msg.c

rtai-3.1-test3的源代码(Real-Time Application Interface )

/** 
 * @file
 * Message handling functions.
 * @author Paolo Mantegazza
 *
 * @note Copyright (C) 1999-2003 Paolo Mantegazza
 * <[e-mail]> [ 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 <rtai_schedcore.h>

MODULE_LICENSE("GPL");

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

/* +++++++++++++++++++++++++++++ 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.
 */
RT_TASK *rt_send(RT_TASK *task, unsigned int msg)
{
	DECLARE_RT_CURRENT;
	unsigned long flags;

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

	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 = NOTHING;
		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;
		rem_ready_current(rt_current);
		rt_schedule();
	}
	if (rt_current->msg_queue.task != rt_current) {
		rt_current->msg_queue.task = rt_current;
		task = (RT_TASK *)0;
	}
	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)
 */
RT_TASK *rt_send_if(RT_TASK *task, unsigned int msg)
{
	DECLARE_RT_CURRENT;
	unsigned long flags;

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

	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 = NOTHING;
		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 = (RT_TASK *)0;
		}
	} else {
		task = (RT_TASK *)0;
	}
	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.
 */
RT_TASK *rt_send_until(RT_TASK *task, unsigned int msg, RTIME time)
{
	DECLARE_RT_CURRENT;
	unsigned long flags;

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

	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 = NOTHING;
		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);
			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) {
		dequeue_blocked(rt_current);
		rt_current->msg_queue.task = rt_current;
		task = (RT_TASK *)0;
	}
	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)
 */

RT_TASK *rt_send_timed(RT_TASK *task, unsigned int 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.
 */
RT_TASK *rt_rpc(RT_TASK *task, unsigned int to_do, unsigned int *result)
{

	DECLARE_RT_CURRENT;
	unsigned long flags;

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

	flags = rt_global_save_flags_and_cli();
	ASSIGN_RT_CURRENT;
	if ((task->state & RT_SCHED_RECEIVE) &&