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platform/mbed_critical.h@172:65be27845400, 2019-02-20 (annotated)

Committer:
AnnaBridge
Date:
Wed Feb 20 20:53:29 2019 +0000
Revision:
172:65be27845400
Parent:
171:3a7713b1edbc 
mbed library release version 165

Who changed what in which revision?

UserRevisionLine numberNew contents of line
AnnaBridge 156:ff21514d8981 1
AnnaBridge 156:ff21514d8981 2 /*
AnnaBridge 156:ff21514d8981 3 * Copyright (c) 2015-2016, ARM Limited, All Rights Reserved
AnnaBridge 156:ff21514d8981 4 * SPDX-License-Identifier: Apache-2.0
AnnaBridge 156:ff21514d8981 5 *
AnnaBridge 156:ff21514d8981 6 * Licensed under the Apache License, Version 2.0 (the "License"); you may
AnnaBridge 156:ff21514d8981 7 * not use this file except in compliance with the License.
AnnaBridge 156:ff21514d8981 8 * You may obtain a copy of the License at
AnnaBridge 156:ff21514d8981 9 *
AnnaBridge 156:ff21514d8981 10 * http://www.apache.org/licenses/LICENSE-2.0
AnnaBridge 156:ff21514d8981 11 *
AnnaBridge 156:ff21514d8981 12 * Unless required by applicable law or agreed to in writing, software
AnnaBridge 156:ff21514d8981 13 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
AnnaBridge 156:ff21514d8981 14 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
AnnaBridge 156:ff21514d8981 15 * See the License for the specific language governing permissions and
AnnaBridge 156:ff21514d8981 16 * limitations under the License.
AnnaBridge 156:ff21514d8981 17 */
AnnaBridge 156:ff21514d8981 18
AnnaBridge 156:ff21514d8981 19 #ifndef __MBED_UTIL_CRITICAL_H__
AnnaBridge 156:ff21514d8981 20 #define __MBED_UTIL_CRITICAL_H__
AnnaBridge 156:ff21514d8981 21
AnnaBridge 156:ff21514d8981 22 #include <stdbool.h>
AnnaBridge 156:ff21514d8981 23 #include <stdint.h>
AnnaBridge 156:ff21514d8981 24 #include <stddef.h>
AnnaBridge 156:ff21514d8981 25
AnnaBridge 156:ff21514d8981 26 #ifdef __cplusplus
AnnaBridge 156:ff21514d8981 27 extern "C" {
AnnaBridge 156:ff21514d8981 28 #endif
AnnaBridge 156:ff21514d8981 29
AnnaBridge 158:1c57384330a6 30 /** \addtogroup platform */
AnnaBridge 158:1c57384330a6 31 /** @{*/
AnnaBridge 158:1c57384330a6 32 /**
AnnaBridge 158:1c57384330a6 33 * \defgroup platform_critical critical section function
AnnaBridge 158:1c57384330a6 34 * @{
AnnaBridge 158:1c57384330a6 35 */
AnnaBridge 156:ff21514d8981 36
AnnaBridge 156:ff21514d8981 37 /** Determine the current interrupts enabled state
AnnaBridge 156:ff21514d8981 38 *
AnnaBridge 156:ff21514d8981 39 * This function can be called to determine whether or not interrupts are currently enabled.
AnnaBridge 156:ff21514d8981 40 * @note
AnnaBridge 156:ff21514d8981 41 * NOTE:
AnnaBridge 171:3a7713b1edbc 42 * This function works for both cortex-A and cortex-M, although the underlying implementation
AnnaBridge 156:ff21514d8981 43 * differs.
AnnaBridge 156:ff21514d8981 44 * @return true if interrupts are enabled, false otherwise
AnnaBridge 156:ff21514d8981 45 */
AnnaBridge 156:ff21514d8981 46 bool core_util_are_interrupts_enabled(void);
AnnaBridge 156:ff21514d8981 47
AnnaBridge 156:ff21514d8981 48 /** Determine if this code is executing from an interrupt
AnnaBridge 156:ff21514d8981 49 *
AnnaBridge 156:ff21514d8981 50 * This function can be called to determine if the code is running on interrupt context.
