aboutsummaryrefslogtreecommitdiffstats
path: root/os/rt/src/chcond.c
blob: 8ee07a81410363e368e89f64b51526f529c9f4b7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
/*
    ChibiOS - Copyright (C) 2006..2018 Giovanni Di Sirio.

    This file is part of ChibiOS.

    ChibiOS 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 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/>.
*/
/*
   Concepts and parts of this file have been contributed by Leon Woestenberg.
 */

/**
 * @file    chcond.c
 * @brief   Condition Variables code.
 *
 * @addtogroup condvars
 * @details This module implements the Condition Variables mechanism. Condition
 *          variables are an extensions to the mutex subsystem and cannot
 *          work alone.
 *          <h2>Operation mode</h2>
 *          The condition variable is a synchronization object meant to be
 *          used inside a zone protected by a mutex. Mutexes and condition
 *          variables together can implement a Monitor construct.
 * @pre     In order to use the condition variable APIs the @p CH_CFG_USE_CONDVARS
 *          option must be enabled in @p chconf.h.
 * @{
 */

#include "ch.h"

#if (CH_CFG_USE_CONDVARS == TRUE) || defined(__DOXYGEN__)

/*===========================================================================*/
/* Module local definitions.                                                 */
/*===========================================================================*/

/*===========================================================================*/
/* Module exported variables.                                                */
/*===========================================================================*/

/*===========================================================================*/
/* Module local types.                                                       */
/*===========================================================================*/

/*===========================================================================*/
/* Module local variables.                                                   */
/*===========================================================================*/

/*===========================================================================*/
/* Module local functions.                                                   */
/*===========================================================================*/

/*===========================================================================*/
/* Module exported functions.                                                */
/*===========================================================================*/

/**
 * @brief   Initializes s @p condition_variable_t structure.
 *
 * @param[out] cp       pointer to a @p condition_variable_t structure
 *
 * @init
 */
void chCondObjectInit(condition_variable_t *cp) {

  chDbgCheck(cp != NULL);

  queue_init(&cp->queue);
}

/**
 * @brief   Signals one thread that is waiting on the condition variable.
 *
 * @param[in] cp        pointer to the @p condition_variable_t structure
 *
 * @api
 */
void chCondSignal(condition_variable_t *cp) {

  chDbgCheck(cp != NULL);

  chSysLock();
  if (queue_notempty(&cp->queue)) {
    chSchWakeupS(queue_fifo_remove(&cp->queue), MSG_OK);
  }
  chSysUnlock();
}

/**
 * @brief   Signals one thread that is waiting on the condition variable.
 * @post    This function does not reschedule so a call to a rescheduling
 *          function must be performed before unlocking the kernel. Note that
 *          interrupt handlers always reschedule on exit so an explicit
 *          reschedule must not be performed in ISRs.
 *
 * @param[in] cp        pointer to the @p condition_variable_t structure
 *
 * @iclass
 */
void chCondSignalI(condition_variable_t *cp) {

  chDbgCheckClassI();
  chDbgCheck(cp != NULL);

  if (queue_notempty(&cp->queue)) {
    thread_t *tp = queue_fifo_remove(&cp->queue);
    tp->u.rdymsg = MSG_OK;
    (void) chSchReadyI(tp);
  }
}

/**
 * @brief   Signals all threads that are waiting on the condition variable.
 *
 * @param[in] cp        pointer to the @p condition_variable_t structure
 *
 * @api
 */
void chCondBroadcast(condition_variable_t *cp) {

  chSysLock();
  chCondBroadcastI(cp);
  chSchRescheduleS();
  chSysUnlock();
}

/**
 * @brief   Signals all threads that are waiting on the condition variable.
 * @post    This function does not reschedule so a call to a rescheduling
 *          function must be performed before unlocking the kernel. Note that
 *          interrupt handlers always reschedule on exit so an explicit
 *          reschedule must not be performed in ISRs.
 *
 * @param[in] cp        pointer to the @p condition_variable_t structure
 *
 * @iclass
 */
void chCondBroadcastI(condition_variable_t *cp) {

  chDbgCheckClassI();
  chDbgCheck(cp != NULL);

  /* Empties the condition variable queue and inserts all the threads into the
     ready list in FIFO order. The wakeup message is set to @p MSG_RESET in
     order to make a chCondBroadcast() detectable from a chCondSignal().*/
  while (queue_notempty(&cp->queue)) {
    chSchReadyI(queue_fifo_remove(&cp->queue))->u.rdymsg = MSG_RESET;
  }
}

/**
 * @brief   Waits on the condition variable releasing the mutex lock.
 * @details Releases the currently owned mutex, waits on the condition
 *          variable, and finally acquires the mutex again. All the sequence
 *          is performed atomically.
 * @pre     The invoking thread <b>must</b> have at least one owned mutex.
 *
 * @param[in] cp        pointer to the @p condition_variable_t structure
 * @return              A message specifying how the invoking thread has been
 *                      released from the condition variable.
 * @retval MSG_OK       if the condition variable has been signaled using
 *                      @p chCondSignal().
 * @retval MSG_RESET    if the condition variable has been signaled using
 *                      @p chCondBroadcast().
 *
 * @api
 */
msg_t chCondWait(condition_variable_t *cp) {
  msg_t msg;

