base/ipc/msg/msg.c

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/** 
 * @file
 * Message handling functions.
 * @author Paolo Mantegazza
 *
 * @note Copyright (C) 1999-2003 Paolo Mantegazza
 * <mantegazza@aero.polimi.it> [ Specific COPYRIGHTS follow along the
 *  code ] 
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * @ingroup msg
 * @ingroup rpc
 */

/**
 * @ingroup sched
 * @defgroup msg Message handling functions
 */

/**
 * @ingroup sched
 * @defgroup rpc Remote procedure call functions
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/version.h>

#include <rtai_schedcore.h>
#include <rtai_prinher.h>

MODULE_LICENSE("GPL");

/* +++++++++++++++++++++++ SHORT INTERTASK MESSAGES +++++++++++++++++++++++++ */

#define TASK_INVAL  ((RT_TASK *)RTE_OBJINV)

#define msg_not_sent() \
do { \
    void *retp; \
    if ((retp = rt_current->blocked_on) != RTP_OBJREM) { \
        set_task_prio_from_resq(task); \
        dequeue_blocked(rt_current); \
        task = (void *)(long)(CONFIG_RTAI_USE_NEWERR ? ((likely(retp > RTP_HIGERR) ? RTE_TIMOUT : RTE_UNBLKD)) : 0); \
    } else { \
        rt_current->prio_passed_to = NULL; \
        task = (void *)(long)(CONFIG_RTAI_USE_NEWERR ? RTE_OBJREM : 0); \
    } \
    rt_current->msg_queue.task = rt_current; \
} while (0)

#define msg_not_received() \
do { \
    rt_current->ret_queue.task = NULL; \
    task = (void *)(long)(CONFIG_RTAI_USE_NEWERR ? (((void *)rt_current->blocked_on != RTP_UNBLKD) ? RTE_TIMOUT : RTE_UNBLKD) : 0); \
} while (0)

/* ++++++++++++++++++++++++++ TASK POINTERS CHECKS +++++++++++++++++++++++++ */

#define CHECK_SENDER_MAGIC(task) \
do { if (task->magic != RT_TASK_MAGIC) return TASK_INVAL; } while (0)

#define CHECK_RECEIVER_MAGIC(task) \
do { if (task && task->magic != RT_TASK_MAGIC) return TASK_INVAL; } while (0)

/* +++++++++++++++++++++++++++++ ASYNC SENDS ++++++++++++++++++++++++++++++++ */

/**
 * @ingroup msg
 * @anchor rt_send
 * @brief Send a message.
 *
 * rt_send sends the message @e msg to the task @e task. If the
 * receiver task is ready to get the message rt_send does not block
 * the sending task, but its execution can be preempted if the
 * receiving task has a higher priority. Otherwise the caller task is
 * blocked and queued up in priority order on the receive list of the sent
 * task.
 *
 * @param task is a pointer to a task structure.
 *
 * @param msg corresponds to the message that has to be sent.
 *
 * @return On success, the pointer to the task that received the message is
 * returned.<br>
 * 0 is returned if the caller is unblocked but the message has not
 * been sent, e.g. the task @e task was killed before receiving the
 * message.<br>
 * A special value is returned as described below in case of
 * a failure:
 * - @b 0xFFFF: @e task does not refer to a valid task.
 * 
 * @note Since all the messaging functions return a task address
 * 0xFFFF could seem an inappropriate return value. However on all the
 * CPUs RTAI runs on 0xFFFF is not an address that can be used by any
 * RTAI task, so it is should be safe always.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_send(RT_TASK *task, unsigned long msg)
{
    DECLARE_RT_CURRENT;
    unsigned long flags;

    CHECK_SENDER_MAGIC(task);

    flags = rt_global_save_flags_and_cli();
    ASSIGN_RT_CURRENT;
    if ((task->state & RT_SCHED_RECEIVE) &&
          (!task->msg_queue.task || task->msg_queue.task == rt_current)) {
        task->msg = msg;
        task->msg_queue.task = rt_current;
        task->ret_queue.task = NULL;
        rem_timed_task(task);
        if (task->state != RT_SCHED_READY && (task->state &= ~(RT_SCHED_RECEIVE | RT_SCHED_DELAYED)) == RT_SCHED_READY) {
            enq_ready_task(task);
            RT_SCHEDULE(task, cpuid);
        }
    } else {
        rt_current->msg = msg;
        rt_current->msg_queue.task = task;
        enqueue_blocked(rt_current, &task->msg_queue, 0);
        rt_current->state |= RT_SCHED_SEND;
        enqueue_resqtsk(task);
        pass_prio(task, rt_current);
        rem_ready_current(rt_current);
        rt_schedule();
    }
    if (rt_current->msg_queue.task != rt_current) {
        msg_not_sent();
    }
    rt_global_restore_flags(flags);
    return task;
}


/**
 * @ingroup msg
 * @anchor rt_send_if
 * @brief Send a message, only if the calling task will not be blocked.
 *
 * rt_send_if sends the message @e msg to the task @e task if the
 * latter is ready to receive, so that the caller task is never
 * blocked, but its execution can be preempted if the receiving task is
 * ready to receive and has a higher priority.
 *
 * @param task is a pointer to a task structure.
 *
 * @param msg corresponds to the message that has to be sent.
 *
 * @return the pointer to the task @e task that received the message 
 * is returned upon success.<br>
 * @e 0 is returned if the message has not been sent.<br>
 * A special value @e 0xFFFF is returned upon failure.<br><br>
 * The errors are described below: 
 * - @b 0: the task @e task was not ready to receive the message.
 * - @b 0xFFFF: @e task does not refer to a valid task.
 *
 * @note Since all the messaging functions return a task address,
 * 0xFFFF could seem an inappropriate return value. However on all the
 * CPUs RTAI runs on 0xFFFF is not an address that can be used by any
 * RTAI task, so it is should be safe always. (FIXME)
 */
RTAI_SYSCALL_MODE RT_TASK *rt_send_if(RT_TASK *task, unsigned long msg)
{
    DECLARE_RT_CURRENT;
    unsigned long flags;

    CHECK_SENDER_MAGIC(task);

    flags = rt_global_save_flags_and_cli();
    ASSIGN_RT_CURRENT;
    if ((task->state & RT_SCHED_RECEIVE) &&
          (!task->msg_queue.task || task->msg_queue.task == rt_current)) {
        task->msg = msg;
        task->msg_queue.task = rt_current;
        task->ret_queue.task = NULL;
        rem_timed_task(task);
        if (task->state != RT_SCHED_READY && (task->state &= ~(RT_SCHED_RECEIVE | RT_SCHED_DELAYED)) == RT_SCHED_READY) {
            enq_ready_task(task);
            RT_SCHEDULE(task, cpuid);
        }
        if (rt_current->msg_queue.task != rt_current) {
            rt_current->msg_queue.task = rt_current;
            task = NULL;
        }
    } else {
        task = NULL;
    }
    rt_global_restore_flags(flags);
    return task;
}


/**
 * @ingroup msg
 * @anchor rt_send_until
 * brief Send a message with an absolute timeout.
 *
 * rt_send_until sends the message @e msg to the task @e task. If the
 * receiver task is ready to get the message, this function does not
 * block the sending task, but its execution can be preempted if the
 * receiving task has a higher priority. Otherwise the caller task is
 * blocked and queued up in priority order on the receive list of the sent
 * task.
 * In this case the function returns if:
 * - the caller task is in the first place of the waiting queue and
 *   the receiver gets the message and has a lower priority;
 * - a timeout occurs;
 * - an error occurs (e.g. the receiver task is killed).
 *
 * @param task is a pointer to a task structure.
 *
 * @param msg corresponds to the message that has to be sent.
 *
 * @param time is the absolute timeout value.
 *
 * @return the pointer to the task that received the message is
 * returned on success i.e. the message received before timeout
 * expiration.<br>
 * 0 is returned if the message has not been sent.
 * A special value is returned on other failure. The errors
 * are described below:  
 * - @b 0: operation timed out, message was not delivered; 
 * - @b 0xFFFF: @e task does not refer to a valid task.
 *
 * See also: @ref rt_send_timed().
 *
 * @note Since all the messaging functions return a task address
 * 0xFFFF could seem an inappropriate return value.  However on all
 * the CPUs RTAI runs on 0xFFFF is not an address that can be used by
 * any RTAI task, so it is should be safe always.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_send_until(RT_TASK *task, unsigned long msg, RTIME time)
{
    DECLARE_RT_CURRENT;
    unsigned long flags;

    CHECK_SENDER_MAGIC(task);

    flags = rt_global_save_flags_and_cli();
    ASSIGN_RT_CURRENT;
    if ((task->state & RT_SCHED_RECEIVE) &&
          (!task->msg_queue.task || task->msg_queue.task == rt_current)) {
        task->msg = msg;
        task->msg_queue.task = rt_current;
        task->ret_queue.task = NULL;
        rem_timed_task(task);
        if (task->state != RT_SCHED_READY && (task->state &= ~(RT_SCHED_RECEIVE | RT_SCHED_DELAYED)) == RT_SCHED_READY) {
            enq_ready_task(task);
            RT_SCHEDULE(task, cpuid);
        }
    } else {
        rt_current->msg_queue.task = task;
        if ((rt_current->resume_time = time) > rt_time_h) {
            rt_current->msg = msg;
            enqueue_blocked(rt_current, &task->msg_queue, 0);
            rt_current->state |= (RT_SCHED_SEND | RT_SCHED_DELAYED);
            enqueue_resqtsk(task);
            pass_prio(task, rt_current);
            rem_ready_current(rt_current);
            enq_timed_task(rt_current);
            rt_schedule();
        } else {
            rt_current->queue.prev = rt_current->queue.next = &rt_current->queue;
        }
    }
    if (rt_current->msg_queue.task != rt_current) {
        msg_not_sent();
    }
    rt_global_restore_flags(flags);
    return task;
}


/**
 * @ingroup msg
 * @anchor rt_send_timed
 * brief Send a message with a relative timeout.
 *
 * rt_send_timed sends the message @e msg to the task @e task. If the 
 * receiver task is ready to get the message, this function does not
 * block the sending task, but its execution can be preempted if the
 * receiving task has a higher priority. Otherwise the caller task is
 * blocked and queued up in priority order on the receive list of the sent
 * task.
 * In this case the function returns if:
 * - the caller task is in the first place of the waiting queue and
 *   the receiver gets the message and has a lower priority;
 * - a timeout occurs;
 * - an error occurs (e.g. the receiver task is killed).
 *
 * @param task is a pointer to a task structure.
 *
 * @param msg corresponds to the message that has to be sent.
 *
 * @param delay is the timeout relative to the current time.
 *
 * @return on success, the pointer to the task that received the
 * message i.e. the message received before timeout expiration.<br>
 * 0 if the message has not been sent.<br>
 * A special value on other failure. The errors
 * are described below:  
 * - @b 0: operation timed out, message was not delivered; 
 * - @b 0xFFFF: @e task does not refer to a valid task.
 *
 * See also: @ref rt_send_until().
 *
 * @note Since all the messaging functions return a task address
 * 0xFFFF could seem an inappropriate return value.  However on all
 * the CPUs RTAI runs on 0xFFFF is not an address that can be used by
 * any RTAI task, so it is should be safe always. (FIXME)
 */