AnnaBridge 156:ff21514d8981 51 * @note
AnnaBridge 156:ff21514d8981 52 * NOTE:
AnnaBridge 171:3a7713b1edbc 53 * This function works for both cortex-A and cortex-M, although the underlying implementation
AnnaBridge 156:ff21514d8981 54 * differs.
AnnaBridge 156:ff21514d8981 55 * @return true if in an isr, false otherwise
AnnaBridge 156:ff21514d8981 56 */
AnnaBridge 156:ff21514d8981 57 bool core_util_is_isr_active(void);
AnnaBridge 156:ff21514d8981 58
AnnaBridge 156:ff21514d8981 59 /** Mark the start of a critical section
AnnaBridge 156:ff21514d8981 60 *
AnnaBridge 156:ff21514d8981 61 * This function should be called to mark the start of a critical section of code.
AnnaBridge 156:ff21514d8981 62 * @note
AnnaBridge 156:ff21514d8981 63 * NOTES:
AnnaBridge 156:ff21514d8981 64 * 1) The use of this style of critical section is targetted at C based implementations.
AnnaBridge 156:ff21514d8981 65 * 2) These critical sections can be nested.
AnnaBridge 156:ff21514d8981 66 * 3) The interrupt enable state on entry to the first critical section (of a nested set, or single
AnnaBridge 156:ff21514d8981 67 * section) will be preserved on exit from the section.
AnnaBridge 156:ff21514d8981 68 * 4) This implementation will currently only work on code running in privileged mode.
AnnaBridge 156:ff21514d8981 69 */
AnnaBridge 156:ff21514d8981 70 void core_util_critical_section_enter(void);
AnnaBridge 156:ff21514d8981 71
AnnaBridge 156:ff21514d8981 72 /** Mark the end of a critical section
AnnaBridge 156:ff21514d8981 73 *
AnnaBridge 156:ff21514d8981 74 * This function should be called to mark the end of a critical section of code.
AnnaBridge 156:ff21514d8981 75 * @note
AnnaBridge 156:ff21514d8981 76 * NOTES:
AnnaBridge 156:ff21514d8981 77 * 1) The use of this style of critical section is targetted at C based implementations.
AnnaBridge 156:ff21514d8981 78 * 2) These critical sections can be nested.
AnnaBridge 156:ff21514d8981 79 * 3) The interrupt enable state on entry to the first critical section (of a nested set, or single
AnnaBridge 156:ff21514d8981 80 * section) will be preserved on exit from the section.
AnnaBridge 156:ff21514d8981 81 * 4) This implementation will currently only work on code running in privileged mode.
AnnaBridge 156:ff21514d8981 82 */
AnnaBridge 156:ff21514d8981 83 void core_util_critical_section_exit(void);
AnnaBridge 156:ff21514d8981 84
AnnaBridge 156:ff21514d8981 85 /**
AnnaBridge 165:d1b4690b3f8b 86 * Determine if we are currently in a critical section
AnnaBridge 165:d1b4690b3f8b 87 *
AnnaBridge 165:d1b4690b3f8b 88 * @return true if in a critical section, false otherwise.
AnnaBridge 165:d1b4690b3f8b 89 */
AnnaBridge 165:d1b4690b3f8b 90 bool core_util_in_critical_section(void);
AnnaBridge 165:d1b4690b3f8b 91
AnnaBridge 165:d1b4690b3f8b 92 /**
AnnaBridge 172:65be27845400 93 * A lock-free, primitive atomic flag.
AnnaBridge 172:65be27845400 94 *
AnnaBridge 172:65be27845400 95 * Emulate C11's atomic_flag. The flag is initially in an indeterminate state
AnnaBridge 172:65be27845400 96 * unless explicitly initialized with CORE_UTIL_ATOMIC_FLAG_INIT.
