Outline ![]()
Files ![]()
loading...
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
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
/*
* FreeRTOS Kernel V10.3.1
* Copyright (C) 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
* http://www.FreeRTOS.org
* http://aws.amazon.com/freertos
*
* 1 tab == 4 spaces!
*/
#ifndef SEMAPHORE_H
#define SEMAPHORE_H
#ifndef INC_FREERTOS_H
#error "include FreeRTOS.h" must appear in source files before "include semphr.h"
#endif
#include "queue.h"
typedef QueueHandle_t SemaphoreHandle_t;
#define semBINARY_SEMAPHORE_QUEUE_LENGTH ( ( uint8_t ) 1U )
#define semSEMAPHORE_QUEUE_ITEM_LENGTH ( ( uint8_t ) 0U )
#define semGIVE_BLOCK_TIME ( ( TickType_t ) 0U )
/**
* semphr. h
* <pre>vSemaphoreCreateBinary( SemaphoreHandle_t xSemaphore )</pre>
*
* In many usage scenarios it is faster and more memory efficient to use a
* direct to task notification in place of a binary semaphore!
* http://www.freertos.org/RTOS-task-notifications.html
*
* This old vSemaphoreCreateBinary() macro is now deprecated in favour of the
* xSemaphoreCreateBinary() function. Note that binary semaphores created using
* the vSemaphoreCreateBinary() macro are created in a state such that the
* first call to 'take' the semaphore would pass, whereas binary semaphores
* created using xSemaphoreCreateBinary() are created in a state such that the
* the semaphore must first be 'given' before it can be 'taken'.
*
* <i>Macro</i> that implements a semaphore by using the existing queue mechanism.
* The queue length is 1 as this is a binary semaphore. The data size is 0
* as we don't want to actually store any data - we just want to know if the
* queue is empty or full.
*
* This type of semaphore can be used for pure synchronisation between tasks or
* between an interrupt and a task. The semaphore need not be given back once
* obtained, so one task/interrupt can continuously 'give' the semaphore while
* another continuously 'takes' the semaphore. For this reason this type of
* semaphore does not use a priority inheritance mechanism. For an alternative
* that does use priority inheritance see xSemaphoreCreateMutex().
*
* @param xSemaphore Handle to the created semaphore. Should be of type SemaphoreHandle_t.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore = NULL;
void vATask( void * pvParameters )
{
// Semaphore cannot be used before a call to vSemaphoreCreateBinary ().
// This is a macro so pass the variable in directly.
vSemaphoreCreateBinary( xSemaphore );
if( xSemaphore != NULL )
{
// The semaphore was created successfully.
// The semaphore can now be used.
}
}
</pre>
* \defgroup vSemaphoreCreateBinary vSemaphoreCreateBinary
* \ingroup Semaphores
*/
#if( configSUPPORT_DYNAMIC_ALLOCATION == 1 )
#define vSemaphoreCreateBinary( xSemaphore ) \
{ \
( xSemaphore ) = xQueueGenericCreate( ( UBaseType_t ) 1, semSEMAPHORE_QUEUE_ITEM_LENGTH, queueQUEUE_TYPE_BINARY_SEMAPHORE ); \
if( ( xSemaphore ) != NULL ) \
{ \
( void ) xSemaphoreGive( ( xSemaphore ) ); \
} \
}
#endif
/**
* semphr. h
* <pre>SemaphoreHandle_t xSemaphoreCreateBinary( void )</pre>
*
* Creates a new binary semaphore instance, and returns a handle by which the
* new semaphore can be referenced.
*
* In many usage scenarios it is faster and more memory efficient to use a
* direct to task notification in place of a binary semaphore!
* http://www.freertos.org/RTOS-task-notifications.html
*
* Internally, within the FreeRTOS implementation, binary semaphores use a block
* of memory, in which the semaphore structure is stored. If a binary semaphore
* is created using xSemaphoreCreateBinary() then the required memory is
* automatically dynamically allocated inside the xSemaphoreCreateBinary()
* function. (see http://www.freertos.org/a00111.html). If a binary semaphore
* is created using xSemaphoreCreateBinaryStatic() then the application writer
* must provide the memory. xSemaphoreCreateBinaryStatic() therefore allows a
* binary semaphore to be created without using any dynamic memory allocation.
*
* The old vSemaphoreCreateBinary() macro is now deprecated in favour of this
* xSemaphoreCreateBinary() function. Note that binary semaphores created using
* the vSemaphoreCreateBinary() macro are created in a state such that the
* first call to 'take' the semaphore would pass, whereas binary semaphores
* created using xSemaphoreCreateBinary() are created in a state such that the
* the semaphore must first be 'given' before it can be 'taken'.
*
* This type of semaphore can be used for pure synchronisation between tasks or
* between an interrupt and a task. The semaphore need not be given back once
* obtained, so one task/interrupt can continuously 'give' the semaphore while
* another continuously 'takes' the semaphore. For this reason this type of
* semaphore does not use a priority inheritance mechanism. For an alternative
* that does use priority inheritance see xSemaphoreCreateMutex().
*
* @return Handle to the created semaphore, or NULL if the memory required to
* hold the semaphore's data structures could not be allocated.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore = NULL;
void vATask( void * pvParameters )
{
// Semaphore cannot be used before a call to xSemaphoreCreateBinary().
// This is a macro so pass the variable in directly.
xSemaphore = xSemaphoreCreateBinary();
if( xSemaphore != NULL )
{
// The semaphore was created successfully.
// The semaphore can now be used.
