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critical_section_api.h
1 /** \addtogroup hal */
2 /** @{*/
3 /* mbed Microcontroller Library
4  * Copyright (c) 2006-2017 ARM Limited
5  * SPDX-License-Identifier: Apache-2.0
6  *
7  * Licensed under the Apache License, Version 2.0 (the "License");
8  * you may not use this file except in compliance with the License.
9  * You may obtain a copy of the License at
10  *
11  * http://www.apache.org/licenses/LICENSE-2.0
12  *
13  * Unless required by applicable law or agreed to in writing, software
14  * distributed under the License is distributed on an "AS IS" BASIS,
15  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16  * See the License for the specific language governing permissions and
17  * limitations under the License.
18  */
19 #ifndef MBED_CRITICAL_SECTION_API_H
20 #define MBED_CRITICAL_SECTION_API_H
21 
22 #include <stdbool.h>
23 
24 #ifdef __cplusplus
25 extern "C" {
26 #endif
27 
28 /**
29  * \defgroup hal_critical Critical Section HAL functions
30  * @{
31  */
32 
33 /**
34  * Mark the start of a critical section
35  *
36  * This function will be called by core_util_critical_section_enter() each time
37  * the application requests to enter a critical section. The purpose of the
38  * critical section is to ensure mutual-exclusion synchronisation of the
39  * processor by preventing any change in processor control, the default
40  * behaviour requires storing the state of interrupts in the system before
41  * disabling them.
42  *
43  * The critical section code supports nesting. When a thread has entered a
44  * critical section it can make additional calls to
45  * core_util_critical_section_enter() without deadlocking itself. The critical
46  * section driver API tracks the number of nested calls to the critical section.
47  * The critical section will only be exited when
48  * core_util_critical_section_exit() has been called once for each time it
49  * entered the critical section.
50  *
51  * On the first call to enter a critical section this function MUST store the
52  * state of any interrupts or other application settings it will modify to
53  * facilitate the critical section.
54  *
55  * Each successive call to enter the critical section MUST ignore storing or
56  * modifying any application state.
57  *
58  * The default implementation of this function which will save the current state
59  * of interrupts before disabling them. This implementation can be found in
60  * mbed_critical_section_api.c. This behaviour is can be overridden on a per
61  * platform basis by providing a different implementation within the correct
62  * targets directory.
63  */
64 void hal_critical_section_enter(void);
65 
66 
67 /** Mark the end of a critical section.
68  *
69  * The purpose of this function is to restore any state that was modified upon
70  * entering the critical section, allowing other threads or interrupts to change
71  * the processor control.
72  *
73  * This function will be called once by core_util_critical_section_exit() per
74  * critical section on last call to exit. When called, the application MUST
75  * restore the saved interrupt/application state that was saved when entering
76  * the critical section.
77  *
78  * There is a default implementation of this function, it will restore the state
79  * of interrupts that were previously saved when hal_critical_section_enter was
80  * first called, this implementation can be found in
81  * mbed_critical_section_api.c. This behaviour is overridable by providing a
82  * different function implementation within the correct targets directory.
83  */
84 void hal_critical_section_exit(void);
85 
86 
87 /** Determine if the application is currently running in a critical section
88  *
89  * The purpose of this function is to inform the caller whether or not the
90  * application is running in a critical section. This is done by checking if
91  * the current interrupt state has been saved in the underlying implementation,
92  * this could also be done by checking the state of the interrupts at the time
93  * of calling.
94  *
95  * @return True if running in a critical section, false if not.
96  */
97 bool hal_in_critical_section(void);
98 
99 
100 /**@}*/
101 
102 #ifdef __cplusplus
103 }
104 #endif
105 
106 #endif // MBED_CRITICAL_SECTION_API_H
107 
108 /** @}*/
hal_critical_section_enter
void hal_critical_section_enter(void)
Mark the start of a critical section.
hal_critical_section_exit
void hal_critical_section_exit(void)
Mark the end of a critical section.
hal_in_critical_section
bool hal_in_critical_section(void)
Determine if the application is currently running in a critical section.
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