RTAI_SYSCALL_MODE RT_TASK *rt_send_timed(RT_TASK *task, unsigned long msg, RTIME delay)
{
    return rt_send_until(task, msg, get_time() + delay);
}

/* ++++++++++++++++++++++++++++++++ RPCS +++++++++++++++++++++++++++++++++++ */

/**
 * @ingroup rpc
 * @anchor rt_rpc
 * @brief Make a remote procedure call
 *
 * rt_rpc makes a Remote Procedure Call (RPC). rt_rpc is used for
 * synchronous inter task messaging as it sends the message @e msg to the
 * task @e task and blocks waiting until a return is
 * received from the called task. So the caller task is always blocked
 * and queued up in priority order while the receiver
 * inheredits the blocked sender priority if it is higher (lower in value)
 * than its.
 * The receiver task may get the message with any
 * rt_receive function. It can send an answer with @ref rt_return().
 *
 * @param task pointer to a RT_TASK structure.
 *
 * @param msg message to send.
 *
 * @param reply points to a buffer provided by the caller were the
 * returned result message, any 4 bytes integer, is to be place.
 *
 * @return On success, task (the pointer to the task that received the
 * message) is returned. If the message has not been sent (e.g. the
 * task @e task was killed before receiving the message) 0 is returned.
 * On other failure, a special value is returned as described below:
 * - @b 0: the receiver task was killed before receiving the message.
 * - @b 0xFFFF: @e task does not refer to a valid task.
 *
 * See also: rt_receive_*, @ref rt_return(), @ref rt_isrpc().
 *
 * @note Since all the messaging functions return a task address,
 *       0xFFFF could seem an inappropriate return value. However on
 *       all the CPUs RTAI runs on, 0xFFFF is not an address that can
 *       be used by any RTAI task, so it is should be always safe.<br>
 *   The trio @ref rt_rpc(), @ref rt_receive(), @ref rt_return()
 *   implement functions similar to its peers send-receive-replay
 *   found in QNX, except that in RTAI only four bytes messages
 *   contained in any integer can be exchanged. That's so because
 *   it is more efficient and often enough. If you need to pass 
 *       arbitrarely long messages see the extended intertask messaging
 *       functions.  Moreover note also that we prefer
 *   the idea of calling a function by using a message and then
 *   wait for a return value since it is believed to give a better
 *       idea of what is meant for synchronous message passing. For
 *   a more truly QNX like way of inter task messaging use the support
 *   of the upper cased functions: rt_Send-rt_Recieve-rt_Reply.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_rpc(RT_TASK *task, unsigned long to_do, void *result)
{

    DECLARE_RT_CURRENT;
    unsigned long flags;

    CHECK_SENDER_MAGIC(task);

    flags = rt_global_save_flags_and_cli();
    ASSIGN_RT_CURRENT;
    if ((task->state & RT_SCHED_RECEIVE) &&
        (!task->msg_queue.task || task->msg_queue.task == rt_current)) {
        rt_current->msg = task->msg = to_do;
        task->msg_queue.task = rt_current;
        task->ret_queue.task = NULL;
        rem_timed_task(task);
        if (task->state != RT_SCHED_READY && (task->state &= ~(RT_SCHED_RECEIVE | RT_SCHED_DELAYED)) == RT_SCHED_READY) {
            enq_ready_task(task);
        }
        enqueue_blocked(rt_current, &task->ret_queue, 0);
        rt_current->state |= RT_SCHED_RETURN;
    } else {
        rt_current->msg = to_do;
                enqueue_blocked(rt_current, &task->msg_queue, 0);
        rt_current->state |= RT_SCHED_RPC;
    }
    enqueue_resqtsk(task);
    pass_prio(task, rt_current);
    rem_ready_current(rt_current);
    rt_current->msg_queue.task = task;
    RT_SCHEDULE_BOTH(task, cpuid);
    if (rt_current->msg_queue.task == rt_current) {
        *(unsigned long *)result = rt_current->msg;
    } else {
        msg_not_sent();
    }
    rt_global_restore_flags(flags);
    return task;
}


/**
 * @ingroup rpc
 * @anchor rt_rpc_if
 * @brief Make a remote procedure call, only if the calling task will
 * not be blocked.
 *
 * rt_rpc_if tries to make a Remote Procedure Call (RPC). If the
 * receiver task is ready to accept a message rt_rpc_if sends the
 * message @e msg then it always block until a return is received. In
 * this case the caller task is blocked and queued up
 * in priority order while the receiver
 * inheredits the blocked sender priority if it is higher (lower in value)
 * than its.
 * If the receiver is not ready
 * rt_rpc_if returns immediately. The receiver task may get the
 * message with any rt_receive function. It can send the answer with
 * @ref rt_return().
 *
 * @param task pointer to a RT_TASK structure.
 *
 * @param msg message to send.
 *
 * @param reply points to a buffer provided by the caller.
 *
 * @return On success, task (the pointer to the task that received the
 * message) is returned. If message has not been sent, 0 is
 * returned. On other failure, a special value is returned as
 * described below:
 * - @b 0: The task @e task was not ready to receive the message or
 *         it was killed before sending the reply.
 * - @b 0xFFFF: @e task does not refer to a valid task.
 *
 * See also: notes under @ref rt_rpc().
 *
 * @note Since all the messaging functions return a task address,
 *   0xFFFF could seem an inappropriate return value. However on
 *   all the CPUs RTAI runs on, 0xFFFF is not an address that can
 *       be used by any RTAI task, so it is should be safe always.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_rpc_if(RT_TASK *task, unsigned long to_do, void *result)
{
    DECLARE_RT_CURRENT;
    unsigned long flags;

    CHECK_SENDER_MAGIC(task);

    flags = rt_global_save_flags_and_cli();
    ASSIGN_RT_CURRENT;
    if ((task->state & RT_SCHED_RECEIVE) &&
        (!task->msg_queue.task || task->msg_queue.task == rt_current)) {
        rt_current->msg = task->msg = to_do;
        task->msg_queue.task = rt_current;
        task->ret_queue.task = NULL;
        rem_timed_task(task);
        if (task->state != RT_SCHED_READY && (task->state &= ~(RT_SCHED_RECEIVE | RT_SCHED_DELAYED)) == RT_SCHED_READY) {
            enq_ready_task(task);
        }
        enqueue_blocked(rt_current, &task->ret_queue, 0);
        rt_current->state |= RT_SCHED_RETURN;
        enqueue_resqtsk(task);
        pass_prio(task, rt_current);
        rem_ready_current(rt_current);
        rt_current->msg_queue.task = task;
        RT_SCHEDULE_BOTH(task, cpuid);
        if (rt_current->msg_queue.task == rt_current) {
            *(unsigned long *)result = rt_current->msg;
        } else {
            msg_not_sent();
        }
    } else {
        task = NULL;
    }
    rt_global_restore_flags(flags);
    return task;
}


/** 
 * @ingroup rpc
 * @anchor rt_rpc_until
 * @brief Make a remote procedure call with an absolute timeout.
 *
 * rt_rpc_until makes a Remote Procedure Call. It sends the message @e
 * msg to the task @e task then always waits until a return is
 * received or a timeout occurs. So the caller task is always blocked
 * and queued up in priority order while the receiver
 * inheredits the blocked sender priority if it is higher (lower in value)
 * than its. 
 * The receiver task may get the message with any @ref
 * rt_receive() function. It can send the answer with @ref rt_return().
 *
 * @param task pointer to a RT_TASK structure.
 *
 * @param msg message to send.
 *
 * @param reply points to a buffer provided by the caller.
 *
 * @param time is an absolute timeout value.
 *
 * @return On success, task (the pointer to the task that received the
 * message) is returned. If message has not been sent or no answer
 * arrived, 0 is returned.
 * On other failure, a special value is returned as described below:
 * - @b 0: The message could not be sent or the answer did not arrived
 *         in time.  
 * - @b 0xFFFF: @e task does not refer to a valid task.
 *
 * See also: @ref rt_receive(), @ref rt_return(), @ref rt_isrpc().
 *
 * @note Since all the messaging functions return a task address, 0xFFFF
 * could seem an inappropriate return value. However on all the CPUs
 * RTAI runs on, 0xFFFF is not an address that can be used by any RTAI
 * task, so it is should be always safe.<br>
 * See also the notes under @ref rt_rpc().
 */
RTAI_SYSCALL_MODE RT_TASK *rt_rpc_until(RT_TASK *task, unsigned long to_do, void *result, RTIME time)
{
    DECLARE_RT_CURRENT;
    unsigned long flags;

    CHECK_SENDER_MAGIC(task);

    flags = rt_global_save_flags_and_cli();
    ASSIGN_RT_CURRENT;
    if ((rt_current->resume_time = time) <= rt_time_h) {
        rt_global_restore_flags(flags);
        return (RT_TASK *)0;
    }
    if ((task->state & RT_SCHED_RECEIVE) &&
        (!task->msg_queue.task || task->msg_queue.task == rt_current)) {
        rt_current->msg = task->msg = to_do;
        task->msg_queue.task = rt_current;
        task->ret_queue.task = NULL;
        rem_timed_task(task);
        if (task->state != RT_SCHED_READY && (task->state &= ~(RT_SCHED_RECEIVE | RT_SCHED_DELAYED)) == RT_SCHED_READY) {
            enq_ready_task(task);
        }
        enqueue_blocked(rt_current, &task->ret_queue, 0);
        rt_current->state |= (RT_SCHED_RETURN | RT_SCHED_DELAYED);
    } else {
        rt_current->msg = to_do;
        enqueue_blocked(rt_current, &task->msg_queue, 0);
        rt_current->state |= (RT_SCHED_RPC | RT_SCHED_DELAYED);
    }
    enqueue_resqtsk(task);
    pass_prio(task, rt_current);
    rem_ready_current(rt_current);
    rt_current->msg_queue.task = task;
    enq_timed_task(rt_current);
    RT_SCHEDULE_BOTH(task, cpuid);
    if (rt_current->msg_queue.task == rt_current) {
        *(unsigned long *)result = rt_current->msg;
    } else {
        msg_not_sent();
    }
    rt_global_restore_flags(flags);
    return task;
}


