mbed_critical_section_api.c

00001 /* mbed Microcontroller Library
00002  * Copyright (c) 2017 ARM Limited
00003  *
00004  * Licensed under the Apache License, Version 2.0 (the "License");
00005  * you may not use this file except in compliance with the License.
00006  * You may obtain a copy of the License at
00007  *
00008  *     http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 #include "cmsis.h"
00017 #include "hal/critical_section_api.h"
00018 #include "platform/mbed_assert.h"
00019 #include "platform/mbed_toolchain.h"
00020 
00021 #include <stdbool.h>
00022 
00023 static volatile bool critical_interrupts_enabled = false;
00024 static volatile bool state_saved = false;
00025 
00026 static bool are_interrupts_enabled(void)
00027 {
00028 #if defined(__CORTEX_A9)
00029     return ((__get_CPSR() & 0x80) == 0);
00030 #else
00031     return ((__get_PRIMASK() & 0x1) == 0);
00032 #endif
00033 }
00034 
00035 
00036 MBED_WEAK void hal_critical_section_enter(void)
00037 {
00038     const bool interrupt_state = are_interrupts_enabled();
00039 
00040     __disable_irq();
00041 
00042     if (state_saved == true) {
00043         return;
00044     }
00045 
00046     critical_interrupts_enabled = interrupt_state;
00047     state_saved = true;
00048 }
00049 
00050 MBED_WEAK void hal_critical_section_exit(void)
00051 {
00052 #ifndef FEATURE_UVISOR
00053     // Interrupts must be disabled on invoking an exit from a critical section
00054     MBED_ASSERT(!are_interrupts_enabled());
00055 #endif
00056     state_saved = false;
00057 
00058     // Restore the IRQs to their state prior to entering the critical section
00059     if (critical_interrupts_enabled == true) {
00060         __enable_irq();
00061     }
00062 }
00063 
00064 MBED_WEAK bool hal_in_critical_section(void)
00065 {
00066     return (state_saved == true);
00067 }