}
}
</pre>
* \defgroup xSemaphoreCreateBinary xSemaphoreCreateBinary
* \ingroup Semaphores
*/
#if( configSUPPORT_DYNAMIC_ALLOCATION == 1 )
#define xSemaphoreCreateBinary() xQueueGenericCreate( ( UBaseType_t ) 1, semSEMAPHORE_QUEUE_ITEM_LENGTH, queueQUEUE_TYPE_BINARY_SEMAPHORE )
#endif
/**
* semphr. h
* <pre>SemaphoreHandle_t xSemaphoreCreateBinaryStatic( StaticSemaphore_t *pxSemaphoreBuffer )</pre>
*
* Creates a new binary semaphore instance, and returns a handle by which the
* new semaphore can be referenced.
*
* NOTE: In many usage scenarios it is faster and more memory efficient to use a
* direct to task notification in place of a binary semaphore!
* http://www.freertos.org/RTOS-task-notifications.html
*
* Internally, within the FreeRTOS implementation, binary semaphores use a block
* of memory, in which the semaphore structure is stored. If a binary semaphore
* is created using xSemaphoreCreateBinary() then the required memory is
* automatically dynamically allocated inside the xSemaphoreCreateBinary()
* function. (see http://www.freertos.org/a00111.html). If a binary semaphore
* is created using xSemaphoreCreateBinaryStatic() then the application writer
* must provide the memory. xSemaphoreCreateBinaryStatic() therefore allows a
* binary semaphore to be created without using any dynamic memory allocation.
*
* This type of semaphore can be used for pure synchronisation between tasks or
* between an interrupt and a task. The semaphore need not be given back once
* obtained, so one task/interrupt can continuously 'give' the semaphore while
* another continuously 'takes' the semaphore. For this reason this type of
* semaphore does not use a priority inheritance mechanism. For an alternative
* that does use priority inheritance see xSemaphoreCreateMutex().
*
* @param pxSemaphoreBuffer Must point to a variable of type StaticSemaphore_t,
* which will then be used to hold the semaphore's data structure, removing the
* need for the memory to be allocated dynamically.
*
* @return If the semaphore is created then a handle to the created semaphore is
* returned. If pxSemaphoreBuffer is NULL then NULL is returned.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore = NULL;
StaticSemaphore_t xSemaphoreBuffer;
void vATask( void * pvParameters )
{
// Semaphore cannot be used before a call to xSemaphoreCreateBinary().
// The semaphore's data structures will be placed in the xSemaphoreBuffer
// variable, the address of which is passed into the function. The
// function's parameter is not NULL, so the function will not attempt any
// dynamic memory allocation, and therefore the function will not return
// return NULL.
xSemaphore = xSemaphoreCreateBinary( &xSemaphoreBuffer );
// Rest of task code goes here.
}
</pre>
* \defgroup xSemaphoreCreateBinaryStatic xSemaphoreCreateBinaryStatic
* \ingroup Semaphores
*/
#if( configSUPPORT_STATIC_ALLOCATION == 1 )
#define xSemaphoreCreateBinaryStatic( pxStaticSemaphore ) xQueueGenericCreateStatic( ( UBaseType_t ) 1, semSEMAPHORE_QUEUE_ITEM_LENGTH, NULL, pxStaticSemaphore, queueQUEUE_TYPE_BINARY_SEMAPHORE )
#endif /* configSUPPORT_STATIC_ALLOCATION */
/**
* semphr. h
* <pre>xSemaphoreTake(
* SemaphoreHandle_t xSemaphore,
* TickType_t xBlockTime
* )</pre>
*
* <i>Macro</i> to obtain a semaphore. The semaphore must have previously been
* created with a call to xSemaphoreCreateBinary(), xSemaphoreCreateMutex() or
* xSemaphoreCreateCounting().
*
* @param xSemaphore A handle to the semaphore being taken - obtained when
* the semaphore was created.
*
* @param xBlockTime The time in ticks to wait for the semaphore to become
* available. The macro portTICK_PERIOD_MS can be used to convert this to a
* real time. A block time of zero can be used to poll the semaphore. A block
* time of portMAX_DELAY can be used to block indefinitely (provided
* INCLUDE_vTaskSuspend is set to 1 in FreeRTOSConfig.h).
*
* @return pdTRUE if the semaphore was obtained. pdFALSE
* if xBlockTime expired without the semaphore becoming available.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore = NULL;
// A task that creates a semaphore.
void vATask( void * pvParameters )
{
// Create the semaphore to guard a shared resource.
xSemaphore = xSemaphoreCreateBinary();
}
// A task that uses the semaphore.
void vAnotherTask( void * pvParameters )
{
// ... Do other things.
if( xSemaphore != NULL )
{
// See if we can obtain the semaphore. If the semaphore is not available
// wait 10 ticks to see if it becomes free.
if( xSemaphoreTake( xSemaphore, ( TickType_t ) 10 ) == pdTRUE )
{
// We were able to obtain the semaphore and can now access the
// shared resource.
// ...
// We have finished accessing the shared resource. Release the
// semaphore.
xSemaphoreGive( xSemaphore );
}
else
{
// We could not obtain the semaphore and can therefore not access
// the shared resource safely.
}
}
}
</pre>
* \defgroup xSemaphoreTake xSemaphoreTake
* \ingroup Semaphores
*/
#define xSemaphoreTake( xSemaphore, xBlockTime ) xQueueSemaphoreTake( ( xSemaphore ), ( xBlockTime ) )
/**
* semphr. h
* xSemaphoreTakeRecursive(
* SemaphoreHandle_t xMutex,
* TickType_t xBlockTime
* )
*
* <i>Macro</i> to recursively obtain, or 'take', a mutex type semaphore.
