source: mainline/libc/generic/async.c@ 7f5b37a

/*
 * 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 async_futex = FUTEX_INITIALIZER;
static hash_table_t conn_hash_table;

typedef struct {
        pstid_t ptid;                /**< Thread waiting for this message */
        int active;                  /**< If this thread is currently active */
        int done;                    /**< If reply was received */
        ipc_call_t *dataptr;         /**< Pointer where the answer data
                                      *   should be stored */
        ipcarg_t retval;
} amsg_t;

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(&async_futex);

        key = call->in_phone_hash;
        hlp = hash_table_find(&conn_hash_table, &key);
        if (!hlp) {
                futex_up(&async_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(&async_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(&async_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(&async_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(&async_futex);
        key = conn->in_phone_hash;
        hash_table_remove(&conn_hash_table, &key, 1);
        futex_up(&async_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(&async_futex);
        /* Add connection to hash table */
        hash_table_insert(&conn_hash_table, &key, &conn->link);
        futex_up(&async_futex);

        psthread_add_ready(conn->ptid);

        return conn->ptid;
}

/** Handle call that was received */
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(&async_futex); /* async_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(&async_futex); /* async_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;
        }
        
}

/** IPC handler for messages in async framework
 *
 * Notify thread that is waiting for this message, that it arrived
 */
static void reply_received(void *private, int retval,
                           ipc_call_t *data)
{
        amsg_t *msg = (amsg_t *) private;

        msg->retval = retval;

        futex_down(&async_futex);
        /* Copy data after futex_down, just in case the
         * call was detached 
         */
        if (msg->dataptr)
                *msg->dataptr = *data; 
        
        msg->done = 1;
        if (! msg->active) {
                msg->active = 1;
                psthread_add_ready(msg->ptid);
        }
        futex_up(&async_futex);
}

/** Send message and return id of the sent message
 *
 * The return value can be used as input for async_wait() to wait
 * for completion.
 */
aid_t async_send_2(int phoneid, ipcarg_t method, ipcarg_t arg1, ipcarg_t arg2,
                   ipc_call_t *dataptr)
{
        amsg_t *msg;

        msg = malloc(sizeof(*msg));
        msg->active = 1;
        msg->done = 0;
        msg->dataptr = dataptr;
        ipc_call_async_2(phoneid,method,arg1,arg2,msg,reply_received);

        return (aid_t) msg;
}

/** Wait for a message sent by async framework
 *
 * @param amsgid Message ID to wait for
 * @param retval Pointer to variable where will be stored retval
 *               of the answered message. If NULL, it is ignored.
 *
 */
void async_wait_for(aid_t amsgid, ipcarg_t *retval)
{
        amsg_t *msg = (amsg_t *) amsgid;
        connection_t *conn;

        futex_down(&async_futex);
        if (msg->done) {
                futex_up(&async_futex);
                goto done;
        }

        msg->ptid = psthread_get_id();
        msg->active = 0;
        /* Leave locked async_futex when entering this function */
        psthread_schedule_next_adv(PS_TO_MANAGER);
        /* futex is up automatically after psthread_schedule_next...*/
done:
        if (retval)
                *retval = msg->retval;
        free(msg);
}