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/*
ChibiOS/RT - Copyright (C) 2006,2007,2008,2009,2010 Giovanni Di Sirio.
This file is part of ChibiOS/RT.
ChibiOS/RT 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 3 of the License, or
(at your option) any later version.
ChibiOS/RT 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, see <http://www.gnu.org/licenses/>.
*/
/**
* @file chmsg.c
* @brief Messages code.
*
* @addtogroup messages
* @details Synchronous inter-thread messages APIs and services.
* <h2>Operation Mode</h2>
* Synchronous messages are an easy to use and fast IPC mechanism,
* threads can both act as message servers and/or message clients,
* the mechanism allows data to be carried in both directions. Note
* that messages are not copied between the client and server threads
* but just a pointer passed so the exchange is very time
* efficient.<br>
* Messages are scalar data types of type @p msg_t that are guaranteed
* to be size compatible with data pointers. Note that on some
* architectures function pointers can be larger that @p msg_t.<br>
* Messages are usually processed in FIFO order but it is possible to
* process them in priority order by enabling the
* @p CH_USE_MESSAGES_PRIORITY option in @p chconf.h.<br>
* @pre In order to use the message APIs the @p CH_USE_MESSAGES option
* must be enabled in @p chconf.h.
* @post Enabling messages requires 6-12 (depending on the architecture)
* extra bytes in the @p Thread structure.
* @{
*/
#include "ch.h"
#if CH_USE_MESSAGES || defined(__DOXYGEN__)
#if CH_USE_MESSAGES_PRIORITY
#define msg_insert(tp, qp) prio_insert(tp, qp)
#else
#define msg_insert(tp, qp) queue_insert(tp, qp)
#endif
/**
* @brief Sends a message to the specified thread.
* @details The sender is stopped until the receiver executes a
* @p chMsgRelease()after receiving the message.
*
* @param[in] tp the pointer to the thread
* @param[in] msg the message
* @return The answer message from @p chMsgRelease().
*
* @api
*/
msg_t chMsgSend(Thread *tp, msg_t msg) {
Thread *ctp = currp;
chDbgCheck(tp != NULL, "chMsgSend");
chSysLock();
ctp->p_msg = msg;
ctp->p_u.wtobjp = &tp->p_msgqueue;
msg_insert(ctp, &tp->p_msgqueue);
if (tp->p_state == THD_STATE_WTMSG)
chSchReadyI(tp);
chSchGoSleepS(THD_STATE_SNDMSG);
msg = ctp->p_u.rdymsg;
chSysUnlock();
return msg;
}
/**
* @brief Suspends the thread and waits for an incoming message.
* @post After receiving a message the function @p chMsgRelease() must be
* invoked in order to acknowledge the reception and send the answer.
* @note If the message is a pointer then you can assume that the data
* pointed by the message is stable until you invoke @p chMsgRelease()
* because the sending thread is suspended until then.
*
* @return The message.
*
* @api
*/
msg_t chMsgWait(void) {
msg_t msg;
chSysLock();
if (!chMsgIsPendingI(currp))
chSchGoSleepS(THD_STATE_WTMSG);
#if defined(CH_ARCHITECTURE_STM8)
msg = chMsgGetI((volatile Thread *)currp); /* Temporary hack.*/
#else
msg = chMsgGetI(currp);
#endif
chSysUnlock();
return msg;
}
/**
* @brief Returns the next message in the queue.
* @post After receiving a message the function @p chMsgRelease() must be
* invoked in order to acknowledge the reception and send the answer.
* @note If the message is a pointer then you can assume that the data
* pointed by the message is stable until you invoke @p chMsgRelease()
* because the sending thread is suspended until then.
*
* @return The message.
* @retval 0 if the queue is empty.
*
* @api
*/
msg_t chMsgGet(void) {
msg_t msg;
chSysLock();
msg = chMsgIsPendingI(currp) ? chMsgGetI(currp) : (msg_t)NULL;
chSysUnlock();
return msg;
}
/**
* @brief Releases the thread waiting on top of the messages queue.
* @pre Invoke this function only after a message has been received
* using @p chMsgWait() or @p chMsgGet().
*
* @param[in] msg the message returned to the message sender
*
* @api
*/
void chMsgRelease(msg_t msg) {
chSysLock();
chDbgAssert(chMsgIsPendingI(currp),
"chMsgRelease(), #1",
"no message pending");
chSchWakeupS(fifo_remove(&currp->p_msgqueue), msg);
chSysUnlock();
}
#endif /* CH_USE_MESSAGES */
/** @} */
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