conn %p for %pI4 to %pI4 complete\n",
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conn, &conn->c_laddr, &conn->c_faddr);
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conn->c_reconnect_jiffies = 0;
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set_bit(0, &conn->c_map_queued);
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queue_delayed_work(rds_wq, &conn->c_send_w, 0);
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queue_delayed_work(rds_wq, &conn->c_recv_w, 0);
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}
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/*
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* This random exponential backoff is relied on to eventually resolve racing
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* connects.
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*
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* If connect attempts race then both parties drop both connections and come
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* here to wait for a random amount of time before trying again. Eventually
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* the backoff range will be so much greater than the time it takes to
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* establish a connection that one of the pair will establish the connection
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* before the other's random delay fires.
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*
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* Connection attempts that arrive while a connection is already established
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* are also considered to be racing connects. This lets a connection from
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* a rebooted machine replace an existing stale connection before the transport
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* notices that the connection has failed.
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*
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* We should *always* start with a random backoff; otherwise a broken connection
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* will always take several iterations to be re-established.
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*/
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static void rds_queue_reconnect(struct rds_connection *conn)
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{
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unsigned long rand;
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rdsdebug("conn %p for %pI4 to %pI4 reconnect jiffies %lu\n",
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conn, &conn->c_laddr, &conn->c_faddr,
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conn->c_reconnect_jiffies);
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set_bit(RDS_RECONNECT_PENDING, &conn->c_flags);
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if (conn->c_reconnect_jiffies == 0) {
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conn->c_reconnect_jiffies = rds_sysctl_reconnect_min_jiffies;
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queue_delayed_work(rds_wq, &conn->c_conn_w, 0);
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return;
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}
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get_random_bytes(&rand, sizeof(rand));
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rdsdebug("%lu delay %lu ceil conn %p for %pI4 -> %pI4\n",
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rand % conn->c_reconnect_jiffies, conn->c_reconnect_jiffies,
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conn, &conn->c_laddr, &conn->c_faddr);
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queue_delayed_work(rds_wq, &conn->c_conn_w,
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rand % conn->c_reconnect_jiffies);
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conn->c_reconnect_jiffies = min(conn->c_reconnect_jiffies * 2,
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rds_sysctl_reconnect_max_jiffies);
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}
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void rds_connect_worker(struct work_struct *work)
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{
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struct rds_connection *conn = container_of(work, struct rds_connection, c_conn_w.work);
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int ret;
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clear_bit(RDS_RECONNECT_PENDING, &conn->c_flags);
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if (rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_CONNECTING)) {
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ret = conn->c_trans->conn_connect(conn);
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rdsdebug("conn %p for %pI4 to %pI4 dispatched, ret %d\n",
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conn, &conn->c_laddr, &conn->c_faddr, ret);
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if (ret) {
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if (rds_conn_transition(conn, RDS_CONN_CONNECTING, RDS_CONN_DOWN))
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rds_queue_reconnect(conn);
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else
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rds_conn_error(conn, "RDS: connect failed\n");
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}
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}
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}
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void rds_shutdown_worker(struct work_struct *work)
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{
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struct rds_connection *conn = container_of(work, struct rds_connection, c_down_w);
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/* shut it down unless it's down already */
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if (!rds_conn_transition(conn, RDS_CONN_DOWN, RDS_CONN_DOWN)) {
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/*
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* Quiesce the connection mgmt handlers before we start tearing
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* things down. We don't hold the mutex for the entire
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* duration of the shutdown operation, else we may be
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* deadlocking with the CM handler. Instead, the CM event
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* handler is supposed to check for state DISCONNECTING
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*/
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mutex_lock(&conn->c_cm_lock);
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if (!rds_conn_transition(conn, RDS_CONN_UP, RDS_CONN_DISCONNECTING)
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&& !rds_conn_transition(conn, RDS_CONN_ERROR, RDS_CONN_DISCONNECTING)) {
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rds_conn_error(conn, "shutdown called in state %d\n",
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atomic_read(&conn->c_state));
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mutex_unlock(&conn->c_cm_lock);
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return;
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}
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mutex_unlock(&conn->c_cm_lock);
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mutex_lock(&conn->c_send_lock);
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conn->c_trans->conn_shutdown(conn);
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rds_conn_reset(conn);
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mutex_unlock(&conn->c_send_lock);
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if (!rds_conn_transition(conn, RDS_CONN_DISCONNECTING, RDS_CONN_DOWN)) {
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/* This can happen - eg when we're in the middle of tearing
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* down the connection, and someone unloads the rds module.
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* Quite reproduceable with loopback connections.
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* Mostly harmless.
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*/
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rds_conn_error(conn,
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"%s: failed to transition to state DOWN, "
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"current state is %d\n",
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__func__,
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atomic_read(&conn->c_state));
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return;
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}
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}
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/* Then reconnect if it's still live.
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* The passive side of an IB loopback connection is never added
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* to the conn hash, so we never trigger a reconnect on this
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* conn - the reconnect is always triggered by the active peer. */
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cancel_delayed_work(&conn->c_conn_w);
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if (!hlist_unhashed(&conn->c_hash_node))
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rds_queue_reconnect(conn);
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}
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void rds_send_worker(struct work_struct *work)
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{
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struct rds_connection *conn = container_of(work, struct rds_connection, c_send_w.work);
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int ret;
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if (rds_conn_state(conn) == RDS_CONN_UP) {
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ret = rds_send_xmit(conn);
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rdsdebug("conn %p ret %d\n", conn, ret);
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switch (ret) {
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case -EAGAIN:
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rds_stats_inc(s_send_immediate_retry);
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queue_delayed_work(rds_wq, &conn->c_send_w, 0);
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break;
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case -ENOMEM:
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rds_stats_inc(s_send_delayed_retry);
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queue_delayed_work(rds_wq, &conn->c_send_w, 2);
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default:
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break;
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}
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}
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}
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void rds_recv_worker(struct work_struct *work)
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{
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struct rds_connection *conn = container_of(work, struct rds_connection, c_recv_w.work);
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int ret;
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if (rds_conn_state(conn) == RDS_CONN_UP) {
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ret = conn->c_trans->recv(conn);
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rdsdebug("conn %p ret %d\n", conn, ret);
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switch (ret) {
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case -EAGAIN:
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rds_stats_inc(s_recv_immediate_retry);
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queue_delayed_work(rds_wq, &conn->c_recv_w, 0);
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break;
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case -ENOMEM:
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rds_stats_inc(s_recv_delayed_retry);
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queue_delayed_work(rds_wq, &conn->c_recv_w, 2);
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default:
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break;
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}
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}
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}
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void rds_threads_exit(void)
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{
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destroy_workqueue(rds_wq);
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}
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int __init rds_threads_init(void)
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{
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rds_wq = create_singlethread_workqueue("krdsd");
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if (rds_wq == NULL)
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return -ENOMEM;
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return 0;
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}
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