* The mutex must have previously been created using a call to
* xSemaphoreCreateRecursiveMutex();
*
* configUSE_RECURSIVE_MUTEXES must be set to 1 in FreeRTOSConfig.h for this
* macro to be available.
*
* This macro must not be used on mutexes created using xSemaphoreCreateMutex().
*
* A mutex used recursively can be 'taken' repeatedly by the owner. The mutex
* doesn't become available again until the owner has called
* xSemaphoreGiveRecursive() for each successful 'take' request. For example,
* if a task successfully 'takes' the same mutex 5 times then the mutex will
* not be available to any other task until it has also 'given' the mutex back
* exactly five times.
*
* @param xMutex A handle to the mutex being obtained. This is the
* handle returned by xSemaphoreCreateRecursiveMutex();
*
* @param xBlockTime The time in ticks to wait for the semaphore to become
* available. The macro portTICK_PERIOD_MS can be used to convert this to a
* real time. A block time of zero can be used to poll the semaphore. If
* the task already owns the semaphore then xSemaphoreTakeRecursive() will
* return immediately no matter what the value of xBlockTime.
*
* @return pdTRUE if the semaphore was obtained. pdFALSE if xBlockTime
* expired without the semaphore becoming available.
*
* Example usage:
<pre>
SemaphoreHandle_t xMutex = NULL;
// A task that creates a mutex.
void vATask( void * pvParameters )
{
// Create the mutex to guard a shared resource.
xMutex = xSemaphoreCreateRecursiveMutex();
}
// A task that uses the mutex.
void vAnotherTask( void * pvParameters )
{
// ... Do other things.
if( xMutex != NULL )
{
// See if we can obtain the mutex. If the mutex is not available
// wait 10 ticks to see if it becomes free.
if( xSemaphoreTakeRecursive( xSemaphore, ( TickType_t ) 10 ) == pdTRUE )
{
// We were able to obtain the mutex and can now access the
// shared resource.
// ...
// For some reason due to the nature of the code further calls to
// xSemaphoreTakeRecursive() are made on the same mutex. In real
// code these would not be just sequential calls as this would make
// no sense. Instead the calls are likely to be buried inside
// a more complex call structure.
xSemaphoreTakeRecursive( xMutex, ( TickType_t ) 10 );
xSemaphoreTakeRecursive( xMutex, ( TickType_t ) 10 );
// The mutex has now been 'taken' three times, so will not be
// available to another task until it has also been given back
// three times. Again it is unlikely that real code would have
// these calls sequentially, but instead buried in a more complex
// call structure. This is just for illustrative purposes.
xSemaphoreGiveRecursive( xMutex );
xSemaphoreGiveRecursive( xMutex );
xSemaphoreGiveRecursive( xMutex );
// Now the mutex can be taken by other tasks.
}
else
{
// We could not obtain the mutex and can therefore not access
// the shared resource safely.
}
}
}
</pre>
* \defgroup xSemaphoreTakeRecursive xSemaphoreTakeRecursive
* \ingroup Semaphores
*/
#if( configUSE_RECURSIVE_MUTEXES == 1 )
#define xSemaphoreTakeRecursive( xMutex, xBlockTime ) xQueueTakeMutexRecursive( ( xMutex ), ( xBlockTime ) )
#endif
/**
* semphr. h
* <pre>xSemaphoreGive( SemaphoreHandle_t xSemaphore )</pre>
*
* <i>Macro</i> to release a semaphore. The semaphore must have previously been
* created with a call to xSemaphoreCreateBinary(), xSemaphoreCreateMutex() or
* xSemaphoreCreateCounting(). and obtained using sSemaphoreTake().
*
* This macro must not be used from an ISR. See xSemaphoreGiveFromISR () for
* an alternative which can be used from an ISR.
*
* This macro must also not be used on semaphores created using
* xSemaphoreCreateRecursiveMutex().
*
* @param xSemaphore A handle to the semaphore being released. This is the
* handle returned when the semaphore was created.
*
* @return pdTRUE if the semaphore was released. pdFALSE if an error occurred.
* Semaphores are implemented using queues. An error can occur if there is
* no space on the queue to post a message - indicating that the
* semaphore was not first obtained correctly.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore = NULL;
void vATask( void * pvParameters )
{
// Create the semaphore to guard a shared resource.
xSemaphore = vSemaphoreCreateBinary();
if( xSemaphore != NULL )
{
if( xSemaphoreGive( xSemaphore ) != pdTRUE )
{
// We would expect this call to fail because we cannot give
// a semaphore without first "taking" it!
}
// Obtain the semaphore - don't block if the semaphore is not
// immediately available.
if( xSemaphoreTake( xSemaphore, ( TickType_t ) 0 ) )
{
// We now have the semaphore and can access the shared resource.
// ...
// We have finished accessing the shared resource so can free the
// semaphore.
if( xSemaphoreGive( xSemaphore ) != pdTRUE )
{
// We would not expect this call to fail because we must have
// obtained the semaphore to get here.
}
}
}
}
</pre>
* \defgroup xSemaphoreGive xSemaphoreGive
* \ingroup Semaphores
*/
#define xSemaphoreGive( xSemaphore ) xQueueGenericSend( ( QueueHandle_t ) ( xSemaphore ), NULL, semGIVE_BLOCK_TIME, queueSEND_TO_BACK )
/**
* semphr. h
* <pre>xSemaphoreGiveRecursive( SemaphoreHandle_t xMutex )</pre>
*
* <i>Macro</i> to recursively release, or 'give', a mutex type semaphore.
* The mutex must have previously been created using a call to
* xSemaphoreCreateRecursiveMutex();
*
* configUSE_RECURSIVE_MUTEXES must be set to 1 in FreeRTOSConfig.h for this
* macro to be available.
