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/*

 * Copyright (C) 2006 Ondrej Palkovsky

 * All rights reserved.

 *

 * 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 name of the author may not be used to endorse or promote products

 *   derived from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.

 */ 

/**

 * Asynchronous library

 *

 * The aim of this library is facilitating writing programs utilizing 

 * the asynchronous nature of Helenos IPC, yet using a normal way

 * of programming. 

 *

 * You should be able to write very simple multithreaded programs, 

 * the async framework will automatically take care of most synchronization

 * problems.

 *

 * Default semantics:

 * - send() - send asynchronously. If the kernel refuses to send more

 *            messages, [ try to get responses from kernel, if nothing

 *            found, might try synchronous ]

 *

 * Example of use:

 * 

 * 1) Multithreaded client application

 *  create_thread(thread1);

 *  create_thread(thread2);

 *  ...

 *  

 *  thread1() {

 *        conn = ipc_connect_me_to();

 *        c1 = send(conn);

 *        c2 = send(conn);

 *        wait_for(c1);

 *        wait_for(c2);

 *  }

 *

 *

 * 2) Multithreaded server application

 * main() {

 *      async_manager();

 * }

 * 

 *

 * client_connection(icallid, *icall) {

 *       if (want_refuse) {

 *           ipc_answer_fast(icallid, ELIMIT, 0, 0);

 *           return;

 *       }

 *       ipc_answer_fast(icallid, 0, 0, 0);

 *

 *       callid = async_get_call(&call);

 *       handle(callid, call);

 *       ipc_answer_fast(callid, 1,2,3);

 *

 *       callid = async_get_call(&call);

 *       ....

 * }

 *

 * TODO: Detaching/joining dead psthreads?

 */

#include <futex.h>

#include <async.h>

#include <psthread.h>

#include <stdio.h>

#include <libadt/hash_table.h>

#include <libadt/list.h>

#include <ipc/ipc.h>

#include <assert.h>

#include <errno.h>

static atomic_t conn_futex = FUTEX_INITIALIZER;

static hash_table_t conn_hash_table;

typedef struct {

	link_t link;

	ipc_callid_t callid;

	ipc_call_t call;

} msg_t;

typedef struct {

	link_t link;

	ipcarg_t in_phone_hash;		/**< Incoming phone hash. */

	link_t msg_queue;              /**< Messages that should be delivered to this thread */

	pstid_t ptid;                /**< Thread associated with this connection */

	int active;                     /**< If this thread is currently active */

	/* Structures for connection opening packet */

	ipc_callid_t callid;

	ipc_call_t call;

	void (*cthread)(ipc_callid_t,ipc_call_t *);

} connection_t;

__thread connection_t *PS_connection;

/* Hash table functions */

#define CONN_HASH_TABLE_CHAINS	32

static hash_index_t conn_hash(unsigned long *key)

{

	assert(key);

	return ((*key) >> 4) % CONN_HASH_TABLE_CHAINS;

}

static int conn_compare(unsigned long key[], hash_count_t keys, link_t *item)

{

	connection_t *hs;

	hs = hash_table_get_instance(item, connection_t, link);

	return key[0] == hs->in_phone_hash;

}

static void conn_remove(link_t *item)

{

	free(hash_table_get_instance(item, connection_t, link));

}

/** Operations for NS hash table. */

static hash_table_operations_t conn_hash_table_ops = {

	.hash = conn_hash,

	.compare = conn_compare,

	.remove_callback = conn_remove

};

/** Try to route a call to an appropriate connection thread

 *

 */

static int route_call(ipc_callid_t callid, ipc_call_t *call)

{

	connection_t *conn;

	msg_t *msg;

	link_t *hlp;

	unsigned long key;

	futex_down(&conn_futex);

	key = call->in_phone_hash;

	hlp = hash_table_find(&conn_hash_table, &key);

	if (!hlp) {

		futex_up(&conn_futex);

		return 0;

	}

	conn = hash_table_get_instance(hlp, connection_t, link);

	msg = malloc(sizeof(*msg));

	msg->callid = callid;

	msg->call = *call;

	list_append(&msg->link, &conn->msg_queue);

	if (!conn->active) {

		conn->active = 1;

		psthread_add_ready(conn->ptid);

	}

	futex_up(&conn_futex);

	return 1;

}

/** Return new incoming message for current(thread-local) connection */

ipc_callid_t async_get_call(ipc_call_t *call)

{

	msg_t *msg;

	ipc_callid_t callid;

	connection_t *conn;

	futex_down(&conn_futex);

	conn = PS_connection;

	/* If nothing in queue, wait until something appears */

	if (list_empty(&conn->msg_queue)) {

		conn->active = 0;

		psthread_schedule_next_adv(PS_TO_MANAGER);

	}

	msg = list_get_instance(conn->msg_queue.next, msg_t, link);

	list_remove(&msg->link);

	callid = msg->callid;

	*call = msg->call;

	free(msg);

	futex_up(&conn_futex);

	return callid;

}

/** Thread function that gets created on new connection

 *

 * This function is defined as a weak symbol - to be redefined in

 * user code.

