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-rw-r--r--net/rds/threads.c265
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diff --git a/net/rds/threads.c b/net/rds/threads.c
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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 "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;
+}
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