tipc: introduce new TIPC server infrastructure

TIPC has two internal servers, one providing a subscription
service for topology events, and another providing the
configuration interface. These servers have previously been running
in BH context, accessing the TIPC-port (aka native) API directly.
Apart from these servers, even the TIPC socket implementation is
partially built on this API.

As this API may simultaneously be called via different paths and in
different contexts, a complex and costly lock policiy is required
in order to protect TIPC internal resources.

To eliminate the need for this complex lock policiy, we introduce
a new, generic service API that uses kernel sockets for message
passing instead of the native API. Once the toplogy and configuration
servers are converted to use this new service, all code pertaining
to the native API can be removed. This entails a significant
reduction in code amount and complexity, and opens up for a complete
rework of the locking policy in TIPC.

The new service also solves another problem:

As the current topology server works in BH context, it cannot easily
be blocked when sending of events fails due to congestion. In such
cases events may have to be silently dropped, something that is
unacceptable. Therefore, the new service keeps a dedicated outbound
queue receiving messages from BH context. Once messages are
inserted into this queue, we will immediately schedule a work from a
special workqueue. This way, messages/events from the topology server
are in reality sent in process context, and the server can block
if necessary.

Analogously, there is a new workqueue for receiving messages. Once a
notification about an arriving message is received in BH context, we
schedule a work from the receive workqueue to do the job of
receiving the message in process context.

As both sending and receive messages are now finished in processes,
subscribed events cannot be dropped any more.

As of this commit, this new server infrastructure is built, but
not actually yet called by the existing TIPC code, but since the
conversion changes required in order to use it are significant,
the addition is kept here as a separate commit.

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 94 insertions, 0 deletions

diff --git a/net/tipc/server.h b/net/tipc/server.h
new file mode 100644
index 000000000000..98b23f20bc0f
--- /dev/null
+++ b/net/tipc/server.h
@@ -0,0 +1,94 @@
+/*
+ * net/tipc/server.h: Include file for TIPC server code
+ *
+ * Copyright (c) 2012-2013, Wind River Systems
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. 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.
+ * 3. Neither the names of the copyright holders nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * Alternatively, this software may be distributed under the terms of the
+ * GNU General Public License ("GPL") version 2 as published by the Free
+ * Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _TIPC_SERVER_H
+#define _TIPC_SERVER_H
+
+#include "core.h"
+
+#define TIPC_SERVER_NAME_LEN    32
+
+/**
+ * struct tipc_server - TIPC server structure
+ * @conn_idr: identifier set of connection
+ * @idr_lock: protect the connection identifier set
+ * @idr_in_use: amount of allocated identifier entry
+ * @rcvbuf_cache: memory cache of server receive buffer
+ * @rcv_wq: receive workqueue
+ * @send_wq: send workqueue
+ * @max_rcvbuf_size: maximum permitted receive message length
+ * @tipc_conn_new: callback will be called when new connection is incoming
+ * @tipc_conn_shutdown: callback will be called when connection is shut down
+ * @tipc_conn_recvmsg: callback will be called when message arrives
+ * @saddr: TIPC server address
+ * @name: server name
+ * @imp: message importance
+ * @type: socket type
+ * @enabled: identify whether server is launched or not
+ */
+struct tipc_server {
+        struct idr conn_idr;
+        spinlock_t idr_lock;
+        int idr_in_use;
+        struct kmem_cache *rcvbuf_cache;
+        struct workqueue_struct *rcv_wq;
+        struct workqueue_struct *send_wq;
+        int max_rcvbuf_size;
+        void *(*tipc_conn_new) (int conid);
+        void (*tipc_conn_shutdown) (int conid, void *usr_data);
+        void (*tipc_conn_recvmsg) (int conid, struct sockaddr_tipc *addr,
+                                   void *usr_data, void *buf, size_t len);
+        struct sockaddr_tipc *saddr;
+        const char name[TIPC_SERVER_NAME_LEN];
+        int imp;
+        int type;
+        int enabled;
+};
+
+int tipc_conn_sendmsg(struct tipc_server *s, int conid,
+                      struct sockaddr_tipc *addr, void *data, size_t len);
+
+/**
+ * tipc_conn_terminate - terminate connection with server
+ *
+ * Note: Must call it in process context since it might sleep
+ */
+void tipc_conn_terminate(struct tipc_server *s, int conid);
+
+int tipc_server_start(struct tipc_server *s);
+
+void tipc_server_stop(struct tipc_server *s);
+
+#endif