/** 
 * @ingroup rpc
 * @anchor rt_rpc_timed
 * @brief Make a remote procedure call with a relative timeout.
 *
 * rt_rpc_timed makes a Remote Procedure Call. It sends the message @e
 * msg to the task @e task then always waits until a return is
 * received or a timeout occurs. So the caller task is always blocked
 * and queued up in priority order while the receiver
 * inheredits the blocked sender priority if it is higher (lower in value)
 * than its.
 * The receiver task may get the message with any @ref
 * rt_receive() function. It can send the answer with @ref rt_return().
 *
 * @param task pointer to a RT_TASK structure.
 *
 * @param msg message to send.
 *
 * @param reply points to a buffer provided by the caller.
 *
 * @param delay is a timeout relative to the current time.
 *
 * @return On success, task (the pointer to the task that received the
 * message) is returned. If message has not been sent or no answer
 * arrived, 0 is returned.
 * On other failure, a special value is returned as described below:
 * - @b 0: The message could not be sent or the answer did not arrived
 *         in time.  
 * - @b 0xFFFF: @e task does not refer to a valid task.
 *
 * See also: @ref rt_receive(), @ref rt_return(), @ref rt_isrpc().
 *
 * @note Since all the messaging functions return a task address, 0xFFFF
 * could seem an inappropriate return value. However on all the CPUs
 * RTAI runs on, 0xFFFF is not an address that can be used by any RTAI
 * task, so it is should be always safe.<br>
 * See also the notes under @ref rt_rpc().
 */
RTAI_SYSCALL_MODE RT_TASK *rt_rpc_timed(RT_TASK *task, unsigned long to_do, void *result, RTIME delay)
{
    return rt_rpc_until(task, to_do, result, get_time() + delay);
}

/* ++++++++++++++++++++++++++++++ RPC_RETURN +++++++++++++++++++++++++++++++ */

/**
 * @ingroup rpc
 * @anchor rt_isrpc
 * @brief Check if sender waits for reply or not.
 *
 * After receiving a message, by calling rt_isrpc a task can figure
 * out whether the sender task @e task is waiting for a reply or
 * not. Such an inquiry may be needed when a server task
 * must provide services to both rt_sends (FIXME) and rt_rtcs.
 * No answer is required if the message is sent by an @e rt_send function
 * or the sender called @ref rt_rpc_timed() or @ref rt_rpc_until() but it
 * is already timed out.
 *
 * @param task pointer to a task structure.
 *
 * @return If the task waits for a return reply, a nonzero value is returned.
 *     Otherwise 0 is returned.
 *
 * @note rt_isrpc does not perform any check on pointer task. rt_isrpc
 *  cannot figure out what RPC result the sender is waiting for.<br>
 * @ref rt_return() is intelligent enough to not send an answer to a
 * task which is not waiting for it. Therefore using rt_isrpc might not
 * be necessary. 
 */
RTAI_SYSCALL_MODE int rt_isrpc(RT_TASK *task)
{
    return task->state & RT_SCHED_RETURN;
}


/**
 * @ingroup rpc
 * @anchor rt_return
 * @brief Return (sends) the result back to the task that made the 
 *  related remote procedure call.
 *
 * rt_return sends the result @e result to the task @e task. If the task
 * calling rt_rpc is not waiting the answer (i.e. killed or
 * timed out) this return message is silently discarded. The returning task
 * tries to release any previously inheredited priority inherediting the 
 * highest priority of any rpcing task still waiting for
 * a return, but only if does not own a resource semaphore. In the latter 
 * case it will keep the eighest inheredited priority till it has released
 * the resource ownership and no further message is waiting for a return.
 * That means that in the case priority inheritance is coming only
 * from rpced messages the task will return to its base priority when no
 * further message is queued for a return. Such a scheme automatically 
 * sets a dynamic priority ceiling in the case priorities are 
 * inheredited both from intertask messaging and resource semaphores 
 * ownership.
 *
 * @return On success, task (the pointer to the task that is got the
 * reply) is returned. If the reply message has not been sent, 0 is
 * returned. On other failure, a special value is returned as
 * described below:
 * - @b 0: The reply message was not delivered.
 * - @b 0xFFFF: @e task does not refer to a valid task.
 *
 * @note Since all the messaging functions return a task address,
 * 0xFFFF could seem an inappropriate return value. However on all the
 * CPUs RTAI runs on, 0xFFFF is not an address that can be used by any
 * RTAI task, so it is should be always safe.
 *
 * See also: notes under @ref rt_rpc().
 */
RTAI_SYSCALL_MODE RT_TASK *rt_return(RT_TASK *task, unsigned long result)
{
    DECLARE_RT_CURRENT;
    unsigned long flags;

    CHECK_SENDER_MAGIC(task);

    flags = rt_global_save_flags_and_cli();
    ASSIGN_RT_CURRENT;
    if ((task->state & RT_SCHED_RETURN) && task->msg_queue.task == rt_current) {
        int sched;
        dequeue_blocked(task);
        sched = set_current_prio_from_resq(rt_current);
        task->msg = result;
        task->msg_queue.task = task;
        rem_timed_task(task);
        if (task->state != RT_SCHED_READY && (task->state &= ~(RT_SCHED_RETURN | RT_SCHED_DELAYED)) == RT_SCHED_READY) {
            enq_ready_task(task);
            if (sched) {
                RT_SCHEDULE_BOTH(task, cpuid);
            } else {
                RT_SCHEDULE(task, cpuid);
            }
                } else if (sched) {
                        rt_schedule();
                }
    } else {
        task = NULL;
    }
    rt_global_restore_flags(flags);
    return task;
}

/* ++++++++++++++++++++++++++++++ RECEIVES +++++++++++++++++++++++++++++++++ */

/**
 * @ingroup msg
 * @anchor rt_evdrp
 * @brief Eavedrop (spy) the content of a message.
 *
 * rt_evdrp spies the content of a message from the task specified by @e task 
 * while leaving it on the queue. To actually receive the message any of the 
 * rt_receive function must be used specifically. If task
 * is equal to 0, the caller eavdrops the first message of its receive queue,
 * if any. rt_evdrp never blocks.
 *
 * @param task is a pointer to a @e RT_TASK structure.
 * 
 * @param msg points to any 4 bytes word buffer provided by the
 * caller. 
 *
 * @return a pointer to the sender task is returned upon success.<br> 
 * 0 is returned if no message is available.
 * A special value is returned on other failure. The errors 
 * are described below:  
 * - @b 0: the sender task was killed before sending the message;
 * - @b 0xFFFF: @e task does not refer to a valid task.
 * 
 * @note Since all the messaging functions return a task address
 * 0xFFFF could seem an inappropriate return value.  However on all
 * the CPUs RTAI runs on 0xFFFF is not an address that can be used by
 * any RTAI task, so it is should be always safe.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_evdrp(RT_TASK *task, void *msg)
{
    DECLARE_RT_CURRENT;

    CHECK_RECEIVER_MAGIC(task);

    ASSIGN_RT_CURRENT;
    if (!task) task = (rt_current->msg_queue.next)->task;
    if ((task->state & (RT_SCHED_SEND | RT_SCHED_RPC)) && task->msg_queue.task == rt_current) {
        *(unsigned long *)msg = task->msg;
    } else {
        task = NULL;
    }
    return task;
}


/**
 * @ingroup msg
 * @anchor rt_receive
 * @brief Receive a message.
 *
 * rt_receive gets a message from the task specified by task. If task
 * is equal to 0, the caller accepts messages from any task. If there
 * is a pending message, rt_receive does not block but can be
 * preempted if the task that rt_sent the just received message has a
 * higher priority. The task will not block if it receives rpced messages
 * since rpcing tasks always waits for a returned message. Moreover it 
 * inheredits the highest priority of any rpcing task waiting on the receive
 * queue. The receiving task will then recover its priority as explained in 
 * rt_return. Otherwise the caller task is blocked waiting for any 
 * message to be sent/rpced.
 *
 * @param task is a pointer to a @e RT_TASK structure.
 * 
 * @param msg points to any 4 bytes word buffer provided by the
 * caller. 
 *
 * @return a pointer to the sender task is returned upon success.<br> 
 * 0 is returned if the caller is unblocked but no message has
 * been received (e.g. the task @e task was killed before sending the
 * message.)<br>
 * A special value is returned on other failure. The errors 
 * are described below:  
 * - @b 0: the sender task was killed before sending the message;
 * - @b 0xFFFF: @e task does not refer to a valid task.
 * 
 * @note Since all the messaging functions return a task address
 * 0xFFFF could seem an inappropriate return value.  However on all
 * the CPUs RTAI runs on 0xFFFF is not an address that can be used by
 * any RTAI task, so it is should be always safe.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_receive(RT_TASK *task, void *msg)
{
    DECLARE_RT_CURRENT;
    unsigned long flags;

    CHECK_RECEIVER_MAGIC(task);

    flags = rt_global_save_flags_and_cli();
    ASSIGN_RT_CURRENT;
    if (!task) task = (rt_current->msg_queue.next)->task;
    if ((task->state & (RT_SCHED_SEND | RT_SCHED_RPC)) && task->msg_queue.task == rt_current) {
        dequeue_blocked(task);
        rem_timed_task(task);
        *(unsigned long *)msg = task->msg;
        rt_current->msg_queue.task = task;
        if (task->state & RT_SCHED_SEND) {
            int sched;
            task->msg_queue.task = task;
            sched = set_current_prio_from_resq(rt_current);
            if (task->state != RT_SCHED_READY && (task->state &= ~(RT_SCHED_SEND | RT_SCHED_DELAYED)) == RT_SCHED_READY) {
                enq_ready_task(task);
                if (sched) {
                    RT_SCHEDULE_BOTH(task, cpuid);
                } else {
                    RT_SCHEDULE(task, cpuid);
                }
            }
        } else if (task->state & RT_SCHED_RPC) {
                        enqueue_blocked(task, &rt_current->ret_queue, 0);
            task->state = (task->state & ~(RT_SCHED_RPC | RT_SCHED_DELAYED)) | RT_SCHED_RETURN;
        }
    } else {
        rt_current->ret_queue.task = RTP_HIGERR;
        rt_current->state |= RT_SCHED_RECEIVE;
        rem_ready_current(rt_current);
        rt_current->msg_queue.task = task != rt_current ? task : (RT_TASK *)0;
        rt_schedule();
        *(unsigned long *)msg = rt_current->msg;
    }
    if (rt_current->ret_queue.task) {
        msg_not_received();
    } else {
        task = rt_current->msg_queue.task;
    }
    rt_current->msg_queue.task = rt_current;
    rt_global_restore_flags(flags);
    if ((unsigned long)task > RTE_HIGERR && (struct proxy_t *)task->stack_bottom) {
        if (((struct proxy_t *)task->stack_bottom)->receiver == rt_current) {
            rt_return(task, 0);
        }
    }
    return task;
}