AnnaBridge 172:65be27845400 97 */
AnnaBridge 172:65be27845400 98 typedef struct core_util_atomic_flag {
AnnaBridge 172:65be27845400 99 uint8_t _flag;
AnnaBridge 172:65be27845400 100 } core_util_atomic_flag;
AnnaBridge 172:65be27845400 101
AnnaBridge 172:65be27845400 102 /**
AnnaBridge 172:65be27845400 103 * Initializer for a core_util_atomic_flag.
AnnaBridge 172:65be27845400 104 *
AnnaBridge 172:65be27845400 105 * Example:
AnnaBridge 172:65be27845400 106 * ~~~
AnnaBridge 172:65be27845400 107 * core_util_atomic_flag in_progress = CORE_UTIL_ATOMIC_FLAG_INIT;
AnnaBridge 172:65be27845400 108 * ~~~
AnnaBridge 172:65be27845400 109 */
AnnaBridge 172:65be27845400 110 #define CORE_UTIL_ATOMIC_FLAG_INIT { 0 }
AnnaBridge 172:65be27845400 111
AnnaBridge 172:65be27845400 112 /**
AnnaBridge 172:65be27845400 113 * Atomic test and set.
AnnaBridge 172:65be27845400 114 *
AnnaBridge 172:65be27845400 115 * Atomically tests then sets the flag to true, returning the previous value.
AnnaBridge 172:65be27845400 116 *
AnnaBridge 172:65be27845400 117 * @param flagPtr Target flag being tested and set.
AnnaBridge 172:65be27845400 118 * @return The previous value.
AnnaBridge 172:65be27845400 119 */
AnnaBridge 172:65be27845400 120 bool core_util_atomic_flag_test_and_set(volatile core_util_atomic_flag *flagPtr);
AnnaBridge 172:65be27845400 121
AnnaBridge 172:65be27845400 122 /**
AnnaBridge 172:65be27845400 123 * Atomic clear.
AnnaBridge 172:65be27845400 124 *
AnnaBridge 172:65be27845400 125 * @param flagPtr Target flag being cleared.
AnnaBridge 172:65be27845400 126 */
AnnaBridge 172:65be27845400 127 void core_util_atomic_flag_clear(volatile core_util_atomic_flag *flagPtr);
AnnaBridge 172:65be27845400 128
AnnaBridge 172:65be27845400 129 /**
AnnaBridge 156:ff21514d8981 130 * Atomic compare and set. It compares the contents of a memory location to a
AnnaBridge 156:ff21514d8981 131 * given value and, only if they are the same, modifies the contents of that
AnnaBridge 156:ff21514d8981 132 * memory location to a given new value. This is done as a single atomic
AnnaBridge 156:ff21514d8981 133 * operation. The atomicity guarantees that the new value is calculated based on
AnnaBridge 156:ff21514d8981 134 * up-to-date information; if the value had been updated by another thread in
AnnaBridge 156:ff21514d8981 135 * the meantime, the write would fail due to a mismatched expectedCurrentValue.
AnnaBridge 156:ff21514d8981 136 *
AnnaBridge 156:ff21514d8981 137 * Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect
AnnaBridge 156:ff21514d8981 138 * you to the article on compare-and swap].
AnnaBridge 156:ff21514d8981 139 *
AnnaBridge 156:ff21514d8981 140 * @param ptr The target memory location.
AnnaBridge 156:ff21514d8981 141 * @param[in,out] expectedCurrentValue A pointer to some location holding the
AnnaBridge 156:ff21514d8981 142 * expected current value of the data being set atomically.
AnnaBridge 156:ff21514d8981 143 * The computed 'desiredValue' should be a function of this current value.