 */

void client_connection(ipc_callid_t callid, ipc_call_t *call)

{

	ipc_answer_fast(callid, ENOENT, 0, 0);

}

/** Wrapper for client connection thread

 *

 * When new connection arrives, thread with this function is created.

 * It calls client_connection and does final cleanup.

 *

 * @parameter arg Connection structure pointer

 */

static int connection_thread(void  *arg)

{

	unsigned long key;

	msg_t *msg;

	connection_t *conn;

	/* Setup thread local connection pointer */

	PS_connection = (connection_t *)arg;

	conn = PS_connection;

	conn->cthread(conn->callid, &conn->call);

	/* Remove myself from connection hash table */

	futex_down(&conn_futex);

	key = conn->in_phone_hash;

	hash_table_remove(&conn_hash_table, &key, 1);

	futex_up(&conn_futex);

	/* Answer all remaining messages with ehangup */

	while (!list_empty(&conn->msg_queue)) {

		msg = list_get_instance(conn->msg_queue.next, msg_t, link);

		list_remove(&msg->link);

		ipc_answer_fast(msg->callid, EHANGUP, 0, 0);

		free(msg);

	}

}

/** Create new thread for a new connection 

 *

 * Creates new thread for connection, fills in connection

 * structures and inserts it into the hash table, so that

 * later we can easily do routing of messages to particular

 * threads.

 *

 * @param callid Callid of the IPC_M_CONNECT_ME_TO packet

 * @param call Call data of the opening packet

 * @param cthread Thread function that should be called upon

 *                opening the connection

 * @return New thread id

 */

pstid_t async_new_connection(ipc_callid_t callid, ipc_call_t *call,

			     void (*cthread)(ipc_callid_t,ipc_call_t *))

{

	pstid_t ptid;

	connection_t *conn;

	unsigned long key;

	conn = malloc(sizeof(*conn));

	if (!conn) {

		ipc_answer_fast(callid, ENOMEM, 0, 0);

		return NULL;

	}

	conn->in_phone_hash = IPC_GET_ARG3(*call);

	list_initialize(&conn->msg_queue);

	conn->ptid = psthread_create(connection_thread, conn);

	conn->callid = callid;

	conn->call = *call;

	conn->active = 1; /* We will activate it asap */

	conn->cthread = cthread;

	list_initialize(&conn->link);

	if (!conn->ptid) {

		free(conn);

		ipc_answer_fast(callid, ENOMEM, 0, 0);

		return NULL;

	}

	key = conn->in_phone_hash;

	futex_down(&conn_futex);

	/* Add connection to hash table */

	hash_table_insert(&conn_hash_table, &key, &conn->link);

	futex_up(&conn_futex);

	psthread_add_ready(conn->ptid);

	return conn->ptid;

}

/** Handle call to a task */

static void handle_call(ipc_callid_t callid, ipc_call_t *call)

{

	if (route_call(callid, call))

		return;

	switch (IPC_GET_METHOD(*call)) {

	case IPC_M_INTERRUPT:

		break;

	case IPC_M_CONNECT_ME_TO:

		/* Open new connection with thread etc. */

		async_new_connection(callid, call, client_connection);

		break;

	default:

		ipc_answer_fast(callid, EHANGUP, 0, 0);

	}

}

/** Endless loop dispatching incoming calls and answers */

int async_manager()

{

	ipc_call_t call;

	ipc_callid_t callid;

	while (1) {

		if (psthread_schedule_next_adv(PS_FROM_MANAGER)) {

			futex_up(&conn_futex); /* conn_futex is always held

						* when entering manager thread

						*/

			continue;

		}

		callid = ipc_wait_cycle(&call,SYNCH_NO_TIMEOUT,SYNCH_BLOCKING);

		if (callid & IPC_CALLID_ANSWERED)

			continue;

		handle_call(callid, &call);

	}

}

/** Function to start async_manager as a standalone thread 

 * 

 * When more kernel threads are used, one async manager should

 * exist per thread. The particular implementation may change,

 * currently one async_manager is started automatically per kernel

 * thread except main thread. 

 */

static int async_manager_thread(void *arg)

{

	futex_up(&conn_futex); /* conn_futex is always locked when entering

				* manager */

	async_manager();

}

/** Add one manager to manager list */

void async_create_manager(void)

{

	pstid_t ptid;

	ptid = psthread_create(async_manager_thread, NULL);

	psthread_add_manager(ptid);

}

/** Remove one manager from manager list */

void async_destroy_manager(void)

{

	psthread_remove_manager();

}

/** Initialize internal structures needed for async manager */

int _async_init(void)

{

	if (!hash_table_create(&conn_hash_table, CONN_HASH_TABLE_CHAINS, 1, &conn_hash_table_ops)) {

		printf("%s: cannot create hash table\n", "async");

		return ENOMEM;

	}

}