*
* This macro must not be used on mutexes created using xSemaphoreCreateMutex().
*
* A mutex used recursively can be 'taken' repeatedly by the owner. The mutex
* doesn't become available again until the owner has called
* xSemaphoreGiveRecursive() for each successful 'take' request. For example,
* if a task successfully 'takes' the same mutex 5 times then the mutex will
* not be available to any other task until it has also 'given' the mutex back
* exactly five times.
*
* @param xMutex A handle to the mutex being released, or 'given'. This is the
* handle returned by xSemaphoreCreateMutex();
*
* @return pdTRUE if the semaphore was given.
*
* Example usage:
<pre>
SemaphoreHandle_t xMutex = NULL;
// A task that creates a mutex.
void vATask( void * pvParameters )
{
// Create the mutex to guard a shared resource.
xMutex = xSemaphoreCreateRecursiveMutex();
}
// A task that uses the mutex.
void vAnotherTask( void * pvParameters )
{
// ... Do other things.
if( xMutex != NULL )
{
// See if we can obtain the mutex. If the mutex is not available
// wait 10 ticks to see if it becomes free.
if( xSemaphoreTakeRecursive( xMutex, ( TickType_t ) 10 ) == pdTRUE )
{
// We were able to obtain the mutex and can now access the
// shared resource.
// ...
// For some reason due to the nature of the code further calls to
// xSemaphoreTakeRecursive() are made on the same mutex. In real
// code these would not be just sequential calls as this would make
// no sense. Instead the calls are likely to be buried inside
// a more complex call structure.
xSemaphoreTakeRecursive( xMutex, ( TickType_t ) 10 );
xSemaphoreTakeRecursive( xMutex, ( TickType_t ) 10 );
// The mutex has now been 'taken' three times, so will not be
// available to another task until it has also been given back
// three times. Again it is unlikely that real code would have
// these calls sequentially, it would be more likely that the calls
// to xSemaphoreGiveRecursive() would be called as a call stack
// unwound. This is just for demonstrative purposes.
xSemaphoreGiveRecursive( xMutex );
xSemaphoreGiveRecursive( xMutex );
xSemaphoreGiveRecursive( xMutex );
// Now the mutex can be taken by other tasks.
}
else
{
// We could not obtain the mutex and can therefore not access
// the shared resource safely.
}
}
}
</pre>
* \defgroup xSemaphoreGiveRecursive xSemaphoreGiveRecursive
* \ingroup Semaphores
*/
#if( configUSE_RECURSIVE_MUTEXES == 1 )
#define xSemaphoreGiveRecursive( xMutex ) xQueueGiveMutexRecursive( ( xMutex ) )
#endif
/**
* semphr. h
* <pre>
xSemaphoreGiveFromISR(
SemaphoreHandle_t xSemaphore,
BaseType_t *pxHigherPriorityTaskWoken
)</pre>
*
* <i>Macro</i> to release a semaphore. The semaphore must have previously been
* created with a call to xSemaphoreCreateBinary() or xSemaphoreCreateCounting().
*
* Mutex type semaphores (those created using a call to xSemaphoreCreateMutex())
* must not be used with this macro.
*
* This macro can be used from an ISR.
*
* @param xSemaphore A handle to the semaphore being released. This is the
* handle returned when the semaphore was created.
*
* @param pxHigherPriorityTaskWoken xSemaphoreGiveFromISR() will set
* *pxHigherPriorityTaskWoken to pdTRUE if giving the semaphore caused a task
* to unblock, and the unblocked task has a priority higher than the currently
* running task. If xSemaphoreGiveFromISR() sets this value to pdTRUE then
* a context switch should be requested before the interrupt is exited.
*
* @return pdTRUE if the semaphore was successfully given, otherwise errQUEUE_FULL.
*
* Example usage:
<pre>
\#define LONG_TIME 0xffff
\#define TICKS_TO_WAIT 10
SemaphoreHandle_t xSemaphore = NULL;
// Repetitive task.
void vATask( void * pvParameters )
{
for( ;; )
{
// We want this task to run every 10 ticks of a timer. The semaphore
// was created before this task was started.
// Block waiting for the semaphore to become available.
if( xSemaphoreTake( xSemaphore, LONG_TIME ) == pdTRUE )
{
// It is time to execute.
// ...
// We have finished our task. Return to the top of the loop where
// we will block on the semaphore until it is time to execute
// again. Note when using the semaphore for synchronisation with an
// ISR in this manner there is no need to 'give' the semaphore back.
}
}
}
// Timer ISR
void vTimerISR( void * pvParameters )
{
static uint8_t ucLocalTickCount = 0;
static BaseType_t xHigherPriorityTaskWoken;
// A timer tick has occurred.
// ... Do other time functions.
// Is it time for vATask () to run?
xHigherPriorityTaskWoken = pdFALSE;
ucLocalTickCount++;
if( ucLocalTickCount >= TICKS_TO_WAIT )
{
// Unblock the task by releasing the semaphore.
xSemaphoreGiveFromISR( xSemaphore, &xHigherPriorityTaskWoken );
// Reset the count so we release the semaphore again in 10 ticks time.
ucLocalTickCount = 0;
}
if( xHigherPriorityTaskWoken != pdFALSE )
{
// We can force a context switch here. Context switching from an
// ISR uses port specific syntax. Check the demo task for your port
// to find the syntax required.