AnnaBridge 156:ff21514d8981 144 * @note: This is an in-out parameter. In the
AnnaBridge 156:ff21514d8981 145 * failure case of atomic_cas (where the
AnnaBridge 156:ff21514d8981 146 * destination isn't set), the pointee of expectedCurrentValue is
AnnaBridge 156:ff21514d8981 147 * updated with the current value.
AnnaBridge 156:ff21514d8981 148 * @param[in] desiredValue The new value computed based on '*expectedCurrentValue'.
AnnaBridge 156:ff21514d8981 149 *
AnnaBridge 156:ff21514d8981 150 * @return true if the memory location was atomically
AnnaBridge 156:ff21514d8981 151 * updated with the desired value (after verifying
AnnaBridge 156:ff21514d8981 152 * that it contained the expectedCurrentValue),
AnnaBridge 156:ff21514d8981 153 * false otherwise. In the failure case,
AnnaBridge 156:ff21514d8981 154 * exepctedCurrentValue is updated with the new
AnnaBridge 156:ff21514d8981 155 * value of the target memory location.
AnnaBridge 156:ff21514d8981 156 *
AnnaBridge 156:ff21514d8981 157 * pseudocode:
AnnaBridge 156:ff21514d8981 158 * function cas(p : pointer to int, old : pointer to int, new : int) returns bool {
AnnaBridge 156:ff21514d8981 159 * if *p != *old {
AnnaBridge 156:ff21514d8981 160 * *old = *p
AnnaBridge 156:ff21514d8981 161 * return false
AnnaBridge 156:ff21514d8981 162 * }
AnnaBridge 156:ff21514d8981 163 * *p = new
AnnaBridge 156:ff21514d8981 164 * return true
AnnaBridge 156:ff21514d8981 165 * }
AnnaBridge 156:ff21514d8981 166 *
AnnaBridge 156:ff21514d8981 167 * @note: In the failure case (where the destination isn't set), the value
Anna Bridge 160:5571c4ff569f 168 * pointed to by expectedCurrentValue is instead updated with the current value.
AnnaBridge 156:ff21514d8981 169 * This property helps writing concise code for the following incr:
AnnaBridge 156:ff21514d8981 170 *
AnnaBridge 156:ff21514d8981 171 * function incr(p : pointer to int, a : int) returns int {
AnnaBridge 156:ff21514d8981 172 * done = false
AnnaBridge 156:ff21514d8981 173 * value = *p // This fetch operation need not be atomic.
AnnaBridge 156:ff21514d8981 174 * while not done {
AnnaBridge 156:ff21514d8981 175 * done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success
AnnaBridge 156:ff21514d8981 176 * }
AnnaBridge 156:ff21514d8981 177 * return value + a
AnnaBridge 156:ff21514d8981 178 * }
Anna Bridge 160:5571c4ff569f 179 *
Anna Bridge 160:5571c4ff569f 180 * @note: This corresponds to the C11 "atomic_compare_exchange_strong" - it
Anna Bridge 160:5571c4ff569f 181 * always succeeds if the current value is expected, as per the pseudocode
Anna Bridge 160:5571c4ff569f 182 * above; it will not spuriously fail as "atomic_compare_exchange_weak" may.
AnnaBridge 156:ff21514d8981 183 */
AnnaBridge 165:d1b4690b3f8b 184 bool core_util_atomic_cas_u8(volatile uint8_t *ptr, uint8_t *expectedCurrentValue, uint8_t desiredValue);
AnnaBridge 156:ff21514d8981 185
AnnaBridge 156:ff21514d8981 186 /**
AnnaBridge 156:ff21514d8981 187 * Atomic compare and set. It compares the contents of a memory location to a
AnnaBridge 156:ff21514d8981 188 * given value and, only if they are the same, modifies the contents of that
AnnaBridge 156:ff21514d8981 189 * memory location to a given new value. This is done as a single atomic
AnnaBridge 156:ff21514d8981 190 * operation. The atomicity guarantees that the new value is calculated based on
AnnaBridge 156:ff21514d8981 191 * up-to-date information; if the value had been updated by another thread in
AnnaBridge 156:ff21514d8981 192 * the meantime, the write would fail due to a mismatched expectedCurrentValue.
