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mbed-os/platform/mbed_critical.h

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/** \addtogroup platform */
/** @{*/
/*
* 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
/** 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);
/** 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);
/**
* 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 still 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
* }
*/
bool core_util_atomic_cas_u8(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 still 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
* }
*/
bool core_util_atomic_cas_u16(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 still 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
* }
*/
bool core_util_atomic_cas_u32(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 still 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
* }
*/
bool core_util_atomic_cas_ptr(void **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(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(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(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 **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(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(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(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 **valuePtr, ptrdiff_t delta);
#ifdef __cplusplus
} // extern "C"
#endif
#endif // __MBED_UTIL_CRITICAL_H__
/** @}*/
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