}
}
</pre>
* \defgroup xSemaphoreGiveFromISR xSemaphoreGiveFromISR
* \ingroup Semaphores
*/
#define xSemaphoreGiveFromISR( xSemaphore, pxHigherPriorityTaskWoken ) xQueueGiveFromISR( ( QueueHandle_t ) ( xSemaphore ), ( pxHigherPriorityTaskWoken ) )
/**
* semphr. h
* <pre>
xSemaphoreTakeFromISR(
SemaphoreHandle_t xSemaphore,
BaseType_t *pxHigherPriorityTaskWoken
)</pre>
*
* <i>Macro</i> to take a semaphore from an ISR. The semaphore must have
* previously been created with a call to xSemaphoreCreateBinary() or
* xSemaphoreCreateCounting().
*
* Mutex type semaphores (those created using a call to xSemaphoreCreateMutex())
* must not be used with this macro.
*
* This macro can be used from an ISR, however taking a semaphore from an ISR
* is not a common operation. It is likely to only be useful when taking a
* counting semaphore when an interrupt is obtaining an object from a resource
* pool (when the semaphore count indicates the number of resources available).
*
* @param xSemaphore A handle to the semaphore being taken. This is the
* handle returned when the semaphore was created.
*
* @param pxHigherPriorityTaskWoken xSemaphoreTakeFromISR() will set
* *pxHigherPriorityTaskWoken to pdTRUE if taking the semaphore caused a task
* to unblock, and the unblocked task has a priority higher than the currently
* running task. If xSemaphoreTakeFromISR() sets this value to pdTRUE then
* a context switch should be requested before the interrupt is exited.
*
* @return pdTRUE if the semaphore was successfully taken, otherwise
* pdFALSE
*/
#define xSemaphoreTakeFromISR( xSemaphore, pxHigherPriorityTaskWoken ) xQueueReceiveFromISR( ( QueueHandle_t ) ( xSemaphore ), NULL, ( pxHigherPriorityTaskWoken ) )
/**
* semphr. h
* <pre>SemaphoreHandle_t xSemaphoreCreateMutex( void )</pre>
*
* Creates a new mutex type semaphore instance, and returns a handle by which
* the new mutex can be referenced.
*
* Internally, within the FreeRTOS implementation, mutex semaphores use a block
* of memory, in which the mutex structure is stored. If a mutex is created
* using xSemaphoreCreateMutex() then the required memory is automatically
* dynamically allocated inside the xSemaphoreCreateMutex() function. (see
* http://www.freertos.org/a00111.html). If a mutex is created using
* xSemaphoreCreateMutexStatic() then the application writer must provided the
* memory. xSemaphoreCreateMutexStatic() therefore allows a mutex to be created
* without using any dynamic memory allocation.
*
* Mutexes created using this function can be accessed using the xSemaphoreTake()
* and xSemaphoreGive() macros. The xSemaphoreTakeRecursive() and
* xSemaphoreGiveRecursive() macros must not be used.
*
* This type of semaphore uses a priority inheritance mechanism so a task
* 'taking' a semaphore MUST ALWAYS 'give' the semaphore back once the
* semaphore it is no longer required.
*
* Mutex type semaphores cannot be used from within interrupt service routines.
*
* See xSemaphoreCreateBinary() for an alternative implementation that can be
* used for pure synchronisation (where one task or interrupt always 'gives' the
* semaphore and another always 'takes' the semaphore) and from within interrupt
* service routines.
*
* @return If the mutex was successfully created then a handle to the created
* semaphore is returned. If there was not enough heap to allocate the mutex
* data structures then NULL is returned.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore;
void vATask( void * pvParameters )
{
// Semaphore cannot be used before a call to xSemaphoreCreateMutex().
// This is a macro so pass the variable in directly.
xSemaphore = xSemaphoreCreateMutex();
if( xSemaphore != NULL )
{
// The semaphore was created successfully.
// The semaphore can now be used.
}
}
</pre>
* \defgroup xSemaphoreCreateMutex xSemaphoreCreateMutex
* \ingroup Semaphores
*/
#if( configSUPPORT_DYNAMIC_ALLOCATION == 1 )
#define xSemaphoreCreateMutex() xQueueCreateMutex( queueQUEUE_TYPE_MUTEX )
#endif
/**
* semphr. h
* <pre>SemaphoreHandle_t xSemaphoreCreateMutexStatic( StaticSemaphore_t *pxMutexBuffer )</pre>
*
* Creates a new mutex type semaphore instance, and returns a handle by which
* the new mutex can be referenced.
*
* Internally, within the FreeRTOS implementation, mutex semaphores use a block
* of memory, in which the mutex structure is stored. If a mutex is created
* using xSemaphoreCreateMutex() then the required memory is automatically
* dynamically allocated inside the xSemaphoreCreateMutex() function. (see
* http://www.freertos.org/a00111.html). If a mutex is created using
* xSemaphoreCreateMutexStatic() then the application writer must provided the
* memory. xSemaphoreCreateMutexStatic() therefore allows a mutex to be created
* without using any dynamic memory allocation.
*
* Mutexes created using this function can be accessed using the xSemaphoreTake()
* and xSemaphoreGive() macros. The xSemaphoreTakeRecursive() and
* xSemaphoreGiveRecursive() macros must not be used.
*
* This type of semaphore uses a priority inheritance mechanism so a task
* 'taking' a semaphore MUST ALWAYS 'give' the semaphore back once the
* semaphore it is no longer required.
*
* Mutex type semaphores cannot be used from within interrupt service routines.
*
* See xSemaphoreCreateBinary() for an alternative implementation that can be
* used for pure synchronisation (where one task or interrupt always 'gives' the
* semaphore and another always 'takes' the semaphore) and from within interrupt
* service routines.
*
* @param pxMutexBuffer Must point to a variable of type StaticSemaphore_t,
* which will be used to hold the mutex's data structure, removing the need for
* the memory to be allocated dynamically.