AnnaBridge 156:ff21514d8981 193 *
AnnaBridge 156:ff21514d8981 194 * Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect
AnnaBridge 156:ff21514d8981 195 * you to the article on compare-and swap].
AnnaBridge 156:ff21514d8981 196 *
AnnaBridge 156:ff21514d8981 197 * @param ptr The target memory location.
AnnaBridge 156:ff21514d8981 198 * @param[in,out] expectedCurrentValue A pointer to some location holding the
AnnaBridge 156:ff21514d8981 199 * expected current value of the data being set atomically.
AnnaBridge 156:ff21514d8981 200 * The computed 'desiredValue' should be a function of this current value.
AnnaBridge 156:ff21514d8981 201 * @note: This is an in-out parameter. In the
AnnaBridge 156:ff21514d8981 202 * failure case of atomic_cas (where the
AnnaBridge 156:ff21514d8981 203 * destination isn't set), the pointee of expectedCurrentValue is
AnnaBridge 156:ff21514d8981 204 * updated with the current value.
AnnaBridge 156:ff21514d8981 205 * @param[in] desiredValue The new value computed based on '*expectedCurrentValue'.
AnnaBridge 156:ff21514d8981 206 *
AnnaBridge 156:ff21514d8981 207 * @return true if the memory location was atomically
AnnaBridge 156:ff21514d8981 208 * updated with the desired value (after verifying
AnnaBridge 156:ff21514d8981 209 * that it contained the expectedCurrentValue),
AnnaBridge 156:ff21514d8981 210 * false otherwise. In the failure case,
AnnaBridge 156:ff21514d8981 211 * exepctedCurrentValue is updated with the new
AnnaBridge 156:ff21514d8981 212 * value of the target memory location.
AnnaBridge 156:ff21514d8981 213 *
AnnaBridge 156:ff21514d8981 214 * pseudocode:
AnnaBridge 156:ff21514d8981 215 * function cas(p : pointer to int, old : pointer to int, new : int) returns bool {
AnnaBridge 156:ff21514d8981 216 * if *p != *old {
AnnaBridge 156:ff21514d8981 217 * *old = *p
AnnaBridge 156:ff21514d8981 218 * return false
AnnaBridge 156:ff21514d8981 219 * }
AnnaBridge 156:ff21514d8981 220 * *p = new
AnnaBridge 156:ff21514d8981 221 * return true
AnnaBridge 156:ff21514d8981 222 * }
AnnaBridge 156:ff21514d8981 223 *
AnnaBridge 156:ff21514d8981 224 * @note: In the failure case (where the destination isn't set), the value
Anna Bridge 160:5571c4ff569f 225 * pointed to by expectedCurrentValue is instead updated with the current value.
AnnaBridge 156:ff21514d8981 226 * This property helps writing concise code for the following incr:
AnnaBridge 156:ff21514d8981 227 *
AnnaBridge 156:ff21514d8981 228 * function incr(p : pointer to int, a : int) returns int {
AnnaBridge 156:ff21514d8981 229 * done = false
AnnaBridge 156:ff21514d8981 230 * value = *p // This fetch operation need not be atomic.
AnnaBridge 156:ff21514d8981 231 * while not done {
AnnaBridge 156:ff21514d8981 232 * done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success
AnnaBridge 156:ff21514d8981 233 * }
AnnaBridge 156:ff21514d8981 234 * return value + a
AnnaBridge 156:ff21514d8981 235 * }
Anna Bridge 160:5571c4ff569f 236 *
Anna Bridge 160:5571c4ff569f 237 * @note: This corresponds to the C11 "atomic_compare_exchange_strong" - it
Anna Bridge 160:5571c4ff569f 238 * always succeeds if the current value is expected, as per the pseudocode
Anna Bridge 160:5571c4ff569f 239 * above; it will not spuriously fail as "atomic_compare_exchange_weak" may.