/**
 * @ingroup msg
 * @anchor rt_receive_if
 * @brief Receive a message, only if the calling task is not blocked.
 * 
 * rt_receive_if tries to get a message from the task specified by
 * task. If task is equal to 0, the caller accepts messages from any
 * task. The caller task is never blocked but can be preempted if the
 * task that rt_sent the just received message has a
 * higher priority. The task will not block if it receives rpced messages
 * since rpcing tasks always waits for a returned message. Moreover it
 * inheredits the highest priority of any rpcing task waiting on the receive
 * queue. The receiving task will then recover its priority as explained in 
 * rt_return. Otherwise the caller task is blocked waiting for any 
 * message to be sent/rpced.
 *
 * @param task is a pointer to the task structure.
 *
 * @param msg points to a buffer provided by the caller.
 *
 * @return a pointer to the sender task is returned upon success.<br>
 * A special value is returned on other failure. The errors are
 * described below:   
 * - @b 0: there was no message to receive;
 * - @b 0xFFFF: @e task does not refer to a valid task.
 *
 * Since all the messaging functions return a task address 0xFFFF
 * could seem an inappropriate return value. However on all the CPUs
 * RTAI runs on 0xFFFF is not an address that can be used by any RTAI
 * task, so it is should be always safe.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_receive_if(RT_TASK *task, void *msg)
{
    DECLARE_RT_CURRENT;
    unsigned long flags;

    CHECK_RECEIVER_MAGIC(task);

    flags = rt_global_save_flags_and_cli();
    ASSIGN_RT_CURRENT;
    if (!task) task = (rt_current->msg_queue.next)->task;
    if ((task->state & (RT_SCHED_SEND | RT_SCHED_RPC)) && task->msg_queue.task == rt_current) {
        dequeue_blocked(task);
        rem_timed_task(task);
        *(unsigned long *)msg = task->msg;
        rt_current->msg_queue.task = task;
        if (task->state & RT_SCHED_SEND) {
            int sched;
            task->msg_queue.task = task;
            sched = set_current_prio_from_resq(rt_current);
            if (task->state != RT_SCHED_READY && (task->state &= ~(RT_SCHED_SEND | RT_SCHED_DELAYED)) == RT_SCHED_READY) {
                enq_ready_task(task);
                if (sched) {
                    RT_SCHEDULE_BOTH(task, cpuid);
                } else {
                    RT_SCHEDULE(task, cpuid);
                }
            }
        } else if (task->state & RT_SCHED_RPC) {
            enqueue_blocked(task, &rt_current->ret_queue, 0);
            task->state = (task->state & ~(RT_SCHED_RPC | RT_SCHED_DELAYED)) | RT_SCHED_RETURN;
        }
        if (rt_current->ret_queue.task) {
            rt_current->ret_queue.task = NULL;
            task = NULL;
        } else {
            task = rt_current->msg_queue.task;
        }
        rt_current->msg_queue.task = rt_current;
    } else {
        task = NULL;
    }
    rt_global_restore_flags(flags);
    if ((unsigned long)task > RTE_HIGERR && (struct proxy_t *)task->stack_bottom) {
        if (((struct proxy_t *)task->stack_bottom)->receiver == rt_current) {
            rt_return(task, 0);
        }
    }
    return task;
}


/**
 * @ingroup msg
 * @anchor rt_receive_until
 * @brief Receive a message with an absolute timeout.
 *
 * rt_receive_until receives a message from the task specified by
 * task. If task is equal to 0, the caller accepts messages from any
 * task. If there is a pending message, rt_receive does not block but
 * but can be preempted if the
 * task that rt_sent the just received message has a
 * higher priority. The task will not block if it receives rpced messages
 * since rpcing tasks always waits for a returned message. Moreover it
 * inheredits the highest priority of any rpcing task waiting on the receive
 * queue. The receiving task will then recover its priority as explained in 
 * rt_return. Otherwise the caller task is blocked waiting for any
 * message to be sent/rpced.
 * In this case these functions return if:
 *   a sender sends a message and has a lower priority;
 *   any rpced message is received;
 * - timeout occurs;
 * - an error occurs (e.g. the sender task is killed.)
 *
 * @param task is a pointer to the task structure.
 *
 * @param msg points to a buffer provided by the caller.
 *
 * @param time is an absolute timout value.
 *
 * @return On success, a pointer to the sender task is returned.
 * On other failure, a special value is returned. The errors
 * are described below:  
 * - @b 0: there was no message to receive.
 * - @b 0xFFFF: @e task does not refer to a valid task.
 *
 * @note Since all the messaging functions return a task address
 * 0xFFFF could seem an inappropriate return value. However on all
 * the CPUs RTAI runs on 0xFFFF is not an address that can be used by
 * any RTAI task, so it is should be always safe.
 *
 * See also: @ref rt_receive_timed().
 */
RTAI_SYSCALL_MODE RT_TASK *rt_receive_until(RT_TASK *task, void *msg, RTIME time)
{
    DECLARE_RT_CURRENT;
    unsigned long flags;

    CHECK_RECEIVER_MAGIC(task);

    flags = rt_global_save_flags_and_cli();
    ASSIGN_RT_CURRENT;
    if (!task) task = (rt_current->msg_queue.next)->task;
    if ((task->state & (RT_SCHED_SEND | RT_SCHED_RPC)) && task->msg_queue.task == rt_current) {
        dequeue_blocked(task);
        rem_timed_task(task);
        *(unsigned long *)msg = task->msg;
        rt_current->msg_queue.task = task;
        if (task->state & RT_SCHED_SEND) {
            int sched;
            task->msg_queue.task = task;
            sched = set_current_prio_from_resq(rt_current);
            if (task->state != RT_SCHED_READY && (task->state &= ~(RT_SCHED_SEND | RT_SCHED_DELAYED)) == RT_SCHED_READY) {
                enq_ready_task(task);
                if (sched) {
                    RT_SCHEDULE_BOTH(task, cpuid);
                } else {
                    RT_SCHEDULE(task, cpuid);
                }
            }
        } else if (task->state & RT_SCHED_RPC) {
            enqueue_blocked(task, &rt_current->ret_queue, 0);
            task->state = (task->state & ~(RT_SCHED_RPC | RT_SCHED_DELAYED)) | RT_SCHED_RETURN;
        }
    } else {
        rt_current->ret_queue.task = RTP_HIGERR;
        if ((rt_current->resume_time = time) > rt_time_h) {
            rt_current->state |= (RT_SCHED_RECEIVE | RT_SCHED_DELAYED);
            rem_ready_current(rt_current);
            rt_current->msg_queue.task = task != rt_current ? task : (RT_TASK *)0;
            enq_timed_task(rt_current);
            rt_schedule();
            *(unsigned long *)msg = rt_current->msg;
        }
    }
    if (rt_current->ret_queue.task) {
        msg_not_received();
    } else {
        task = rt_current->msg_queue.task;
    }
    rt_current->msg_queue.task = rt_current;
    rt_global_restore_flags(flags);
    if ((unsigned long)task > RTE_HIGERR && (struct proxy_t *)task->stack_bottom) {
        if (((struct proxy_t *)task->stack_bottom)->receiver == rt_current) {
            rt_return(task, 0);
        }
    }
    return task;
}


/**
 * @ingroup msg
 * @anchor rt_receive_timed
 * @brief Receive a message with a relative timeout.
 *
 * rt_receive_timed receives a message from the task specified by
 * task. If task is equal to 0, the caller accepts messages from any
 * task. 
 * If there is a pending message, rt_receive does not block but
 * but can be preempted if the
 * task that rt_sent the just received message has a
 * higher priority. The task will not block if it receives rpced messages
 * since rpcing tasks always waits for a returned message. Moreover it
 * inheredits the highest priority of any rpcing task waiting on the receive
 * queue. The receiving task will then recover its priority as explained in 
 * rt_return. Otherwise the caller task is blocked waiting for any
 * message to be sent/rpced.
 * In this case these functions return if:
 *   a sender sends a message and has a lower priority;
 *   any rpced message is received;
 * - timeout occurs;
 * - an error occurs (e.g. the sender task is killed.)
 *
 * @param task is a pointer to the task structure.
 *
 * @param msg points to a buffer provided by the caller.
 *
 * @param delay is a timeout relative to the current time.
 *
 * @return On success, a pointer to the sender task is returned.
 * On other failure, a special value is returned. The errors
 * are described below:  
 * - @b 0: there was no message to receive.
 * - @b 0xFFFF: @e task does not refer to a valid task.
 *
 * @note Since all the messaging functions return a task address
 * 0xFFFF could seem an inappropriate return value. However on all
 * the CPUs RTAI runs on 0xFFFF is not an address that can be used by
 * any RTAI task, so it is should be always safe.
 *
 * See also: @ref rt_receive_until().
 */
RTAI_SYSCALL_MODE RT_TASK *rt_receive_timed(RT_TASK *task, void *msg, RTIME delay)
{
    return rt_receive_until(task, msg, get_time() + delay);
}

/* ++++++++++++++++++++++++++ EXTENDED MESSAGES +++++++++++++++++++++++++++++++
COPYRIGHT (C) 2003  Pierre Cloutier  (pcloutier@poseidoncontrols.com)
                    Paolo Mantegazza (mantegazza@aero.polimi.it)
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */

#define SET_RPC_MCB() \
    do { \
        mcb.sbuf   = smsg; \
        mcb.sbytes = ssize; \
        mcb.rbuf   = rmsg; \
        mcb.rbytes = rsize; \
    } while (0)