  chSysLock();
  msg = chCondWaitS(cp);
  chSysUnlock();
  return msg;
}

/**
 * @brief   Waits on the condition variable releasing the mutex lock.
 * @details Releases the currently owned mutex, waits on the condition
 *          variable, and finally acquires the mutex again. All the sequence
 *          is performed atomically.
 * @pre     The invoking thread <b>must</b> have at least one owned mutex.
 *
 * @param[in] cp        pointer to the @p condition_variable_t structure
 * @return              A message specifying how the invoking thread has been
 *                      released from the condition variable.
 * @retval MSG_OK       if the condition variable has been signaled using
 *                      @p chCondSignal().
 * @retval MSG_RESET    if the condition variable has been signaled using
 *                      @p chCondBroadcast().
 *
 * @sclass
 */
msg_t chCondWaitS(condition_variable_t *cp) {
  thread_t *ctp = currp;
  mutex_t *mp = chMtxGetNextMutexX();
  msg_t msg;

  chDbgCheckClassS();
  chDbgCheck(cp != NULL);
  chDbgAssert(mp != NULL, "not owning a mutex");

  /* Releasing "current" mutex.*/
  chMtxUnlockS(mp);

  /* Start waiting on the condition variable, on exit the mutex is taken
     again.*/
  ctp->u.wtobjp = cp;
  queue_prio_insert(ctp, &cp->queue);
  chSchGoSleepS(CH_STATE_WTCOND);
  msg = ctp->u.rdymsg;
  chMtxLockS(mp);

  return msg;
}

#if (CH_CFG_USE_CONDVARS_TIMEOUT == TRUE) || defined(__DOXYGEN__)
/**
 * @brief   Waits on the condition variable releasing the mutex lock.
 * @details Releases the currently owned mutex, waits on the condition
 *          variable, and finally acquires the mutex again. All the sequence
 *          is performed atomically.
 * @pre     The invoking thread <b>must</b> have at least one owned mutex.
 * @pre     The configuration option @p CH_CFG_USE_CONDVARS_TIMEOUT must be enabled
 *          in order to use this function.
 * @post    Exiting the function because a timeout does not re-acquire the
 *          mutex, the mutex ownership is lost.
 *
 * @param[in] cp        pointer to the @p condition_variable_t structure
 * @param[in] timeout   the number of ticks before the operation timeouts, the
 *                      special values are handled as follow:
 *                      - @a TIME_INFINITE no timeout.
 *                      - @a TIME_IMMEDIATE this value is not allowed.
 *                      .
 * @return              A message specifying how the invoking thread has been
 *                      released from the condition variable.
 * @retval MSG_OK       if the condition variable has been signaled using
 *                      @p chCondSignal().
 * @retval MSG_RESET    if the condition variable has been signaled using
 *                      @p chCondBroadcast().
 * @retval MSG_TIMEOUT  if the condition variable has not been signaled within
 *                      the specified timeout.
 *
 * @api
 */
msg_t chCondWaitTimeout(condition_variable_t *cp, sysinterval_t timeout) {
  msg_t msg;

  chSysLock();
  msg = chCondWaitTimeoutS(cp, timeout);
  chSysUnlock();

  return msg;
}

/**
 * @brief   Waits on the condition variable releasing the mutex lock.
 * @details Releases the currently owned mutex, waits on the condition
 *          variable, and finally acquires the mutex again. All the sequence
 *          is performed atomically.
 * @pre     The invoking thread <b>must</b> have at least one owned mutex.
 * @pre     The configuration option @p CH_CFG_USE_CONDVARS_TIMEOUT must be enabled
 *          in order to use this function.
 * @post    Exiting the function because a timeout does not re-acquire the
 *          mutex, the mutex ownership is lost.
 *
 * @param[in] cp        pointer to the @p condition_variable_t structure
 * @param[in] timeout   the number of ticks before the operation timeouts, the
 *                      special values are handled as follow:
 *                      - @a TIME_INFINITE no timeout.
 *                      - @a TIME_IMMEDIATE this value is not allowed.
 *                      .
 * @return              A message specifying how the invoking thread has been
 *                      released from the condition variable.
 * @retval MSG_OK       if the condition variable has been signaled using
 *                      @p chCondSignal().
 * @retval MSG_RESET    if the condition variable has been signaled using
 *                      @p chCondBroadcast().
 * @retval MSG_TIMEOUT  if the condition variable has not been signaled within
 *                      the specified timeout.
 *
 * @sclass
 */
msg_t chCondWaitTimeoutS(condition_variable_t *cp, sysinterval_t timeout) {
  mutex_t *mp = chMtxGetNextMutexX();
  msg_t msg;

  chDbgCheckClassS();
  chDbgCheck((cp != NULL) && (timeout != TIME_IMMEDIATE));
  chDbgAssert(mp != NULL, "not owning a mutex");

  /* Releasing "current" mutex.*/
  chMtxUnlockS(mp);

  /* Start waiting on the condition variable, on exit the mutex is taken
     again.*/
  currp->u.wtobjp = cp;
  queue_prio_insert(currp, &cp->queue);
  msg = chSchGoSleepTimeoutS(CH_STATE_WTCOND, timeout);
  if (msg != MSG_TIMEOUT) {
    chMtxLockS(mp);
  }

  return msg;
}
#endif /* CH_CFG_USE_CONDVARS_TIMEOUT == TRUE */

#endif /* CH_CFG_USE_CONDVARS == TRUE */

/** @} */