AnnaBridge 156:ff21514d8981 240 */
AnnaBridge 165:d1b4690b3f8b 241 bool core_util_atomic_cas_u16(volatile uint16_t *ptr, uint16_t *expectedCurrentValue, uint16_t desiredValue);
AnnaBridge 156:ff21514d8981 242
AnnaBridge 156:ff21514d8981 243 /**
AnnaBridge 156:ff21514d8981 244 * Atomic compare and set. It compares the contents of a memory location to a
AnnaBridge 156:ff21514d8981 245 * given value and, only if they are the same, modifies the contents of that
AnnaBridge 156:ff21514d8981 246 * memory location to a given new value. This is done as a single atomic
AnnaBridge 156:ff21514d8981 247 * operation. The atomicity guarantees that the new value is calculated based on
AnnaBridge 156:ff21514d8981 248 * up-to-date information; if the value had been updated by another thread in
AnnaBridge 156:ff21514d8981 249 * the meantime, the write would fail due to a mismatched expectedCurrentValue.
AnnaBridge 156:ff21514d8981 250 *
AnnaBridge 156:ff21514d8981 251 * Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect
AnnaBridge 156:ff21514d8981 252 * you to the article on compare-and swap].
AnnaBridge 156:ff21514d8981 253 *
AnnaBridge 156:ff21514d8981 254 * @param ptr The target memory location.
AnnaBridge 156:ff21514d8981 255 * @param[in,out] expectedCurrentValue A pointer to some location holding the
AnnaBridge 156:ff21514d8981 256 * expected current value of the data being set atomically.
AnnaBridge 156:ff21514d8981 257 * The computed 'desiredValue' should be a function of this current value.
AnnaBridge 156:ff21514d8981 258 * @note: This is an in-out parameter. In the
AnnaBridge 156:ff21514d8981 259 * failure case of atomic_cas (where the
AnnaBridge 156:ff21514d8981 260 * destination isn't set), the pointee of expectedCurrentValue is
AnnaBridge 156:ff21514d8981 261 * updated with the current value.
AnnaBridge 156:ff21514d8981 262 * @param[in] desiredValue The new value computed based on '*expectedCurrentValue'.
AnnaBridge 156:ff21514d8981 263 *
AnnaBridge 156:ff21514d8981 264 * @return true if the memory location was atomically
AnnaBridge 156:ff21514d8981 265 * updated with the desired value (after verifying
AnnaBridge 156:ff21514d8981 266 * that it contained the expectedCurrentValue),
AnnaBridge 156:ff21514d8981 267 * false otherwise. In the failure case,
AnnaBridge 156:ff21514d8981 268 * exepctedCurrentValue is updated with the new
AnnaBridge 156:ff21514d8981 269 * value of the target memory location.
AnnaBridge 156:ff21514d8981 270 *
AnnaBridge 156:ff21514d8981 271 * pseudocode:
AnnaBridge 156:ff21514d8981 272 * function cas(p : pointer to int, old : pointer to int, new : int) returns bool {
AnnaBridge 156:ff21514d8981 273 * if *p != *old {
AnnaBridge 156:ff21514d8981 274 * *old = *p
AnnaBridge 156:ff21514d8981 275 * return false
AnnaBridge 156:ff21514d8981 276 * }
AnnaBridge 156:ff21514d8981 277 * *p = new
AnnaBridge 156:ff21514d8981 278 * return true
AnnaBridge 156:ff21514d8981 279 * }
AnnaBridge 156:ff21514d8981 280 *
AnnaBridge 156:ff21514d8981 281 * @note: In the failure case (where the destination isn't set), the value
Anna Bridge 160:5571c4ff569f 282 * pointed to by expectedCurrentValue is instead updated with the current value.