/**
 * @ingroup rpc
 * @anchor rt_rpcx
 * @brief Make an extended remote procedure call
 *
 * rt_rpcx makes an extended Remote Procedure Call (RPC). rt_rpcx is used for
 * synchronous inter task messaging. It sends an arbitrary @e smsg of size
 * @e ssize bytes to the task @e task then it always blocks waiting until a 
 * message, of size @e rsize bytes at most, is returned in @e rmsg from the 
 * called task. If the returned message is greater tha rsize it will be 
 * truncated. So the caller task is always blocked on the receiver priority 
 * queue while the receiver inheredits the blocked sender priority if it is 
 * higher (lower in value) than its. The receiver task may get the message 
 * with any rt_receivex function. It can send an answer with @ref rt_returnx().
 *
 * @param task pointer to the RT_TASK structure of the receiver.
 *
 * @param smsg points to the message to be sent.
 *
 * @param rmsg points to the message to be returned by the receiver.
 *
 * @param ssize size of the message to be sent.
 *
 * @param rsize maximum allowed size for the message to be received.
 *
 * @return On success, task (the pointer to the task that received the
 * message) is returned. If the message has not been sent (e.g. the
 * task @e task was killed before receiving the message) 0 is returned.
 *
 * See also: rt_receivex_*, @ref rt_returnx(), @ref rt_isrpc().
 *
 * @note The trio @ref rt_rpcx(), @ref rt_receivex(), @ref rt_returnx()
 *   implements functions similar to its peers send-receive-reply
 *   found in QNX. For a even greater compatibility see
 *       rt_Send-rt_Receive-rt_Reply.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_rpcx(RT_TASK *task, void *smsg, void *rmsg, int ssize, int rsize)
{
    if (task) {
        struct mcb_t mcb;
        SET_RPC_MCB();
        return rt_rpc(task, (unsigned long)&mcb, &mcb.rbytes);
    }
    return 0;
}


/**
 * @ingroup rpc
 * @anchor rt_rpcx_if
 * @brief Make an extended remote procedure call, only if the calling task 
 * will not be blocked.
 *
 * rt_rpcx_if tries to make an extended Remote Procedure Call (RPC). If the
 * receiver task is ready to accept a message rt_rpcx_if sends the
 * message as it will be done by rt_rpcx.
 * If the receiver is not ready rt_rpcx_if returns immediately. The receiver 
 * task may get the message with any rt_receivex function. It can send the 
 * answer with * @ref rt_returnx().
 *
 * @param task pointer to the RT_TASK structure of the receiver.
 *
 * @param smsg points to the message to be sent.
 *
 * @param rmsg points to the message to be returned by the receiver.
 *
 * @param ssize size of the message to be sent.
 *
 * @param rsize maximum allowed size for the message to be received.
 *
 * @return On success, task (the pointer to the task that received the
 * message) is returned. If message has not been sent, 0 is
 * returned. On other failure, a special value is returned as
 * described below:
 * - @b 0: The task @e task was not ready to receive the message or
 *         it was killed before sending the reply.
 * - @b 0xFFFF: @e task does not refer to a valid task.
 *
 * See also: notes under @ref rt_rpc().
 *
 * @note Since all the messaging functions return a task address,
 *   0xFFFF could seem an inappropriate return value. However on
 *   all the CPUs RTAI runs on, 0xFFFF is not an address that can
 *       be used by any RTAI task, so it is should be always safe.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_rpcx_if(RT_TASK *task, void *smsg, void *rmsg, int ssize, int rsize)
{
    if (task) {
        struct mcb_t mcb;
        SET_RPC_MCB();
        return rt_rpc_if(task, (unsigned long)&mcb, &mcb.rbytes);
    }
    return 0;
}


/** 
 * @ingroup rpc
 * @anchor rt_rpcx_until
 * @brief Make an extended remote procedure call with absolute timeout.
 *
 * rt_rpcx_until makes an extended Remote Procedure Call (RPC). 
 * It sends an arbitrary @e smsg of size @e ssize bytes to the task @e task 
 * then it always blocks waiting until a message, of size @e rsize bytes at 
 * most, is returned in @e rmsg from the called task or a timeout occurs. 
 * If the returned message is greater tha rsize it will be truncated. 
 * So the caller task is always blocked on the receiver priority queue while
 * the receiver inheredits the blocked sender priority if it is higher 
 * (lower in value) than its. The receiver task may get the message with any 
 * rt_receivex function. It can send an answer with @ref rt_returnx().
 *
 * @param task pointer to the RT_TASK structure of the receiver.
 *
 * @param smsg points to the message to be sent.
 *
 * @param rmsg points to the message to be returned by the receiver.
 *
 * @param ssize size of the message to be sent.
 *
 * @param rsize maximum allowed size for the message to be received.
 *
 * @param time is an absolute timeout value.
 *
 * @return On success, task (the pointer to the task that received the
 * message) is returned. If message has not been sent or no answer
 * arrived, 0 is returned.
 * On other failure, a special value is returned as described below:
 * - @b 0: The message could not be sent or the answer did not arrived
 *         in time.  
 * - @b 0xFFFF: @e task does not refer to a valid task.
 *
 * See also: @ref rt_receive(), @ref rt_return(), @ref rt_isrpc().
 *
 * @note Since all the messaging functions return a task address, 0xFFFF
 * could seem an inappropriate return value. However on all the CPUs
 * RTAI runs on, 0xFFFF is not an address that can be used by any RTAI
 * task, so it is should be always safe.<br>
 * See also the notes under @ref rt_rpc().
 */
RTAI_SYSCALL_MODE RT_TASK *rt_rpcx_until(RT_TASK *task, void *smsg, void *rmsg, int ssize, int rsize, RTIME time)
{
    if (task) {
        struct mcb_t mcb;
        SET_RPC_MCB();
        return rt_rpc_until(task, (unsigned long)&mcb, &mcb.rbytes, time);
    }
    return 0;
}


/** 
 * @ingroup rpc
 * @anchor rt_rpcx_timed
 * @brief Make an extended remote procedure call with a relative timeout.
 *
 * rt_rpcx_timed makes an extended Remote Procedure Call (RPC). 
 * It sends an arbitrary @e smsg of size @e ssize bytes to the task @e task 
 * then it always blocks waiting until a message, of size @e rsize bytes at 
 * most, is returned in @e rmsg from the called task or a timeout occurs. 
 * If the returned message is greater tha rsize it will be truncated. 
 * So the caller task is always blocked on the receiver priority queue while
 * the receiver inheredits the blocked sender priority if it is higher 
 * (lower in value) than its. The receiver task may get the message with any 
 * rt_receivex function. It can send an answer with @ref rt_returnx().
 *
 * @param task pointer to the RT_TASK structure of the receiver.
 *
 * @param smsg points to the message to be sent.
 *
 * @param rmsg points to the message to be returned by the receiver.
 *
 * @param ssize size of the message to be sent.
 *
 * @param rsize maximum allowed size for the message to be received.
 *
 * @param delay is the relative timeout.
 *
 * @return On success, task (the pointer to the task that received the
 * message) is returned. If message has not been sent or no answer
 * arrived, 0 is returned.
 * On other failure, a special value is returned as described below:
 * - @b 0: The message could not be sent or the answer did not arrived
 *         in time.  
 * - @b 0xFFFF: @e task does not refer to a valid task.
 *
 * See also: @ref rt_receive(), @ref rt_return(), @ref rt_isrpc().
 *
 * @note Since all the messaging functions return a task address, 0xFFFF
 * could seem an inappropriate return value. However on all the CPUs
 * RTAI runs on, 0xFFFF is not an address that can be used by any RTAI
 * task, so it is should be always safe.<br>
 * See also the notes under @ref rt_rpc().
 */
RTAI_SYSCALL_MODE RT_TASK *rt_rpcx_timed(RT_TASK *task, void *smsg, void *rmsg, int ssize, int rsize, RTIME delay)
{
    if (task) {
        struct mcb_t mcb;
        SET_RPC_MCB();
        return rt_rpc_timed(task, (unsigned long)&mcb, &mcb.rbytes, delay);
    }
    return 0;
}

#define task_mcb (task->mcb)
#define SET_SEND_MCB() \
    do { \
        task_mcb.sbuf   = msg; \
        task_mcb.sbytes = size; \
        task_mcb.rbuf   = 0; \
        task_mcb.rbytes = 0; \
    } while (0)

/**
 * @ingroup msg
 * @anchor rt_sendx
 * @brief Send an extended message.
 *
 * rt_sendx sends an arbitrary message @e msg of size @e size bytes to the task 
 * @e task. If the
 * receiver task is ready to get the message rt_sendx does not block
 * the sending task, but its execution can be preempted if the
 * receiving task has a higher priority. Otherwise the caller task is
 * blocked and queued up in priority order on the receive list of the sent
 * task.
 *
 * @param task is a pointer to a task structure.
 *
 * @param msg points to the message to be sent.
 *
 * @param size size of the message to be sent.
 *
 * @return On success, the pointer to the task that received the message is
 * returned.<br>
 * 0 is returned if the caller is unblocked but the message has not
 * been sent, e.g. the task @e task was killed before receiving the
 * message.<br>
 * A special value is returned as described below in case of
 * a failure:
 * - @b 0xFFFF: @e task does not refer to a valid task.
 * 
 * @note Since all the messaging functions return a task address
 * 0xFFFF could seem an inappropriate return value. However on all the
 * CPUs RTAI runs on 0xFFFF is not an address that can be used by any
 * RTAI task, so it is should be safe always.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_sendx(RT_TASK *task, void *msg, int size) 
{
    if (task) {
        SET_SEND_MCB();
        return rt_send(task, (unsigned long)&task_mcb);
    }
    return 0;
}


/**
 * @ingroup msg
 * @anchor rt_sendx_if
 * @brief Send an extended message, only if the calling task will not be 
 * blocked.
 *
 * rt_sendx_if sends an arbitrary message @e msg of size @e size bytes to the 
 * task @e task if the latter is ready to receive. So the caller task in never
 * blocked but its execution can be preempted if the
 * receiving task has a higher priority.
 *
 * @param task is a pointer to a task structure.
 *
 * @param msg points to the message to be sent.
 *
 * @param size size of the message to be sent.
 *
 * @return On success, the pointer to the task that received the message is
 * returned.<br>
 * 0 is returned if the caller is unblocked but the message has not
 * been sent, e.g. the task @e task was killed before receiving the
 * message.<br>
 * A special value is returned as described below in case of
 * a failure:
 * - @b 0xFFFF: @e task does not refer to a valid task.
 * 
 * @note Since all the messaging functions return a task address
 * 0xFFFF could seem an inappropriate return value. However on all the
 * CPUs RTAI runs on 0xFFFF is not an address that can be used by any
 * RTAI task, so it is should be safe always.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_sendx_if(RT_TASK *task, void *msg, int size)
{
    if (task) {
        SET_SEND_MCB();
        return rt_send_if(task, (unsigned long)&task_mcb);
    }
    return 0;
}


