source: mainline/uspace/lib/libc/generic/async.c@ f5b4fb9

/*
 * 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.
 */

/** @addtogroup libc
 * @{
 */
/** @file
 */ 

/**
 * 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:
 * - async_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 (pseudo C):
 * 
 * 1) Multithreaded client application
 *
 * fibril_create(fibril1, ...);
 * fibril_create(fibril2, ...);
 * ...
 *  
 * int fibril1(void *arg)
 * {
 *      conn = ipc_connect_me_to();
 *      c1 = async_send(conn);
 *      c2 = async_send(conn);
 *      async_wait_for(c1);
 *      async_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, EOK, 0, 0);
 *
 *      callid = async_get_call(&call);
 *      handle_call(callid, call);
 *      ipc_answer_fast(callid, 1, 2, 3);
 *
 *      callid = async_get_call(&call);
 *      ....
 * }
 *
 */

#include <futex.h>
#include <async.h>
#include <fibril.h>
#include <stdio.h>
#include <libadt/hash_table.h>
#include <libadt/list.h>
#include <ipc/ipc.h>
#include <assert.h>
#include <errno.h>
#include <sys/time.h>
#include <arch/barrier.h>

atomic_t async_futex = FUTEX_INITIALIZER;
static hash_table_t conn_hash_table;
static LIST_INITIALIZE(timeout_list);

/** Structures of this type represent a waiting fibril. */
typedef struct {
        /** Expiration time. */
        struct timeval expires;         
        /** If true, this struct is in the timeout list. */
        int inlist;
        /** Timeout list link. */
        link_t link;

        /** Fibril waiting for this message. */
        fid_t fid;
        /** If true, this fibril is currently active. */
        int active;
        /** If true, we have timed out. */
        int timedout;
} awaiter_t;

typedef struct {
        awaiter_t wdata;
        
        /** If reply was received. */
        int done;
        /** Pointer to where the answer data is stored. */
        ipc_call_t *dataptr;

        ipcarg_t retval;
} amsg_t;

typedef struct {
        link_t link;
        ipc_callid_t callid;
        ipc_call_t call;
} msg_t;

typedef struct {
        awaiter_t wdata;

        /** Hash table link. */
        link_t link;

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

        /** Messages that should be delivered to this fibril. */
        link_t msg_queue;               
                                         
        /** Identification of the opening call. */
        ipc_callid_t callid;
        /** Call data of the opening call. */
        ipc_call_t call;

        /** Identification of the closing call. */
        ipc_callid_t close_callid;

        /** Fibril function that will be used to handle the connection. */
        void (*cfibril)(ipc_callid_t, ipc_call_t *);
} connection_t;

/** Identifier of the incoming connection handled by the current fibril. */
__thread connection_t *FIBRIL_connection;

/** If true, it is forbidden to use async_req functions and all preemption is
 * disabled. */
__thread int in_interrupt_handler;

static void default_client_connection(ipc_callid_t callid, ipc_call_t *call);
static void default_interrupt_received(ipc_callid_t callid, ipc_call_t *call);
static async_client_conn_t client_connection = default_client_connection;
static async_client_conn_t interrupt_received = default_interrupt_received;

#define CONN_HASH_TABLE_CHAINS  32

/** Compute hash into the connection hash table based on the source phone hash.
 *
 * @param key           Pointer to source phone hash.
 *
 * @return              Index into the connection hash table.
 */
static hash_index_t conn_hash(unsigned long *key)
{
        assert(key);
        return ((*key) >> 4) % CONN_HASH_TABLE_CHAINS;
}

/** Compare hash table item with a key.
 *
 * @param key           Array containing the source phone hash as the only item.
 * @param keys          Expected 1 but ignored.
 * @param item          Connection hash table item.
 *
 * @return              True on match, false otherwise.
 */
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;
}

/** Connection hash table removal callback function.
 *
 * This function is called whenever a connection is removed from the connection
 * hash table.
 *
 * @param item          Connection hash table item being removed.
 */
static void conn_remove(link_t *item)
{
        free(hash_table_get_instance(item, connection_t, link));
}


/** Operations for the connection hash table. */
static hash_table_operations_t conn_hash_table_ops = {
        .hash = conn_hash,
        .compare = conn_compare,
        .remove_callback = conn_remove
};

/** Sort in current fibril's timeout request.
 *
 * @param wd            Wait data of the current fibril.
 */
static void insert_timeout(awaiter_t *wd)
{
        link_t *tmp;
        awaiter_t *cur;

        wd->timedout = 0;
        wd->inlist = 1;

        tmp = timeout_list.next;
        while (tmp != &timeout_list) {
                cur = list_get_instance(tmp, awaiter_t, link);
                if (tv_gteq(&cur->expires, &wd->expires))
                        break;
                tmp = tmp->next;
        }
        list_append(&wd->link, tmp);
}