AnnaBridge 156:ff21514d8981 283 * This property helps writing concise code for the following incr:
AnnaBridge 156:ff21514d8981 284 *
AnnaBridge 156:ff21514d8981 285 * function incr(p : pointer to int, a : int) returns int {
AnnaBridge 156:ff21514d8981 286 * done = false
AnnaBridge 156:ff21514d8981 287 * value = *p // This fetch operation need not be atomic.
AnnaBridge 156:ff21514d8981 288 * while not done {
AnnaBridge 156:ff21514d8981 289 * done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success
AnnaBridge 156:ff21514d8981 290 * }
AnnaBridge 156:ff21514d8981 291 * return value + a
Anna Bridge 160:5571c4ff569f 292 *
Anna Bridge 160:5571c4ff569f 293 * @note: This corresponds to the C11 "atomic_compare_exchange_strong" - it
Anna Bridge 160:5571c4ff569f 294 * always succeeds if the current value is expected, as per the pseudocode
Anna Bridge 160:5571c4ff569f 295 * above; it will not spuriously fail as "atomic_compare_exchange_weak" may.
AnnaBridge 156:ff21514d8981 296 * }
AnnaBridge 156:ff21514d8981 297 */
AnnaBridge 165:d1b4690b3f8b 298 bool core_util_atomic_cas_u32(volatile uint32_t *ptr, uint32_t *expectedCurrentValue, uint32_t desiredValue);
AnnaBridge 156:ff21514d8981 299
AnnaBridge 156:ff21514d8981 300 /**
AnnaBridge 156:ff21514d8981 301 * Atomic compare and set. It compares the contents of a memory location to a
AnnaBridge 156:ff21514d8981 302 * given value and, only if they are the same, modifies the contents of that
AnnaBridge 156:ff21514d8981 303 * memory location to a given new value. This is done as a single atomic
AnnaBridge 156:ff21514d8981 304 * operation. The atomicity guarantees that the new value is calculated based on
AnnaBridge 156:ff21514d8981 305 * up-to-date information; if the value had been updated by another thread in
AnnaBridge 156:ff21514d8981 306 * the meantime, the write would fail due to a mismatched expectedCurrentValue.
AnnaBridge 156:ff21514d8981 307 *
AnnaBridge 156:ff21514d8981 308 * Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect
AnnaBridge 156:ff21514d8981 309 * you to the article on compare-and swap].
AnnaBridge 156:ff21514d8981 310 *
AnnaBridge 156:ff21514d8981 311 * @param ptr The target memory location.
AnnaBridge 156:ff21514d8981 312 * @param[in,out] expectedCurrentValue A pointer to some location holding the
AnnaBridge 156:ff21514d8981 313 * expected current value of the data being set atomically.
AnnaBridge 156:ff21514d8981 314 * The computed 'desiredValue' should be a function of this current value.
AnnaBridge 156:ff21514d8981 315 * @note: This is an in-out parameter. In the
AnnaBridge 156:ff21514d8981 316 * failure case of atomic_cas (where the
AnnaBridge 156:ff21514d8981 317 * destination isn't set), the pointee of expectedCurrentValue is
AnnaBridge 156:ff21514d8981 318 * updated with the current value.
AnnaBridge 156:ff21514d8981 319 * @param[in] desiredValue The new value computed based on '*expectedCurrentValue'.
AnnaBridge 156:ff21514d8981 320 *
AnnaBridge 156:ff21514d8981 321 * @return true if the memory location was atomically
AnnaBridge 156:ff21514d8981 322 * updated with the desired value (after verifying
AnnaBridge 156:ff21514d8981 323 * that it contained the expectedCurrentValue),
AnnaBridge 156:ff21514d8981 324 * false otherwise. In the failure case,
AnnaBridge 156:ff21514d8981 325 * exepctedCurrentValue is updated with the new
AnnaBridge 156:ff21514d8981 326 * value of the target memory location.