/**
 * @ingroup msg
 * @anchor rt_sendx_until
 * @brief Send an extended message with absolute timeout.
 *
 * rt_sendx_until sends an arbitrary message @e msg of size @e size bytes to 
 * the task @e task. If the
 * receiver task is ready to get the message rt_sendx_until does not block
 * the sending task, but its execution can be preempted if the
 * receiving task has a higher priority. Otherwise the caller task is
 * blocked and queued up in priority order on the receive list of the sent
 * task.
 * In this case the function returns if:
 * - the caller task is in the first place of the waiting queue and
 *   the receiver gets the message and has a lower priority;
 * - a timeout occurs;
 * - an error occurs (e.g. the receiver task is killed).
 *
 * @param task is a pointer to a task structure.
 *
 * @param msg points to the message to be sent.
 *
 * @param size size of the message to be sent.
 *
 * @param time is an absolute timeout value.
 *
 * @return On success, the pointer to the task that received the message is
 * returned.<br>
 * 0 is returned if the caller is unblocked but the message has not
 * been sent, e.g. the task @e task was killed before receiving the
 * message.<br>
 * A special value is returned as described below in case of
 * a failure:
 * - @b 0: operation timed out, message was not delivered;
 * - @b 0xFFFF: @e task does not refer to a valid task.
 * 
 * @note Since all the messaging functions return a task address
 * 0xFFFF could seem an inappropriate return value. However on all the
 * CPUs RTAI runs on 0xFFFF is not an address that can be used by any
 * RTAI task, so it is should be safe always.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_sendx_until(RT_TASK *task, void *msg, int size, RTIME time)
{
    if (task) {
        SET_SEND_MCB();
        return rt_send_until(task, (unsigned long)&task_mcb, time);
    }
    return 0;
}


/**
 * @ingroup msg
 * @anchor rt_sendx_timed
 * @brief Send an extended message with relative timeout.
 *
 * rt_sendx_until sends an arbitrary message @e msg of size @e size bytes to 
 * the task @e task. If the
 * receiver task is ready to get the message rt_sendx_until does not block
 * the sending task, but its execution can be preempted if the
 * receiving task has a higher priority. Otherwise the caller task is
 * blocked and queued up in priority order on the receive list of the sent
 * task.
 * In this case the function returns if:
 * - the caller task is in the first place of the waiting queue and
 *   the receiver gets the message and has a lower priority;
 * - a timeout occurs;
 * - an error occurs (e.g. the receiver task is killed).
 *
 * @param task is a pointer to a task structure.
 *
 * @param msg points to the message to be sent.
 *
 * @param size size of the message to be sent.
 *
 * @param delay is r timeout elative to the current time.
 *
 * @return On success, the pointer to the task that received the message is
 * returned.<br>
 * 0 is returned if the caller is unblocked but the message has not
 * been sent, e.g. the task @e task was killed before receiving the
 * message.<br>
 * A special value is returned as described below in case of
 * a failure:
 * - @b 0: operation timed out, message was not delivered;
 * - @b 0xFFFF: @e task does not refer to a valid task.
 * 
 * @note Since all the messaging functions return a task address
 * 0xFFFF could seem an inappropriate return value. However on all the
 * CPUs RTAI runs on 0xFFFF is not an address that can be used by any
 * RTAI task, so it is should be safe always.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_sendx_timed(RT_TASK *task, void *msg, int size, RTIME delay)
{
    if (task) {
        SET_SEND_MCB();
        return rt_send_timed(task, (unsigned long)&task_mcb, delay);
    }
    return 0;
}


/**
 * @ingroup rpc
 * @anchor rt_returnx
 * @brief Return (sends) an extended result back to the task that made the 
 *  related extended remote procedure call.
 *
 * rt_returns sends the result @e msg of size @e size to the task @e task. 
 * If the task calling rt_rpcx is not waiting the answer (i.e. killed or
 * timed out) this return message is silently discarded. The returning task
 * tries to release any previously inheredited priority inherediting the 
 * highest priority of any rpcing task still waiting for
 * a return, but only if does not own a resource semaphore. In the latter 
 * case it will keep the eighest inheredited priority till it has released
 * the resource ownership and no further message is waiting for a return.
 * That means that in the case priority inheritance is coming only
 * from rpced messages the task will return to its base priority when no
 * further message is queued for a return. Such a scheme automatically 
 * sets a dynamic priority ceiling in the case priorities are 
 * inheredited both from intertask messaging and resource semaphores 
 * ownership.
 *
 * @return On success, task (the pointer to the task that is got the
 * reply) is returned. If the reply message has not been sent, 0 is
 * returned. On other failure, a special value is returned as
 * described below:
 * - @b 0: The reply message was not delivered.
 * - @b 0xFFFF: @e task does not refer to a valid task.
 *
 * @note Since all the messaging functions return a task address,
 * 0xFFFF could seem an inappropriate return value. However on all the
 * CPUs RTAI runs on, 0xFFFF is not an address that can be used by any
 * RTAI task, so it is should be always safe.
 *
 * See also: notes under @ref rt_rpcx().
 */
RTAI_SYSCALL_MODE RT_TASK *rt_returnx(RT_TASK *task, void *msg, int size)
{
    if (task) {
        struct mcb_t *mcb;
        if ((mcb = (struct mcb_t *)task->msg)->rbytes < size) {
            size = mcb->rbytes;
        }
        if (size) {
            memcpy(mcb->rbuf, msg, size);
        }
        return rt_return(task, 0);
    }
    return 0;
}

#define DO_RCV_MSG() \
    do { \
        if ((*len = size <= mcb->sbytes ? size : mcb->sbytes)) { \
            memcpy(msg, mcb->sbuf, *len); \
        } \
    } while (0)


/**
 * @ingroup msg
 * @anchor rt_evdrpx
 * @brief Eavedrop (spy) the content of an extended message.
 *
 * rt_evdrpx spies the content of a message from the task specified by @e task 
 * while leaving it on the queue. To actually receive the message any of the 
 * rt_receivex function must be used specifically. If task
 * is equal to 0, the caller eavdrops the first message of its receive queue,
 * if any. rt_evdrpix never blocks.
 *
 * @param task is a pointer to a @e RT_TASK structure.
 * 
 * @param msg points to the message to be eavedropped, without receive.
 *
 * @param size size of the message to be eavedropped.
 *
 * @param len is a pointer to an integer to be set to the actual len of the
 * eavedropped message.
 *
 * @return a pointer to the sender task is returned upon success.<br> 
 * 0 is returned if no message is available.
 * A special value is returned on other failure. The errors 
 * are described below:  
 * - @b 0: the sender task was killed before sending the message;
 * - @b 0xFFFF: @e task does not refer to a valid task.
 * 
 * @note Since all the messaging functions return a task address
 * 0xFFFF could seem an inappropriate return value.  However on all
 * the CPUs RTAI runs on 0xFFFF is not an address that can be used by
 * any RTAI task, so it is should be always safe.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_evdrpx(RT_TASK *task, void *msg, int size, long *len)
{
    struct mcb_t *mcb;
    if ((task = rt_evdrp(task, (unsigned long *)&mcb))) {
        DO_RCV_MSG();
        return task;
    }
    return 0;
}


/**
 * @ingroup msg
 * @anchor rt_receivex
 * @brief Receive an extended message.
 *
 * rt_receivex gets an extended message @a msg of size @a size from the task 
 * specified by @e task task. If task
 * is equal to 0, the caller accepts messages from any task. If there
 * is a pending message, rt_receivex does not block but can be
 * preempted if the task that rt_sent the just received message has a
 * higher priority. The task will not block if it receives rpcxed messages
 * since rpcxing tasks always wait for a returned message. Moreover it 
 * inheredits the highest priority of any rpcxing task waiting on the receive
 * queue. The receiving task will then recover its priority as explained in 
 * rt_returnx. Otherwise the caller task is blocked waiting for any 
 * message to be sentx/rpcxed.
 *
 * @param task is a pointer to a @e RT_TASK structure.
 * 
 * @param msg points to the message to be eavedropped, without receive.
 *
 * @param size size of the message to be eavedropped.
 *
 * @param len is a pointer to an integer to be set to the actual len of the
 * eavedropped message.
 *
 * @return a pointer to the sender task is returned upon success.<br> 
 * 0 is returned if the caller is unblocked but no message has
 * been received (e.g. the task @e task was killed before sending the
 * message.)<br>
 * A special value is returned on other failure. The errors 
 * are described below:  
 * - @b 0: the sender task was killed before sending the message;
 * - @b 0xFFFF: @e task does not refer to a valid task.
 * 
 * @note Since all the messaging functions return a task address
 * 0xFFFF could seem an inappropriate return value.  However on all
 * the CPUs RTAI runs on 0xFFFF is not an address that can be used by
 * any RTAI task, so it is should be always safe.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_receivex(RT_TASK *task, void *msg, int size, long *len)
{
    struct mcb_t *mcb;
    if ((task = rt_receive(task, (unsigned long *)&mcb))) {
        DO_RCV_MSG();
        return task;
    }
    return 0;
}


/**
 * @ingroup msg
 * @anchor rt_receivex_if
 * @brief Receive an extended message, only if the calling task is not blocked.
 *
 * rt_receivex gets an extended message @a msg of size @a size from the task 
 * specified by @e task task. If task
 * is equal to 0, the caller accepts messages from any task. The caller task 
 * is never blocked but can be preempted if the task that rt_sentx the just 
 * received message has a higher priority.
 * The task will not block if it receives rpcxed messages
 * since rpcxing tasks always wait for a returned message. Moreover it 
 * inheredits the highest priority of any rpcxing task waiting on the receive
 * queue. The receiving task will then recover its priority as explained in 
 * rt_returnx. Otherwise the caller task is blocked waiting for any 
 * message to be sentx/rpcxed.
 *
 * @param task is a pointer to a @e RT_TASK structure.
 * 
 * @param msg points to the message to be eavedropped, without receive.
 *
 * @param size size of the message to be eavedropped.
 *
 * @param len is a pointer to an integer to be set to the actual len of the
 * eavedropped message.
 *
 * @return a pointer to the sender task is returned upon success.<br> 
 * 0 is returned if the caller is unblocked but no message has
 * been received (e.g. the task @e task was killed before sending the
 * message.)<br>
 * A special value is returned on other failure. The errors 
 * are described below:  
 * - @b 0: the sender task was killed before sending the message;
 * - @b 0xFFFF: @e task does not refer to a valid task.
 * 
 * @note Since all the messaging functions return a task address
 * 0xFFFF could seem an inappropriate return value.  However on all
 * the CPUs RTAI runs on 0xFFFF is not an address that can be used by
 * any RTAI task, so it is should be always safe.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_receivex_if(RT_TASK *task, void *msg, int size, long *len)
{
    struct mcb_t *mcb;
    if ((task = rt_receive_if(task, (unsigned long *)&mcb))) {
        DO_RCV_MSG();
        return task;
    }
    return 0;
}