/** Try to route a call to an appropriate connection fibril.
 *
 */
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 (IPC_GET_METHOD(*call) == IPC_M_PHONE_HUNGUP)
                conn->close_callid = callid;
        
        /* If the call is waiting for event, run it */
        if (!conn->wdata.active) {
                /* If in timeout list, remove it */
                if (conn->wdata.inlist) {
                        conn->wdata.inlist = 0;
                        list_remove(&conn->wdata.link);
                }
                conn->wdata.active = 1;
                fibril_add_ready(conn->wdata.fid);
        }

        futex_up(&async_futex);

        return 1;
}

/** Return new incoming message for the current (fibril-local) connection.
 *
 * @param call          Storage where the incoming call data will be stored.
 * @param usecs         Timeout in microseconds. Zero denotes no timeout.
 *
 * @return              If no timeout was specified, then a hash of the
 *                      incoming call is returned. If a timeout is specified,
 *                      then a hash of the incoming call is returned unless
 *                      the timeout expires prior to receiving a message. In
 *                      that case zero is returned.
 */
ipc_callid_t async_get_call_timeout(ipc_call_t *call, suseconds_t usecs)
{
        msg_t *msg;
        ipc_callid_t callid;
        connection_t *conn;
        
        assert(FIBRIL_connection);
        /* GCC 4.1.0 coughs on FIBRIL_connection-> dereference,
         * GCC 4.1.1 happilly puts the rdhwr instruction in delay slot.
         *           I would never expect to find so many errors in 
         *           compiler *($&$(*&$
         */
        conn = FIBRIL_connection; 

        futex_down(&async_futex);

        if (usecs) {
                gettimeofday(&conn->wdata.expires, NULL);
                tv_add(&conn->wdata.expires, usecs);
        } else {
                conn->wdata.inlist = 0;
        }
        /* If nothing in queue, wait until something arrives */
        while (list_empty(&conn->msg_queue)) {
                if (usecs)
                        insert_timeout(&conn->wdata);

                conn->wdata.active = 0;
                fibril_schedule_next_adv(FIBRIL_TO_MANAGER);
                /*
                 * Futex is up after getting back from async_manager get it
                 * again.
                */
                futex_down(&async_futex);
                if (usecs && conn->wdata.timedout &&
                    list_empty(&conn->msg_queue)) {
                        /* If we timed out -> exit */
                        futex_up(&async_futex);
                        return 0;
                }
        }
        
        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;
}

/** Fibril function that gets created on new connection
 *
 * This function is defined as a weak symbol - to be redefined in user code.
 */
static void default_client_connection(ipc_callid_t callid, ipc_call_t *call)
{
        ipc_answer_fast(callid, ENOENT, 0, 0);
}
static void default_interrupt_received(ipc_callid_t callid, ipc_call_t *call)
{
}

/** Wrapper for client connection fibril.
 *
 * When new connection arrives, a fibril with this implementing function is
 * created. It calls client_connection() and does the final cleanup.
 *
 * @param arg           Connection structure pointer
 *
 * @return              Always zero.
 */
static int connection_fibril(void  *arg)
{
        unsigned long key;
        msg_t *msg;
        int close_answered = 0;

        /* Setup fibril-local connection pointer */
        FIBRIL_connection = (connection_t *) arg;
        FIBRIL_connection->cfibril(FIBRIL_connection->callid,
            &FIBRIL_connection->call);
        
        /* Remove myself from connection hash table */
        futex_down(&async_futex);
        key = FIBRIL_connection->in_phone_hash;
        hash_table_remove(&conn_hash_table, &key, 1);
        futex_up(&async_futex);
        
        /* Answer all remaining messages with ehangup */
        while (!list_empty(&FIBRIL_connection->msg_queue)) {
                msg = list_get_instance(FIBRIL_connection->msg_queue.next,
                    msg_t, link);
                list_remove(&msg->link);
                if (msg->callid == FIBRIL_connection->close_callid)
                        close_answered = 1;
                ipc_answer_fast(msg->callid, EHANGUP, 0, 0);
                free(msg);
        }
        if (FIBRIL_connection->close_callid)
                ipc_answer_fast(FIBRIL_connection->close_callid, 0, 0, 0);
        
