critical_section_api.h

00001 /** \addtogroup hal */
00002 /** @{*/
00003 /* mbed Microcontroller Library
00004  * Copyright (c) 2006-2017 ARM Limited
00005  * SPDX-License-Identifier: Apache-2.0
00006  *
00007  * Licensed under the Apache License, Version 2.0 (the "License");
00008  * you may not use this file except in compliance with the License.
00009  * You may obtain a copy of the License at
00010  *
00011  *     http://www.apache.org/licenses/LICENSE-2.0
00012  *
00013  * Unless required by applicable law or agreed to in writing, software
00014  * distributed under the License is distributed on an "AS IS" BASIS,
00015  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00016  * See the License for the specific language governing permissions and
00017  * limitations under the License.
00018  */
00019 #ifndef MBED_CRITICAL_SECTION_API_H
00020 #define MBED_CRITICAL_SECTION_API_H
00021 
00022 #include <stdbool.h>
00023 
00024 #ifdef __cplusplus
00025 extern "C" {
00026 #endif
00027 
00028 /**
00029  * \defgroup hal_critical Critical Section HAL functions
00030  * @{
00031  */
00032 
00033 /**
00034  * Mark the start of a critical section
00035  *
00036  * This function will be called by core_util_critical_section_enter() each time
00037  * the application requests to enter a critical section. The purpose of the
00038  * critical section is to ensure mutual-exclusion synchronisation of the
00039  * processor by preventing any change in processor control, the default
00040  * behaviour requires storing the state of interrupts in the system before
00041  * disabling them.
00042  *
00043  * The critical section code supports nesting. When a thread has entered a
00044  * critical section it can make additional calls to
00045  * core_util_critical_section_enter() without deadlocking itself. The critical
00046  * section driver API tracks the number of nested calls to the critical section.
00047  * The critical section will only be exited when
00048  * core_util_critical_section_exit() has been called once for each time it
00049  * entered the critical section.
00050  *
00051  * On the first call to enter a critical section this function MUST store the
00052  * state of any interrupts or other application settings it will modify to
00053  * facilitate the critical section.
00054  *
00055  * Each successive call to enter the critical section MUST ignore storing or
00056  * modifying any application state.
00057  *
00058  * The default implementation of this function which will save the current state
00059  * of interrupts before disabling them. This implementation can be found in
00060  * mbed_critical_section_api.c. This behaviour is can be overridden on a per
00061  * platform basis by providing a different implementation within the correct
00062  * targets directory.
00063  */
00064 void hal_critical_section_enter(void);
00065 
00066 
00067 /** Mark the end of a critical section.
00068  *
00069  * The purpose of this function is to restore any state that was modified upon
00070  * entering the critical section, allowing other threads or interrupts to change
00071  * the processor control.
00072  *
00073  * This function will be called once by core_util_critical_section_exit() per
00074  * critical section on last call to exit. When called, the application MUST
00075  * restore the saved interrupt/application state that was saved when entering
00076  * the critical section.
00077  *
00078  * There is a default implementation of this function, it will restore the state
00079  * of interrupts that were previously saved when hal_critical_section_enter was
00080  * first called, this implementation can be found in
00081  * mbed_critical_section_api.c. This behaviour is overridable by providing a
00082  * different function implementation within the correct targets directory.
00083  */
00084 void hal_critical_section_exit(void);
00085 
00086 
00087 /** Determine if the application is currently running in a critical section
00088  *
00089  * The purpose of this function is to inform the caller whether or not the
00090  * application is running in a critical section. This is done by checking if
00091  * the current interrupt state has been saved in the underlying implementation,
00092  * this could also be done by checking the state of the interrupts at the time
00093  * of calling.
00094  *
00095  *  @return  True if running in a critical section, false if not.
00096  */
00097 bool hal_in_critical_section(void);
00098 
00099 
00100 /**@}*/
00101 
00102 #ifdef __cplusplus
00103 }
00104 #endif
00105 
00106 #endif // MBED_CRITICAL_SECTION_API_H
00107 
00108 /** @}*/