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Diff: mbed-os/platform/mbed_critical.h
- Revision:
- 0:8fdf9a60065b
diff -r 000000000000 -r 8fdf9a60065b mbed-os/platform/mbed_critical.h --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/mbed-os/platform/mbed_critical.h Wed Oct 10 00:33:53 2018 +0000 @@ -0,0 +1,400 @@ + +/* + * Copyright (c) 2015-2016, ARM Limited, All Rights Reserved + * SPDX-License-Identifier: Apache-2.0 + * + * Licensed under the Apache License, Version 2.0 (the "License"); you may + * not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT + * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +#ifndef __MBED_UTIL_CRITICAL_H__ +#define __MBED_UTIL_CRITICAL_H__ + +#include <stdbool.h> +#include <stdint.h> +#include <stddef.h> + +#ifdef __cplusplus +extern "C" { +#endif + +/** \addtogroup platform */ +/** @{*/ +/** + * \defgroup platform_critical critical section function + * @{ + */ + +/** Determine the current interrupts enabled state + * + * This function can be called to determine whether or not interrupts are currently enabled. + * @note + * NOTE: + * This function works for both cortex-A and cortex-M, although the underlyng implementation + * differs. + * @return true if interrupts are enabled, false otherwise + */ +bool core_util_are_interrupts_enabled(void); + +/** Determine if this code is executing from an interrupt + * + * This function can be called to determine if the code is running on interrupt context. + * @note + * NOTE: + * This function works for both cortex-A and cortex-M, although the underlyng implementation + * differs. + * @return true if in an isr, false otherwise + */ +bool core_util_is_isr_active(void); + +/** Mark the start of a critical section + * + * This function should be called to mark the start of a critical section of code. + * @note + * NOTES: + * 1) The use of this style of critical section is targetted at C based implementations. + * 2) These critical sections can be nested. + * 3) The interrupt enable state on entry to the first critical section (of a nested set, or single + * section) will be preserved on exit from the section. + * 4) This implementation will currently only work on code running in privileged mode. + */ +void core_util_critical_section_enter(void); + +/** Mark the end of a critical section + * + * This function should be called to mark the end of a critical section of code. + * @note + * NOTES: + * 1) The use of this style of critical section is targetted at C based implementations. + * 2) These critical sections can be nested. + * 3) The interrupt enable state on entry to the first critical section (of a nested set, or single + * section) will be preserved on exit from the section. + * 4) This implementation will currently only work on code running in privileged mode. + */ +void core_util_critical_section_exit(void); + +/** + * Determine if we are currently in a critical section + * + * @return true if in a critical section, false otherwise. + */ +bool core_util_in_critical_section(void); + +/** + * Atomic compare and set. It compares the contents of a memory location to a + * given value and, only if they are the same, modifies the contents of that + * memory location to a given new value. This is done as a single atomic + * operation. The atomicity guarantees that the new value is calculated based on + * up-to-date information; if the value had been updated by another thread in + * the meantime, the write would fail due to a mismatched expectedCurrentValue. + * + * Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect + * you to the article on compare-and swap]. + * + * @param ptr The target memory location. + * @param[in,out] expectedCurrentValue A pointer to some location holding the + * expected current value of the data being set atomically. + * The computed 'desiredValue' should be a function of this current value. + * @note: This is an in-out parameter. In the + * failure case of atomic_cas (where the + * destination isn't set), the pointee of expectedCurrentValue is + * updated with the current value. + * @param[in] desiredValue The new value computed based on '*expectedCurrentValue'. + * + * @return true if the memory location was atomically + * updated with the desired value (after verifying + * that it contained the expectedCurrentValue), + * false otherwise. In the failure case, + * exepctedCurrentValue is updated with the new + * value of the target memory location. + * + * pseudocode: + * function cas(p : pointer to int, old : pointer to int, new : int) returns bool { + * if *p != *old { + * *old = *p + * return false + * } + * *p = new + * return true + * } + * + * @note: In the failure case (where the destination isn't set), the value + * pointed to by expectedCurrentValue is instead updated with the current value. + * This property helps writing concise code for the following incr: + * + * function incr(p : pointer to int, a : int) returns int { + * done = false + * value = *p // This fetch operation need not be atomic. + * while not done { + * done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success + * } + * return value + a + * } + * + * @note: This corresponds to the C11 "atomic_compare_exchange_strong" - it + * always succeeds if the current value is expected, as per the pseudocode + * above; it will not spuriously fail as "atomic_compare_exchange_weak" may. + */ +bool core_util_atomic_cas_u8(volatile uint8_t *ptr, uint8_t *expectedCurrentValue, uint8_t desiredValue); + +/** + * Atomic compare and set. It compares the contents of a memory location to a + * given value and, only if they are the same, modifies the contents of that + * memory location to a given new value. This is done as a single atomic + * operation. The atomicity guarantees that the new value is calculated based on + * up-to-date information; if the value had been updated by another thread in + * the meantime, the write would fail due to a mismatched expectedCurrentValue. + * + * Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect + * you to the article on compare-and swap]. + * + * @param ptr The target memory location. + * @param[in,out] expectedCurrentValue A pointer to some location holding the + * expected current value of the data being set atomically. + * The computed 'desiredValue' should be a function of this current value. + * @note: This is an in-out parameter. In the + * failure case of atomic_cas (where the + * destination isn't set), the pointee of expectedCurrentValue is + * updated with the current value. + * @param[in] desiredValue The new value computed based on '*expectedCurrentValue'. + * + * @return true if the memory location was atomically + * updated with the desired value (after verifying + * that it contained the expectedCurrentValue), + * false otherwise. In the failure case, + * exepctedCurrentValue is updated with the new + * value of the target memory location. + * + * pseudocode: + * function cas(p : pointer to int, old : pointer to int, new : int) returns bool { + * if *p != *old { + * *old = *p + * return false + * } + * *p = new + * return true + * } + * + * @note: In the failure case (where the destination isn't set), the value + * pointed to by expectedCurrentValue is instead updated with the current value. + * This property helps writing concise code for the following incr: + * + * function incr(p : pointer to int, a : int) returns int { + * done = false + * value = *p // This fetch operation need not be atomic. + * while not done { + * done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success + * } + * return value + a + * } + * + * @note: This corresponds to the C11 "atomic_compare_exchange_strong" - it + * always succeeds if the current value is expected, as per the pseudocode + * above; it will not spuriously fail as "atomic_compare_exchange_weak" may. + */ +bool core_util_atomic_cas_u16(volatile uint16_t *ptr, uint16_t *expectedCurrentValue, uint16_t desiredValue); + +/** + * Atomic compare and set. It compares the contents of a memory location to a + * given value and, only if they are the same, modifies the contents of that + * memory location to a given new value. This is done as a single atomic + * operation. The atomicity guarantees that the new value is calculated based on + * up-to-date information; if the value had been updated by another thread in + * the meantime, the write would fail due to a mismatched expectedCurrentValue. + * + * Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect + * you to the article on compare-and swap]. + * + * @param ptr The target memory location. + * @param[in,out] expectedCurrentValue A pointer to some location holding the + * expected current value of the data being set atomically. + * The computed 'desiredValue' should be a function of this current value. + * @note: This is an in-out parameter. In the + * failure case of atomic_cas (where the + * destination isn't set), the pointee of expectedCurrentValue is + * updated with the current value. + * @param[in] desiredValue The new value computed based on '*expectedCurrentValue'. + * + * @return true if the memory location was atomically + * updated with the desired value (after verifying + * that it contained the expectedCurrentValue), + * false otherwise. In the failure case, + * exepctedCurrentValue is updated with the new + * value of the target memory location. + * + * pseudocode: + * function cas(p : pointer to int, old : pointer to int, new : int) returns bool { + * if *p != *old { + * *old = *p + * return false + * } + * *p = new + * return true + * } + * + * @note: In the failure case (where the destination isn't set), the value + * pointed to by expectedCurrentValue is instead updated with the current value. + * This property helps writing concise code for the following incr: + * + * function incr(p : pointer to int, a : int) returns int { + * done = false + * value = *p // This fetch operation need not be atomic. + * while not done { + * done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success + * } + * return value + a + * + * @note: This corresponds to the C11 "atomic_compare_exchange_strong" - it + * always succeeds if the current value is expected, as per the pseudocode + * above; it will not spuriously fail as "atomic_compare_exchange_weak" may. + * } + */ +bool core_util_atomic_cas_u32(volatile uint32_t *ptr, uint32_t *expectedCurrentValue, uint32_t desiredValue); + +/** + * Atomic compare and set. It compares the contents of a memory location to a + * given value and, only if they are the same, modifies the contents of that + * memory location to a given new value. This is done as a single atomic + * operation. The atomicity guarantees that the new value is calculated based on + * up-to-date information; if the value had been updated by another thread in + * the meantime, the write would fail due to a mismatched expectedCurrentValue. + * + * Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect + * you to the article on compare-and swap]. + * + * @param ptr The target memory location. + * @param[in,out] expectedCurrentValue A pointer to some location holding the + * expected current value of the data being set atomically. + * The computed 'desiredValue' should be a function of this current value. + * @note: This is an in-out parameter. In the + * failure case of atomic_cas (where the + * destination isn't set), the pointee of expectedCurrentValue is + * updated with the current value. + * @param[in] desiredValue The new value computed based on '*expectedCurrentValue'. + * + * @return true if the memory location was atomically + * updated with the desired value (after verifying + * that it contained the expectedCurrentValue), + * false otherwise. In the failure case, + * exepctedCurrentValue is updated with the new + * value of the target memory location. + * + * pseudocode: + * function cas(p : pointer to int, old : pointer to int, new : int) returns bool { + * if *p != *old { + * *old = *p + * return false + * } + * *p = new + * return true + * } + * + * @note: In the failure case (where the destination isn't set), the value + * pointed to by expectedCurrentValue is instead updated with the current value. + * This property helps writing concise code for the following incr: + * + * function incr(p : pointer to int, a : int) returns int { + * done = false + * value = *p // This fetch operation need not be atomic. + * while not done { + * done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success + * } + * return value + a + * } + * + * @note: This corresponds to the C11 "atomic_compare_exchange_strong" - it + * always succeeds if the current value is expected, as per the pseudocode + * above; it will not spuriously fail as "atomic_compare_exchange_weak" may. + */ +bool core_util_atomic_cas_ptr(void *volatile *ptr, void **expectedCurrentValue, void *desiredValue); + +/** + * Atomic increment. + * @param valuePtr Target memory location being incremented. + * @param delta The amount being incremented. + * @return The new incremented value. + */ +uint8_t core_util_atomic_incr_u8(volatile uint8_t *valuePtr, uint8_t delta); + +/** + * Atomic increment. + * @param valuePtr Target memory location being incremented. + * @param delta The amount being incremented. + * @return The new incremented value. + */ +uint16_t core_util_atomic_incr_u16(volatile uint16_t *valuePtr, uint16_t delta); + +/** + * Atomic increment. + * @param valuePtr Target memory location being incremented. + * @param delta The amount being incremented. + * @return The new incremented value. + */ +uint32_t core_util_atomic_incr_u32(volatile uint32_t *valuePtr, uint32_t delta); + +/** + * Atomic increment. + * @param valuePtr Target memory location being incremented. + * @param delta The amount being incremented in bytes. + * @return The new incremented value. + * + * @note The type of the pointer argument is not taken into account + * and the pointer is incremented by bytes. + */ +void *core_util_atomic_incr_ptr(void *volatile *valuePtr, ptrdiff_t delta); + +/** + * Atomic decrement. + * @param valuePtr Target memory location being decremented. + * @param delta The amount being decremented. + * @return The new decremented value. + */ +uint8_t core_util_atomic_decr_u8(volatile uint8_t *valuePtr, uint8_t delta); + +/** + * Atomic decrement. + * @param valuePtr Target memory location being decremented. + * @param delta The amount being decremented. + * @return The new decremented value. + */ +uint16_t core_util_atomic_decr_u16(volatile uint16_t *valuePtr, uint16_t delta); + +/** + * Atomic decrement. + * @param valuePtr Target memory location being decremented. + * @param delta The amount being decremented. + * @return The new decremented value. + */ +uint32_t core_util_atomic_decr_u32(volatile uint32_t *valuePtr, uint32_t delta); + +/** + * Atomic decrement. + * @param valuePtr Target memory location being decremented. + * @param delta The amount being decremented in bytes. + * @return The new decremented value. + * + * @note The type of the pointer argument is not taken into account + * and the pointer is decremented by bytes + */ +void *core_util_atomic_decr_ptr(void *volatile *valuePtr, ptrdiff_t delta); + +#ifdef __cplusplus +} // extern "C" +#endif +/**@}*/ + +/**@}*/ + +#endif // __MBED_UTIL_CRITICAL_H__ + + +