        return 0;
}

/** Create a new fibril for a new connection.
 *
 * Creates new fibril 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 fibrils.
 *
 * @param in_phone_hash Identification of the incoming connection
 * @param callid        Callid of the IPC_M_CONNECT_ME_TO packet
 * @param call          Call data of the opening packet
 * @param cfibril       Fibril function that should be called upon
 *                      opening the connection
 * @return              New fibril id.
 */
fid_t async_new_connection(ipcarg_t in_phone_hash, ipc_callid_t callid,
    ipc_call_t *call, void (*cfibril)(ipc_callid_t, ipc_call_t *))
{
        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 = in_phone_hash;
        list_initialize(&conn->msg_queue);
        conn->callid = callid;
        conn->close_callid = 0;
        if (call)
                conn->call = *call;
        conn->wdata.active = 1; /* We will activate it asap */
        conn->cfibril = cfibril;

        conn->wdata.fid = fibril_create(connection_fibril, conn);
        if (!conn->wdata.fid) {
                free(conn);
                ipc_answer_fast(callid, ENOMEM, 0, 0);
                return NULL;
        }
        /* Add connection to hash table */
        key = conn->in_phone_hash;
        futex_down(&async_futex);
        hash_table_insert(&conn_hash_table, &key, &conn->link);
        futex_up(&async_futex);

        fibril_add_ready(conn->wdata.fid);

        return conn->wdata.fid;
}

/** Handle a call that was received. */
static void handle_call(ipc_callid_t callid, ipc_call_t *call)
{
        /* Unrouted call - do some default behaviour */
        if ((callid & IPC_CALLID_NOTIFICATION)) {
                in_interrupt_handler = 1;
                (*interrupt_received)(callid,call);
                in_interrupt_handler = 0;
                return;
        }               

        switch (IPC_GET_METHOD(*call)) {
        case IPC_M_CONNECT_ME_TO:
                /* Open new connection with fibril etc. */
                async_new_connection(IPC_GET_ARG3(*call), callid, call,
                    client_connection);
                return;
        }

        /* Try to route call through connection tables */
        if (route_call(callid, call))
                return;

        /* Unknown call from unknown phone - hang it up */
        ipc_answer_fast(callid, EHANGUP, 0, 0);
}

/** Fire all timeouts that expired. */
static void handle_expired_timeouts(void)
{
        struct timeval tv;
        awaiter_t *waiter;
        link_t *cur;

        gettimeofday(&tv,NULL);
        futex_down(&async_futex);

        cur = timeout_list.next;
        while (cur != &timeout_list) {
                waiter = list_get_instance(cur, awaiter_t, link);
                if (tv_gt(&waiter->expires, &tv))
                        break;
                cur = cur->next;
                list_remove(&waiter->link);
                waiter->inlist = 0;
                waiter->timedout = 1;
                /* Redundant condition? The fibril should not
                 * be active when it gets here.
                 */
                if (!waiter->active) {
                        waiter->active = 1;
                        fibril_add_ready(waiter->fid);
                }
        }

        futex_up(&async_futex);
}

/** Endless loop dispatching incoming calls and answers */
static int async_manager_worker(void)
{
        ipc_call_t call;
        ipc_callid_t callid;
        int timeout;
        awaiter_t *waiter;
        struct timeval tv;

        while (1) {
                if (fibril_schedule_next_adv(FIBRIL_FROM_MANAGER)) {
                        futex_up(&async_futex); 
                        /* async_futex is always held
                         * when entering manager fibril
                         */
                        continue;
                }
                futex_down(&async_futex);
                if (!list_empty(&timeout_list)) {
                        waiter = list_get_instance(timeout_list.next, awaiter_t,
                            link);
                        gettimeofday(&tv, NULL);
                        if (tv_gteq(&tv, &waiter->expires)) {
                                futex_up(&async_futex);
                                handle_expired_timeouts();
                                continue;
                        } else
                                timeout = tv_sub(&waiter->expires, &tv);
                } else
                        timeout = SYNCH_NO_TIMEOUT;
                futex_up(&async_futex);

                callid = ipc_wait_cycle(&call, timeout, SYNCH_FLAGS_NONE);

                if (!callid) {
                        handle_expired_timeouts();
                        continue;
                }

                if (callid & IPC_CALLID_ANSWERED) {
                        continue;
                }

                handle_call(callid, &call);
        }
        
        return 0;
}

/** Function to start async_manager as a standalone fibril. 
 * 
 * When more kernel threads are used, one async manager should
 * exist per thread.
 */
static int async_manager_fibril(void *arg)
{
        futex_up(&async_futex);
        /* async_futex is always locked when entering
         * manager */
        async_manager_worker();
        
        return 0;
}

/** Add one manager to manager list */
void async_create_manager(void)
{
        fid_t fid;

        fid = fibril_create(async_manager_fibril, NULL);
        fibril_add_manager(fid);
}