*
* @return If the mutex was successfully created then a handle to the created
* mutex is returned. If pxMutexBuffer was NULL then NULL is returned.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore;
StaticSemaphore_t xMutexBuffer;
void vATask( void * pvParameters )
{
// A mutex cannot be used before it has been created. xMutexBuffer is
// into xSemaphoreCreateMutexStatic() so no dynamic memory allocation is
// attempted.
xSemaphore = xSemaphoreCreateMutexStatic( &xMutexBuffer );
// As no dynamic memory allocation was performed, xSemaphore cannot be NULL,
// so there is no need to check it.
}
</pre>
* \defgroup xSemaphoreCreateMutexStatic xSemaphoreCreateMutexStatic
* \ingroup Semaphores
*/
#if( configSUPPORT_STATIC_ALLOCATION == 1 )
#define xSemaphoreCreateMutexStatic( pxMutexBuffer ) xQueueCreateMutexStatic( queueQUEUE_TYPE_MUTEX, ( pxMutexBuffer ) )
#endif /* configSUPPORT_STATIC_ALLOCATION */
/**
* semphr. h
* <pre>SemaphoreHandle_t xSemaphoreCreateRecursiveMutex( void )</pre>
*
* Creates a new recursive mutex type semaphore instance, and returns a handle
* by which the new recursive mutex can be referenced.
*
* Internally, within the FreeRTOS implementation, recursive mutexs use a block
* of memory, in which the mutex structure is stored. If a recursive mutex is
* created using xSemaphoreCreateRecursiveMutex() then the required memory is
* automatically dynamically allocated inside the
* xSemaphoreCreateRecursiveMutex() function. (see
* http://www.freertos.org/a00111.html). If a recursive mutex is created using
* xSemaphoreCreateRecursiveMutexStatic() then the application writer must
* provide the memory that will get used by the mutex.
* xSemaphoreCreateRecursiveMutexStatic() therefore allows a recursive mutex to
* be created without using any dynamic memory allocation.
*
* Mutexes created using this macro can be accessed using the
* xSemaphoreTakeRecursive() and xSemaphoreGiveRecursive() macros. The
* xSemaphoreTake() and xSemaphoreGive() macros must not be used.
*
* A mutex used recursively can be 'taken' repeatedly by the owner. The mutex
* doesn't become available again until the owner has called
* xSemaphoreGiveRecursive() for each successful 'take' request. For example,
* if a task successfully 'takes' the same mutex 5 times then the mutex will
* not be available to any other task until it has also 'given' the mutex back
* exactly five times.
*
* This type of semaphore uses a priority inheritance mechanism so a task
* 'taking' a semaphore MUST ALWAYS 'give' the semaphore back once the
* semaphore it is no longer required.
*
* Mutex type semaphores cannot be used from within interrupt service routines.
*
* See xSemaphoreCreateBinary() for an alternative implementation that can be
* used for pure synchronisation (where one task or interrupt always 'gives' the
* semaphore and another always 'takes' the semaphore) and from within interrupt
* service routines.
*
* @return xSemaphore Handle to the created mutex semaphore. Should be of type
* SemaphoreHandle_t.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore;
void vATask( void * pvParameters )
{
// Semaphore cannot be used before a call to xSemaphoreCreateMutex().
// This is a macro so pass the variable in directly.
xSemaphore = xSemaphoreCreateRecursiveMutex();
if( xSemaphore != NULL )
{
// The semaphore was created successfully.
// The semaphore can now be used.
}
}
</pre>
* \defgroup xSemaphoreCreateRecursiveMutex xSemaphoreCreateRecursiveMutex
* \ingroup Semaphores
*/
#if( ( configSUPPORT_DYNAMIC_ALLOCATION == 1 ) && ( configUSE_RECURSIVE_MUTEXES == 1 ) )
#define xSemaphoreCreateRecursiveMutex() xQueueCreateMutex( queueQUEUE_TYPE_RECURSIVE_MUTEX )
#endif
/**
* semphr. h
* <pre>SemaphoreHandle_t xSemaphoreCreateRecursiveMutexStatic( StaticSemaphore_t *pxMutexBuffer )</pre>
*
* Creates a new recursive mutex type semaphore instance, and returns a handle
* by which the new recursive mutex can be referenced.
*
* Internally, within the FreeRTOS implementation, recursive mutexs use a block
* of memory, in which the mutex structure is stored. If a recursive mutex is
* created using xSemaphoreCreateRecursiveMutex() then the required memory is
* automatically dynamically allocated inside the
* xSemaphoreCreateRecursiveMutex() function. (see
* http://www.freertos.org/a00111.html). If a recursive mutex is created using
* xSemaphoreCreateRecursiveMutexStatic() then the application writer must
* provide the memory that will get used by the mutex.
* xSemaphoreCreateRecursiveMutexStatic() therefore allows a recursive mutex to
* be created without using any dynamic memory allocation.
*
* Mutexes created using this macro can be accessed using the
* xSemaphoreTakeRecursive() and xSemaphoreGiveRecursive() macros. The
* xSemaphoreTake() and xSemaphoreGive() macros must not be used.
*
* A mutex used recursively can be 'taken' repeatedly by the owner. The mutex
* doesn't become available again until the owner has called
* xSemaphoreGiveRecursive() for each successful 'take' request. For example,
* if a task successfully 'takes' the same mutex 5 times then the mutex will
* not be available to any other task until it has also 'given' the mutex back
* exactly five times.
*
* This type of semaphore uses a priority inheritance mechanism so a task
* 'taking' a semaphore MUST ALWAYS 'give' the semaphore back once the
* semaphore it is no longer required.
