critical_section_api.h

00001 /** \addtogroup hal */
00002 /** @{*/
00003 /* mbed Microcontroller Library
00004  * Copyright (c) 2006-2017 ARM Limited
00005  *
00006  * Licensed under the Apache License, Version 2.0 (the "License");
00007  * you may not use this file except in compliance with the License.
00008  * You may obtain a copy of the License at
00009  *
00010  *     http://www.apache.org/licenses/LICENSE-2.0
00011  *
00012  * Unless required by applicable law or agreed to in writing, software
00013  * distributed under the License is distributed on an "AS IS" BASIS,
00014  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00015  * See the License for the specific language governing permissions and
00016  * limitations under the License.
00017  */
00018 #ifndef MBED_CRITICAL_SECTION_API_H
00019 #define MBED_CRITICAL_SECTION_API_H
00020 
00021 #include <stdbool.h>
00022 
00023 #ifdef __cplusplus
00024 extern "C" {
00025 #endif
00026 
00027 /**
00028  * \defgroup hal_critical Critical Section HAL functions
00029  * @{
00030  */
00031 
00032 /**
00033  * Mark the start of a critical section
00034  *
00035  * This function will be called by core_util_critical_section_enter() each time
00036  * the application requests to enter a critical section. The purpose of the
00037  * critical section is to ensure mutual-exclusion synchronisation of the
00038  * processor by preventing any change in processor control, the default
00039  * behaviour requires storing the state of interrupts in the system before
00040  * disabling them.
00041  *
00042  * The critical section code supports nesting. When a thread has entered a
00043  * critical section it can make additional calls to
00044  * core_util_critical_section_enter() without deadlocking itself. The critical
00045  * section driver API tracks the number of nested calls to the critical section.
00046  * The critical section will only be exited when
00047  * core_util_critical_section_exit() has been called once for each time it
00048  * entered the critical section.
00049  *
00050  * On the first call to enter a critical section this function MUST store the
00051  * state of any interrupts or other application settings it will modify to
00052  * facilitate the critical section.
00053  *
00054  * Each successive call to enter the critical section MUST ignore storing or
00055  * modifying any application state.
00056  *
00057  * The default implementation of this function which will save the current state
00058  * of interrupts before disabling them. This implementation can be found in
00059  * mbed_critical_section_api.c. This behaviour is can be overridden on a per
00060  * platform basis by providing a different implementation within the correct
00061  * targets directory.
00062  */
00063 void hal_critical_section_enter(void);
00064 
00065 
00066 /** Mark the end of a critical section.
00067  *
00068  * The purpose of this function is to restore any state that was modified upon
00069  * entering the critical section, allowing other threads or interrupts to change
00070  * the processor control.
00071  *
00072  * This function will be called once by core_util_critical_section_exit() per
00073  * critical section on last call to exit. When called, the application MUST
00074  * restore the saved interrupt/application state that was saved when entering
00075  * the critical section.
00076  *
00077  * There is a default implementation of this function, it will restore the state
00078  * of interrupts that were previously saved when hal_critical_section_enter was
00079  * first called, this implementation can be found in
00080  * mbed_critical_section_api.c. This behaviour is overridable by providing a
00081  * different function implementation within the correct targets directory.
00082  */
00083 void hal_critical_section_exit(void);
00084 
00085 
00086 /** Determine if the application is currently running in a critical section
00087  *
00088  * The purpose of this function is to inform the caller whether or not the
00089  * application is running in a critical section. This is done by checking if
00090  * the current interrupt state has been saved in the underlying implementation,
00091  * this could also be done by checking the state of the interrupts at the time
00092  * of calling.
00093  *
00094  *  @return  True if running in a critical section, false if not.
00095  */
00096 bool hal_in_critical_section(void);
00097 
00098 
00099 /**@}*/
00100 
00101 #ifdef __cplusplus
00102 }
00103 #endif
00104 
00105 #endif // MBED_CRITICAL_SECTION_API_H
00106 
00107 /** @}*/