/** Remove one manager from manager list */
void async_destroy_manager(void)
{
        fibril_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;
        }
        
        return 0;
}

/** IPC handler for messages in async framework
 *
 * Notify the fibril which 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; 

        write_barrier();
        /* Remove message from timeout list */
        if (msg->wdata.inlist)
                list_remove(&msg->wdata.link);
        msg->done = 1;
        if (! msg->wdata.active) {
                msg->wdata.active = 1;
                fibril_add_ready(msg->wdata.fid);
        }
        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;

        if (in_interrupt_handler) {
                printf("Cannot send asynchronous request in interrupt "
                    "handler.\n");
                _exit(1);
        }

        msg = malloc(sizeof(*msg));
        msg->done = 0;
        msg->dataptr = dataptr;

        msg->wdata.active = 1; /* We may sleep in next method, but it
                                * will use it's own mechanism */
        ipc_call_async_2(phoneid, method, arg1, arg2, msg, reply_received, 1);

        return (aid_t) msg;
}

/** 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_3(int phoneid, ipcarg_t method, ipcarg_t arg1, ipcarg_t arg2,
    ipcarg_t arg3, ipc_call_t *dataptr)
{
        amsg_t *msg;

        if (in_interrupt_handler) {
                printf("Cannot send asynchronous request in interrupt handler.\n");
                _exit(1);
        }

        msg = malloc(sizeof(*msg));
        msg->done = 0;
        msg->dataptr = dataptr;

        msg->wdata.active = 1; /* We may sleep in next method, but it
                                * will use it's own mechanism */
        ipc_call_async_3(phoneid, method, arg1, arg2, arg3, msg, reply_received,
            1);

        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;

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

        msg->wdata.fid = fibril_get_id();
        msg->wdata.active = 0;
        msg->wdata.inlist = 0;
        /* Leave locked async_futex when entering this function */
        fibril_schedule_next_adv(FIBRIL_TO_MANAGER);
        /* futex is up automatically after fibril_schedule_next...*/
done:
        if (retval)
                *retval = msg->retval;
        free(msg);
}

/** Wait for a message sent by async framework with timeout
 *
 * @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.
 * @param timeout Timeout in usecs
 * @return 0 on success, ETIMEOUT if timeout expired
 *
 */
int async_wait_timeout(aid_t amsgid, ipcarg_t *retval, suseconds_t timeout)
{
        amsg_t *msg = (amsg_t *) amsgid;

        /* TODO: Let it go through the event read at least once */
        if (timeout < 0)
                return ETIMEOUT;

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

        gettimeofday(&msg->wdata.expires, NULL);
        tv_add(&msg->wdata.expires, timeout);

        msg->wdata.fid = fibril_get_id();
        msg->wdata.active = 0;
        insert_timeout(&msg->wdata);

        /* Leave locked async_futex when entering this function */
        fibril_schedule_next_adv(FIBRIL_TO_MANAGER);
        /* futex is up automatically after fibril_schedule_next...*/

        if (!msg->done)
                return ETIMEOUT;

done:
        if (retval)
                *retval = msg->retval;
        free(msg);

        return 0;
}

/** Wait specified time, but in the meantime handle incoming events
 *
 * @param timeout Time in microseconds to wait
 */
void async_usleep(suseconds_t timeout)
{
        amsg_t *msg;
        
        if (in_interrupt_handler) {
                printf("Cannot call async_usleep in interrupt handler.\n");
                _exit(1);
        }

        msg = malloc(sizeof(*msg));
        if (!msg)
                return;

        msg->wdata.fid = fibril_get_id();
        msg->wdata.active = 0;

        gettimeofday(&msg->wdata.expires, NULL);
        tv_add(&msg->wdata.expires, timeout);

        futex_down(&async_futex);
        insert_timeout(&msg->wdata);
        /* Leave locked the async_futex when entering this function */
        fibril_schedule_next_adv(FIBRIL_TO_MANAGER);
        /* futex is up automatically after fibril_schedule_next_adv()...*/
        free(msg);
}

/** Set function that is called when IPC_M_CONNECT_ME_TO is received.
 *
 * @param conn Function that will form a new fibril.
 */
void async_set_client_connection(async_client_conn_t conn)
{
        client_connection = conn;
}
void async_set_interrupt_received(async_client_conn_t conn)
{
        interrupt_received = conn;
}

/* Primitive functions for simple communication */
void async_msg_3(int phoneid, ipcarg_t method, ipcarg_t arg1,
                 ipcarg_t arg2, ipcarg_t arg3)
{
        ipc_call_async_3(phoneid, method, arg1, arg2, arg3, NULL, NULL,
            !in_interrupt_handler);
}

void async_msg_2(int phoneid, ipcarg_t method, ipcarg_t arg1, ipcarg_t arg2)
{
        ipc_call_async_2(phoneid, method, arg1, arg2, NULL, NULL,
            !in_interrupt_handler);
}

/** @}
 */