*
* Mutex type semaphores cannot be used from within interrupt service routines.
*
* See xSemaphoreCreateBinary() for an alternative implementation that can be
* used for pure synchronisation (where one task or interrupt always 'gives' the
* semaphore and another always 'takes' the semaphore) and from within interrupt
* service routines.
*
* @param pxMutexBuffer Must point to a variable of type StaticSemaphore_t,
* which will then be used to hold the recursive mutex's data structure,
* removing the need for the memory to be allocated dynamically.
*
* @return If the recursive mutex was successfully created then a handle to the
* created recursive mutex is returned. If pxMutexBuffer was NULL then NULL is
* returned.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore;
StaticSemaphore_t xMutexBuffer;
void vATask( void * pvParameters )
{
// A recursive semaphore cannot be used before it is created. Here a
// recursive mutex is created using xSemaphoreCreateRecursiveMutexStatic().
// The address of xMutexBuffer is passed into the function, and will hold
// the mutexes data structures - so no dynamic memory allocation will be
// attempted.
xSemaphore = xSemaphoreCreateRecursiveMutexStatic( &xMutexBuffer );
// As no dynamic memory allocation was performed, xSemaphore cannot be NULL,
// so there is no need to check it.
}
</pre>
* \defgroup xSemaphoreCreateRecursiveMutexStatic xSemaphoreCreateRecursiveMutexStatic
* \ingroup Semaphores
*/
#if( ( configSUPPORT_STATIC_ALLOCATION == 1 ) && ( configUSE_RECURSIVE_MUTEXES == 1 ) )
#define xSemaphoreCreateRecursiveMutexStatic( pxStaticSemaphore ) xQueueCreateMutexStatic( queueQUEUE_TYPE_RECURSIVE_MUTEX, pxStaticSemaphore )
#endif /* configSUPPORT_STATIC_ALLOCATION */
/**
* semphr. h
* <pre>SemaphoreHandle_t xSemaphoreCreateCounting( UBaseType_t uxMaxCount, UBaseType_t uxInitialCount )</pre>
*
* Creates a new counting semaphore instance, and returns a handle by which the
* new counting semaphore can be referenced.
*
* In many usage scenarios it is faster and more memory efficient to use a
* direct to task notification in place of a counting semaphore!
* http://www.freertos.org/RTOS-task-notifications.html
*
* Internally, within the FreeRTOS implementation, counting semaphores use a
* block of memory, in which the counting semaphore structure is stored. If a
* counting semaphore is created using xSemaphoreCreateCounting() then the
* required memory is automatically dynamically allocated inside the
* xSemaphoreCreateCounting() function. (see
* http://www.freertos.org/a00111.html). If a counting semaphore is created
* using xSemaphoreCreateCountingStatic() then the application writer can
* instead optionally provide the memory that will get used by the counting
* semaphore. xSemaphoreCreateCountingStatic() therefore allows a counting
* semaphore to be created without using any dynamic memory allocation.
*
* Counting semaphores are typically used for two things:
*
* 1) Counting events.
*
* In this usage scenario an event handler will 'give' a semaphore each time
* an event occurs (incrementing the semaphore count value), and a handler
* task will 'take' a semaphore each time it processes an event
* (decrementing the semaphore count value). The count value is therefore
* the difference between the number of events that have occurred and the
* number that have been processed. In this case it is desirable for the
* initial count value to be zero.
*
* 2) Resource management.
*
* In this usage scenario the count value indicates the number of resources
* available. To obtain control of a resource a task must first obtain a
* semaphore - decrementing the semaphore count value. When the count value
* reaches zero there are no free resources. When a task finishes with the
* resource it 'gives' the semaphore back - incrementing the semaphore count
* value. In this case it is desirable for the initial count value to be
* equal to the maximum count value, indicating that all resources are free.
*
* @param uxMaxCount The maximum count value that can be reached. When the
* semaphore reaches this value it can no longer be 'given'.
*
* @param uxInitialCount The count value assigned to the semaphore when it is
* created.
*
* @return Handle to the created semaphore. Null if the semaphore could not be
* created.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore;
void vATask( void * pvParameters )
{
SemaphoreHandle_t xSemaphore = NULL;
// Semaphore cannot be used before a call to xSemaphoreCreateCounting().
// The max value to which the semaphore can count should be 10, and the
// initial value assigned to the count should be 0.
xSemaphore = xSemaphoreCreateCounting( 10, 0 );
if( xSemaphore != NULL )
{
// The semaphore was created successfully.
// The semaphore can now be used.
}
}
</pre>
* \defgroup xSemaphoreCreateCounting xSemaphoreCreateCounting
* \ingroup Semaphores
*/
#if( configSUPPORT_DYNAMIC_ALLOCATION == 1 )
#define xSemaphoreCreateCounting( uxMaxCount, uxInitialCount ) xQueueCreateCountingSemaphore( ( uxMaxCount ), ( uxInitialCount ) )
#endif
/**
* semphr. h
* <pre>SemaphoreHandle_t xSemaphoreCreateCountingStatic( UBaseType_t uxMaxCount, UBaseType_t uxInitialCount, StaticSemaphore_t *pxSemaphoreBuffer )</pre>
*
* Creates a new counting semaphore instance, and returns a handle by which the
* new counting semaphore can be referenced.
*
* In many usage scenarios it is faster and more memory efficient to use a
* direct to task notification in place of a counting semaphore!