/**
 * @ingroup msg
 * @anchor rt_receivex_until
 * @brief Receive an extended message with an absolute timeout.
 *
 * rt_receivex_until gets an extended message @a msg of size @a size from the
 * task specified by @e task task. If task is equal to 0, the caller accepts
 * messages from any task. If there is a pending message, rt_receivex does not
 * block but can be preempted if the task that rt_sent the just received message
 * has a higher priority. The task will not block if it receives rpcxed messages
 * since rpcxing tasks always wait for a returned message. Moreover it
 * inheredits the highest priority of any rpcxing task waiting on the receive
 * queue. The receiving task will then recover its priority as explained in
 * rt_returnx. Otherwise the caller task is blocked waiting for any message to
 * be sentx/rpcxed.
 *
 * In this case these functions return if:
 *   a sender sendxs a message and has a lower priority;
 *   any rpcxed message is received;
 * - timeout occurs;
 * - an error occurs (e.g. the sender task is killed.)
 * @param task is a pointer to a @e RT_TASK structure.
 * 
 * @param msg points to the message to be eavedropped, without receive.
 *
 * @param size size of the message to be eavedropped.
 *
 * @param len is a pointer to an integer to be set to the actual len of the
 * eavedropped message.
 *
 * @param time is an absolute timout value.
 *
 * @return a pointer to the sender task is returned upon success.<br> 
 * 0 is returned if the caller is unblocked but no message has
 * been received (e.g. the task @e task was killed before sending the
 * message.)<br>
 * A special value is returned on other failure. The errors 
 * are described below:  
 * - @b 0: the sender task was killed before sending the message;
 * - @b 0xFFFF: @e task does not refer to a valid task.
 * 
 * @note Since all the messaging functions return a task address
 * 0xFFFF could seem an inappropriate return value.  However on all
 * the CPUs RTAI runs on 0xFFFF is not an address that can be used by
 * any RTAI task, so it is should be always safe.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_receivex_until(RT_TASK *task, void *msg, int size, long *len, RTIME time)
{
    struct mcb_t *mcb;
    if ((task = rt_receive_until(task, (unsigned long *)&mcb, time))) {
        DO_RCV_MSG();
        return task;
    }
    return 0;
}


/**
 * @ingroup msg
 * @anchor rt_receivex_timed
 * @brief Receive an extended message with a relative timeout.
 *
 * rt_receivex_until gets an extended message @a msg of size @a size from the
 * task specified by @e task task. If task is equal to 0, the caller accepts
 * messages from any task. If there is a pending message, rt_receivex does not
 * block but can be preempted if the task that rt_sent the just received message
 * has a higher priority. The task will not block if it receives rpcxed messages
 * since rpcxing tasks always wait for a returned message. Moreover it
 * inheredits the highest priority of any rpcxing task waiting on the receive
 * queue. The receiving task will then recover its priority as explained in
 * rt_returnx. Otherwise the caller task is blocked waiting for any message to
 * be sentx/rpcxed.
 *
 * In this case these functions return if:
 *   a sender sendxs a message and has a lower priority;
 *   any rpcxed message is received;
 * - timeout occurs;
 * - an error occurs (e.g. the sender task is killed.)
 * @param task is a pointer to a @e RT_TASK structure.
 * 
 * @param msg points to the message to be eavedropped, without receive.
 *
 * @param size size of the message to be eavedropped.
 *
 * @param len is a pointer to an integer to be set to the actual len of the
 * eavedropped message.
 *
 * @param delay is a timeout relative to the current time.
 *
 * @return a pointer to the sender task is returned upon success.<br> 
 * 0 is returned if the caller is unblocked but no message has
 * been received (e.g. the task @e task was killed before sending the
 * message.)<br>
 * A special value is returned on other failure. The errors 
 * are described below:  
 * - @b 0: the sender task was killed before sending the message;
 * - @b 0xFFFF: @e task does not refer to a valid task.
 * 
 * @note Since all the messaging functions return a task address
 * 0xFFFF could seem an inappropriate return value.  However on all
 * the CPUs RTAI runs on 0xFFFF is not an address that can be used by
 * any RTAI task, so it is should be always safe.
 */
RTAI_SYSCALL_MODE RT_TASK *rt_receivex_timed(RT_TASK *task, void *msg, int size, long *len, RTIME delay)
{
    struct mcb_t *mcb;
    if ((task = rt_receive_timed(task, (unsigned long *)&mcb, delay))) {
        DO_RCV_MSG();
        return task;
    }
    return 0;
}

/* +++++++++++++++++++++++++++++++ PROXIES ++++++++++++++++++++++++++++++++++ */

// What any proxy is supposed to do, raw RTAI implementation.
static void proxy_task(RT_TASK *me)
{
    struct proxy_t *my;
    unsigned long ret;

    my = (struct proxy_t *)me->stack_bottom;            
    while (1) {
        while (my->nmsgs) {
            atomic_dec((atomic_t *)&my->nmsgs);
            rt_rpc(my->receiver, *((unsigned long *)my->msg), &ret);
        }
        rt_task_suspend(me);
    }
}

// Create a raw proxy agent task.
RT_TASK *__rt_proxy_attach(void (*agent)(long), RT_TASK *task, void *msg, int nbytes, int priority)
{
    RT_TASK *proxy, *rt_current;
    struct proxy_t *my;

        rt_current = _rt_whoami();
    if (!task) {
        task = rt_current;
    }

    if (task->magic != RT_TASK_MAGIC) {
        return 0;
    }

    if (!(proxy = rt_malloc(sizeof(RT_TASK)))) {
        return 0;
    }

    if (priority == -1 && (priority = rt_current->base_priority) == RT_SCHED_LINUX_PRIORITY) {
        priority = RT_SCHED_LOWEST_PRIORITY;
    }
    if (rt_kthread_init(proxy, agent, (long)proxy, PROXY_MIN_STACK_SIZE + nbytes + sizeof(struct proxy_t), priority, 0, 0)) {
        rt_free(proxy);
        return 0;
    }

    my = (struct proxy_t *)(proxy->stack_bottom);
    my->receiver = task ;
    my->msg      = ((char *)(proxy->stack_bottom)) + sizeof(struct proxy_t);
    my->nmsgs    = 0;
    my->nbytes   = nbytes;
    if (msg && nbytes) {
        memcpy(my->msg, msg, nbytes);
    }

        // agent is at *(proxy->stack + 2)
    return proxy;
}

// Create a raw proxy task.
RTAI_SYSCALL_MODE RT_TASK *rt_proxy_attach(RT_TASK *task, void *msg, int nbytes, int prio)
{
    return __rt_proxy_attach((void *)proxy_task, task, msg, nbytes, prio);
}

// Delete a proxy task (a simplified specific rt_task_delete).
// Note: a self delete will not do the rt_free() call.
RTAI_SYSCALL_MODE int rt_proxy_detach(RT_TASK *proxy)
{
    if (!rt_task_delete(proxy)) {
        rt_free(proxy);
        return 0;
    }
    return -EINVAL;
}

// Trigger a proxy.
RTAI_SYSCALL_MODE RT_TASK *rt_trigger(RT_TASK *proxy)
{
    struct proxy_t *his;
    
    his = (struct proxy_t *)(proxy->stack_bottom);
    if (his && proxy->magic == RT_TASK_MAGIC) {
        atomic_inc((atomic_t *)&his->nmsgs);
        rt_task_resume(proxy);
        return his->receiver;
    }
    return (RT_TASK *)0;
}

#if 1 //def CONFIG_RTAI_INTERNAL_LXRT_SUPPORT

/* ++++++++++++ ANOTHER API SET FOR EXTENDED INTERTASK MESSAGES +++++++++++++++
COPYRIGHT (C) 2003  Pierre Cloutier  (pcloutier@poseidoncontrols.com)
                    Paolo Mantegazza (mantegazza@aero.polimi.it)
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */

#include <asm/uaccess.h>

#include "rtai_registry.h"
#include "rtai_msg.h"

RTAI_SYSCALL_MODE int rt_Send(pid_t pid, void *smsg, void *rmsg, size_t ssize, size_t rsize)
{
    RT_TASK *task;
    if ((task = pid2rttask(pid))) {
        MSGCB cb;
        RT_TASK *replier;
        unsigned long replylen;
        cb.cmd    = SYNCMSG;
        cb.sbuf   = smsg;
        cb.sbytes = ssize; 
        cb.rbuf   = rmsg;
        cb.rbytes = rsize;
        if (!(replier = rt_rpc(task, (unsigned long)&cb, &replylen))) {
            return -EINVAL;
        } else if (replier != task) {
            return -ESRCH;
        }
        return replylen ;
    }
    return -ESRCH;
}

RTAI_SYSCALL_MODE pid_t rt_Receive(pid_t pid, void *msg, size_t maxsize, size_t *msglen)
{
    RT_TASK *task;
    MSGCB *cb;
    if ((task = rt_receive(pid ? pid2rttask(pid) : 0, (void *)&cb))) {
        if ((pid = rttask2pid(task))) {
            *msglen = maxsize <= cb->sbytes ? maxsize : cb->sbytes; 
            if (*msglen) {
                memcpy(msg, cb->sbuf, *msglen);
            }
            return pid;
        }
        return -ESRCH;
    }
    return -EINVAL;
}

RTAI_SYSCALL_MODE pid_t rt_Creceive(pid_t pid, void *msg, size_t maxsize, size_t *msglen, RTIME delay)
{
    RT_TASK *task;
    MSGCB *cb;
    task = pid ? pid2rttask(pid) : 0;
    if (delay) {
        task = rt_receive_timed(task, (void *)&cb, delay);
    } else {
        task = rt_receive_if(task, (void *)&cb);
    }
    if (task) {
        if ((pid = rttask2pid(task))) {
            *msglen = maxsize <= cb->sbytes ? maxsize : cb->sbytes;
            if (*msglen) {
                memcpy(msg, cb->sbuf, *msglen);
            }
            return pid;
        }
        return 0;
    }
    return 0;
}

RTAI_SYSCALL_MODE int rt_Reply(pid_t pid, void *msg, size_t size)
{
    RT_TASK *task;
    if ((task = pid2rttask(pid))) {
        MSGCB *cb;
        if ((cb = (MSGCB *)task->msg)->cmd == SYNCMSG) {
            unsigned long retlen;
            RT_TASK *retask;
            if ((retlen = size <= cb->rbytes ? size : cb->rbytes)) {
                memcpy(cb->rbuf, msg, retlen);
            }
            if (!(retask = rt_return(task, retlen))) {
                return -EINVAL;
            } else if (retask != task) {
                return -ESRCH;
            }
            return 0;
        }
        return -EPERM;
    }
    return -ESRCH;
}

static void Proxy_Task(RT_TASK *me)
{
        struct proxy_t *my;
    MSGCB cb;
        unsigned long replylen;
        my = (struct proxy_t *)me->stack_bottom;
    cb.cmd    = PROXY;
    cb.sbuf   = my->msg;
    cb.sbytes = my->nbytes;
    cb.rbuf   = &replylen;
    cb.rbytes = sizeof(replylen);
        while(1) {
        while (my->nmsgs) {
            atomic_dec((atomic_t *)&my->nmsgs);
                        rt_rpc(my->receiver, (unsigned long)(&cb), &replylen);
        }
        rt_task_suspend(me);
        }
}

RTAI_SYSCALL_MODE pid_t rt_Proxy_attach(pid_t pid, void *msg, int nbytes, int prio)
{
    RT_TASK *task;
    return (task = __rt_proxy_attach((void *)Proxy_Task, pid ? pid2rttask(pid) : 0, msg, nbytes, prio)) ? (task->lnxtsk)->pid : -ENOMEM;
}

RTAI_SYSCALL_MODE int rt_Proxy_detach(pid_t pid)
{
    RT_TASK *proxy;
    if (!rt_task_delete(proxy = pid2rttask(pid))) {
        rt_free(proxy);
        return 0;
    }
    return -EINVAL;
}

RTAI_SYSCALL_MODE pid_t rt_Trigger(pid_t pid)
{
    RT_TASK *proxy;
        struct proxy_t *his;
    if ((proxy = pid2rttask(pid))) {
            his = (struct proxy_t *)(proxy->stack_bottom);
            if (his && proxy->magic == RT_TASK_MAGIC) {
                    atomic_inc((atomic_t *)&his->nmsgs);
                    rt_task_resume(proxy);
                    return rttask2pid(his->receiver);
        }
        return -EINVAL;
    }
    return -ESRCH;
}


RTAI_SYSCALL_MODE pid_t rt_Name_attach(const char *argname)
{
    RT_TASK *task;
    task = current->rtai_tskext(TSKEXT0) ? (RT_TASK *)current->rtai_tskext(TSKEXT0) : _rt_whoami();
    if (current->comm[0] != 'U' && current->comm[1] != ':') {
            rt_strncpy_from_user(task->task_name, argname, RTAI_MAX_NAME_LENGTH);
    } else {
            strncpy(task->task_name, argname, RTAI_MAX_NAME_LENGTH);
    }
        task->task_name[RTAI_MAX_NAME_LENGTH - 1] = 0;
    return strnlen(task->task_name, RTAI_MAX_NAME_LENGTH) > (RTAI_MAX_NAME_LENGTH - 1) ? -EINVAL : task->lnxtsk ? ((struct task_struct *)current->rtai_tskext(TSKEXT1))->pid : (long)task;
}

RTAI_SYSCALL_MODE pid_t rt_Name_locate(const char *arghost, const char *argname)
{
    extern RT_TASK rt_smp_linux_task[];
    int cpuid;
    RT_TASK *task;
        for (cpuid = 0; cpuid < num_online_cpus(); cpuid++) {
                task = &rt_smp_linux_task[cpuid];
                while ((task = task->next)) {
            if (!strncmp(argname, task->task_name, RTAI_MAX_NAME_LENGTH - 1)) {
                return (struct task_struct *)(task->lnxtsk) ?  ((struct task_struct *)(task->lnxtsk)->rtai_tskext(TSKEXT1))->pid : (long)task;

            }
        }
    }
    return strlen(argname) <= 6 && (task = rt_get_adr(nam2num(argname))) ? rttask2pid(task) : 0;
}

RTAI_SYSCALL_MODE int rt_Name_detach(pid_t pid)
{
    if (pid <= PID_MAX_LIMIT) {
        if (pid != ((struct task_struct *)current->rtai_tskext(TSKEXT1))->pid ) {
            return -EINVAL;
        }
            ((RT_TASK *)current->rtai_tskext(TSKEXT0))->task_name[0] = 0;
    } else {
            ((RT_TASK *)(long)pid)->task_name[0] = 0;
    }
    return 0;
}

#endif /* CONFIG_RTAI_INTERNAL_LXRT_SUPPORT */

/* +++++++++++++++++++++ INTERTASK MESSAGES ENTRIES +++++++++++++++++++++++++ */

struct rt_native_fun_entry rt_msg_entries[] = {
    { { 1, rt_send },               SENDMSG },
    { { 1, rt_send_if },                SEND_IF },
    { { 1, rt_send_until },             SEND_UNTIL },
    { { 1, rt_send_timed },             SEND_TIMED },
    { { UW1(2, 0), rt_evdrp },          EVDRP },
    { { UW1(2, 0), rt_receive },            RECEIVEMSG },
    { { UW1(2, 0), rt_receive_if },         RECEIVE_IF },
    { { UW1(2, 0), rt_receive_until },      RECEIVE_UNTIL },
    { { UW1(2, 0), rt_receive_timed },      RECEIVE_TIMED },
    { { UW1(3, 0), rt_rpc },            RPCMSG },
    { { UW1(3, 0), rt_rpc_if },         RPC_IF },
    { { UW1(3, 0), rt_rpc_until },          RPC_UNTIL },
    { { UW1(3, 0), rt_rpc_timed },          RPC_TIMED },
    { { 0, rt_isrpc },              ISRPC },
    { { 1, rt_return },             RETURNMSG },
    { { UR1(2, 4) | UW1(3, 5), rt_rpcx },       RPCX },
    { { UR1(2, 4) | UW1(3, 5), rt_rpcx_if },    RPCX_IF },
    { { UR1(2, 4) | UW1(3, 5), rt_rpcx_until }, RPCX_UNTIL },
    { { UR1(2, 4) | UW1(3, 5), rt_rpcx_timed },     RPCX_TIMED },
    { { UR1(2, 3), rt_sendx },          SENDX },
    { { UR1(2, 3), rt_sendx_if },           SENDX_IF },
    { { UR1(2, 3), rt_sendx_until },        SENDX_UNTIL },
    { { UR1(2, 3), rt_sendx_timed },        SENDX_TIMED },
    { { UR1(2, 3), rt_returnx },            RETURNX },
    { { UW1(2, 3) | UW2(4, 0), rt_evdrpx },     EVDRPX },
    { { UW1(2, 3) | UW2(4, 0), rt_receivex },   RECEIVEX },
    { { UW1(2, 3) | UW2(4, 0), rt_receivex_if },    RECEIVEX_IF },
    { { UW1(2, 3) | UW2(4, 0), rt_receivex_until }, RECEIVEX_UNTIL },
    { { UW1(2, 3) | UW2(4, 0), rt_receivex_timed }, RECEIVEX_TIMED },
    { { UR1(2, 3), rt_proxy_attach },           PROXY_ATTACH },
    { { 1, rt_proxy_detach },                   PROXY_DETACH },
    { { 1, rt_trigger },                        PROXY_TRIGGER },
    { { UR1(2, 4) | UW1(3, 5), rt_Send },       RT_SEND },
    { { UW1(2, 3) | UW2(4, 0), rt_Receive },    RT_RECEIVE },
    { { UW1(2, 3) | UW2(4, 0), rt_Creceive },   RT_CRECEIVE },
    { { UR1(2, 3), rt_Reply },          RT_REPLY },
    { { UR1(2, 3), rt_Proxy_attach },       RT_PROXY_ATTACH },
    { { 1, rt_Proxy_detach },           RT_PROXY_DETACH },
    { { 1, rt_Trigger },                RT_TRIGGER },
    { { 1, rt_Name_attach },            RT_NAME_ATTACH },
    { { 0, rt_Name_locate },            RT_NAME_LOCATE },
    { { 1, rt_Name_detach },            RT_NAME_DETACH },
    { { 0, 0 },                         000 }
};

int __rtai_msg_init (void)
{
    return set_rt_fun_entries(rt_msg_entries);
}

void __rtai_msg_exit (void)
{
    reset_rt_fun_entries(rt_msg_entries);
}

#ifndef CONFIG_RTAI_MSG_BUILTIN
module_init(__rtai_msg_init);
module_exit(__rtai_msg_exit);
#endif /* !CONFIG_RTAI_MSG_BUILTIN */

#ifdef CONFIG_KBUILD
EXPORT_SYMBOL(rt_send);
EXPORT_SYMBOL(rt_send_if);
EXPORT_SYMBOL(rt_send_until);
EXPORT_SYMBOL(rt_send_timed);
EXPORT_SYMBOL(rt_rpc);
EXPORT_SYMBOL(rt_rpc_if);
EXPORT_SYMBOL(rt_rpc_until);
EXPORT_SYMBOL(rt_rpc_timed);
EXPORT_SYMBOL(rt_isrpc);
EXPORT_SYMBOL(rt_return);
EXPORT_SYMBOL(rt_evdrp);
EXPORT_SYMBOL(rt_receive);
EXPORT_SYMBOL(rt_receive_if);
EXPORT_SYMBOL(rt_receive_until);
EXPORT_SYMBOL(rt_receive_timed);
EXPORT_SYMBOL(rt_rpcx);
EXPORT_SYMBOL(rt_rpcx_if);
EXPORT_SYMBOL(rt_rpcx_until);
EXPORT_SYMBOL(rt_rpcx_timed);
EXPORT_SYMBOL(rt_sendx);
EXPORT_SYMBOL(rt_sendx_if);
EXPORT_SYMBOL(rt_sendx_until);
EXPORT_SYMBOL(rt_sendx_timed);
EXPORT_SYMBOL(rt_returnx);
EXPORT_SYMBOL(rt_evdrpx);
EXPORT_SYMBOL(rt_receivex);
EXPORT_SYMBOL(rt_receivex_if);
EXPORT_SYMBOL(rt_receivex_until);
EXPORT_SYMBOL(rt_receivex_timed);

EXPORT_SYMBOL(__rt_proxy_attach);
EXPORT_SYMBOL(rt_proxy_attach);
EXPORT_SYMBOL(rt_proxy_detach);
EXPORT_SYMBOL(rt_trigger);

EXPORT_SYMBOL(rt_Send);
EXPORT_SYMBOL(rt_Receive);
EXPORT_SYMBOL(rt_Creceive);
EXPORT_SYMBOL(rt_Reply);
EXPORT_SYMBOL(rt_Proxy_attach);
EXPORT_SYMBOL(rt_Proxy_detach);
EXPORT_SYMBOL(rt_Trigger);
EXPORT_SYMBOL(rt_Name_attach);
EXPORT_SYMBOL(rt_Name_locate);
EXPORT_SYMBOL(rt_Name_detach);
#endif /* CONFIG_KBUILD */

---