* http://www.freertos.org/RTOS-task-notifications.html
*
* Internally, within the FreeRTOS implementation, counting semaphores use a
* block of memory, in which the counting semaphore structure is stored. If a
* counting semaphore is created using xSemaphoreCreateCounting() then the
* required memory is automatically dynamically allocated inside the
* xSemaphoreCreateCounting() function. (see
* http://www.freertos.org/a00111.html). If a counting semaphore is created
* using xSemaphoreCreateCountingStatic() then the application writer must
* provide the memory. xSemaphoreCreateCountingStatic() therefore allows a
* counting semaphore to be created without using any dynamic memory allocation.
*
* Counting semaphores are typically used for two things:
*
* 1) Counting events.
*
* In this usage scenario an event handler will 'give' a semaphore each time
* an event occurs (incrementing the semaphore count value), and a handler
* task will 'take' a semaphore each time it processes an event
* (decrementing the semaphore count value). The count value is therefore
* the difference between the number of events that have occurred and the
* number that have been processed. In this case it is desirable for the
* initial count value to be zero.
*
* 2) Resource management.
*
* In this usage scenario the count value indicates the number of resources
* available. To obtain control of a resource a task must first obtain a
* semaphore - decrementing the semaphore count value. When the count value
* reaches zero there are no free resources. When a task finishes with the
* resource it 'gives' the semaphore back - incrementing the semaphore count
* value. In this case it is desirable for the initial count value to be
* equal to the maximum count value, indicating that all resources are free.
*
* @param uxMaxCount The maximum count value that can be reached. When the
* semaphore reaches this value it can no longer be 'given'.
*
* @param uxInitialCount The count value assigned to the semaphore when it is
* created.
*
* @param pxSemaphoreBuffer Must point to a variable of type StaticSemaphore_t,
* which will then be used to hold the semaphore's data structure, removing the
* need for the memory to be allocated dynamically.
*
* @return If the counting semaphore was successfully created then a handle to
* the created counting semaphore is returned. If pxSemaphoreBuffer was NULL
* then NULL is returned.
*
* Example usage:
<pre>
SemaphoreHandle_t xSemaphore;
StaticSemaphore_t xSemaphoreBuffer;
void vATask( void * pvParameters )
{
SemaphoreHandle_t xSemaphore = NULL;
// Counting semaphore cannot be used before they have been created. Create
// a counting semaphore using xSemaphoreCreateCountingStatic(). The max
// value to which the semaphore can count is 10, and the initial value
// assigned to the count will be 0. The address of xSemaphoreBuffer is
// passed in and will be used to hold the semaphore structure, so no dynamic
// memory allocation will be used.
xSemaphore = xSemaphoreCreateCounting( 10, 0, &xSemaphoreBuffer );
// No memory allocation was attempted so xSemaphore cannot be NULL, so there
// is no need to check its value.
}
</pre>
* \defgroup xSemaphoreCreateCountingStatic xSemaphoreCreateCountingStatic
* \ingroup Semaphores
*/
#if( configSUPPORT_STATIC_ALLOCATION == 1 )
#define xSemaphoreCreateCountingStatic( uxMaxCount, uxInitialCount, pxSemaphoreBuffer ) xQueueCreateCountingSemaphoreStatic( ( uxMaxCount ), ( uxInitialCount ), ( pxSemaphoreBuffer ) )
#endif /* configSUPPORT_STATIC_ALLOCATION */
/**
* semphr. h
* <pre>void vSemaphoreDelete( SemaphoreHandle_t xSemaphore );</pre>
*
* Delete a semaphore. This function must be used with care. For example,
* do not delete a mutex type semaphore if the mutex is held by a task.
*
* @param xSemaphore A handle to the semaphore to be deleted.
*
* \defgroup vSemaphoreDelete vSemaphoreDelete
* \ingroup Semaphores
*/
#define vSemaphoreDelete( xSemaphore ) vQueueDelete( ( QueueHandle_t ) ( xSemaphore ) )
/**
* semphr.h
* <pre>TaskHandle_t xSemaphoreGetMutexHolder( SemaphoreHandle_t xMutex );</pre>
*
* If xMutex is indeed a mutex type semaphore, return the current mutex holder.
* If xMutex is not a mutex type semaphore, or the mutex is available (not held
* by a task), return NULL.
*
* Note: This is a good way of determining if the calling task is the mutex
* holder, but not a good way of determining the identity of the mutex holder as
* the holder may change between the function exiting and the returned value
* being tested.
*/
#define xSemaphoreGetMutexHolder( xSemaphore ) xQueueGetMutexHolder( ( xSemaphore ) )
/**
* semphr.h
* <pre>TaskHandle_t xSemaphoreGetMutexHolderFromISR( SemaphoreHandle_t xMutex );</pre>
*
* If xMutex is indeed a mutex type semaphore, return the current mutex holder.
* If xMutex is not a mutex type semaphore, or the mutex is available (not held
* by a task), return NULL.
*
*/
#define xSemaphoreGetMutexHolderFromISR( xSemaphore ) xQueueGetMutexHolderFromISR( ( xSemaphore ) )
/**
* semphr.h
* <pre>UBaseType_t uxSemaphoreGetCount( SemaphoreHandle_t xSemaphore );</pre>
*
* If the semaphore is a counting semaphore then uxSemaphoreGetCount() returns
* its current count value. If the semaphore is a binary semaphore then
* uxSemaphoreGetCount() returns 1 if the semaphore is available, and 0 if the
* semaphore is not available.
*
*/
#define uxSemaphoreGetCount( xSemaphore ) uxQueueMessagesWaiting( ( QueueHandle_t ) ( xSemaphore ) )
#endif /* SEMAPHORE_H */
Details ![]()
Show: from Types: Columns: ![]( "Show Project Names")
![]( "Show Locations")
![]( "Show Referring Symbols")
![]( "Show Scope")
This file uses the notable symbols shown below. Click anywhere in the file to view more details.