AnnaBridge 156:ff21514d8981 327 *
AnnaBridge 156:ff21514d8981 328 * pseudocode:
AnnaBridge 156:ff21514d8981 329 * function cas(p : pointer to int, old : pointer to int, new : int) returns bool {
AnnaBridge 156:ff21514d8981 330 * if *p != *old {
AnnaBridge 156:ff21514d8981 331 * *old = *p
AnnaBridge 156:ff21514d8981 332 * return false
AnnaBridge 156:ff21514d8981 333 * }
AnnaBridge 156:ff21514d8981 334 * *p = new
AnnaBridge 156:ff21514d8981 335 * return true
AnnaBridge 156:ff21514d8981 336 * }
AnnaBridge 156:ff21514d8981 337 *
AnnaBridge 156:ff21514d8981 338 * @note: In the failure case (where the destination isn't set), the value
Anna Bridge 160:5571c4ff569f 339 * pointed to by expectedCurrentValue is instead updated with the current value.
AnnaBridge 156:ff21514d8981 340 * This property helps writing concise code for the following incr:
AnnaBridge 156:ff21514d8981 341 *
AnnaBridge 156:ff21514d8981 342 * function incr(p : pointer to int, a : int) returns int {
AnnaBridge 156:ff21514d8981 343 * done = false
AnnaBridge 156:ff21514d8981 344 * value = *p // This fetch operation need not be atomic.
AnnaBridge 156:ff21514d8981 345 * while not done {
AnnaBridge 156:ff21514d8981 346 * done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success
AnnaBridge 156:ff21514d8981 347 * }
AnnaBridge 156:ff21514d8981 348 * return value + a
AnnaBridge 156:ff21514d8981 349 * }
Anna Bridge 160:5571c4ff569f 350 *
Anna Bridge 160:5571c4ff569f 351 * @note: This corresponds to the C11 "atomic_compare_exchange_strong" - it
Anna Bridge 160:5571c4ff569f 352 * always succeeds if the current value is expected, as per the pseudocode
Anna Bridge 160:5571c4ff569f 353 * above; it will not spuriously fail as "atomic_compare_exchange_weak" may.
AnnaBridge 156:ff21514d8981 354 */
AnnaBridge 170:e95d10626187 355 bool core_util_atomic_cas_ptr(void *volatile *ptr, void **expectedCurrentValue, void *desiredValue);
AnnaBridge 156:ff21514d8981 356
AnnaBridge 156:ff21514d8981 357 /**
AnnaBridge 156:ff21514d8981 358 * Atomic increment.
AnnaBridge 156:ff21514d8981 359 * @param valuePtr Target memory location being incremented.
AnnaBridge 156:ff21514d8981 360 * @param delta The amount being incremented.
AnnaBridge 156:ff21514d8981 361 * @return The new incremented value.
AnnaBridge 156:ff21514d8981 362 */
AnnaBridge 165:d1b4690b3f8b 363 uint8_t core_util_atomic_incr_u8(volatile uint8_t *valuePtr, uint8_t delta);
AnnaBridge 156:ff21514d8981 364
AnnaBridge 156:ff21514d8981 365 /**
AnnaBridge 156:ff21514d8981 366 * Atomic increment.
AnnaBridge 156:ff21514d8981 367 * @param valuePtr Target memory location being incremented.
AnnaBridge 156:ff21514d8981 368 * @param delta The amount being incremented.
AnnaBridge 156:ff21514d8981 369 * @return The new incremented value.
AnnaBridge 156:ff21514d8981 370 */
AnnaBridge 165:d1b4690b3f8b 371 uint16_t core_util_atomic_incr_u16(volatile uint16_t *valuePtr, uint16_t delta);
AnnaBridge 156:ff21514d8981 372
AnnaBridge 156:ff21514d8981 373 /**
AnnaBridge 156:ff21514d8981 374 * Atomic increment.
AnnaBridge 156:ff21514d8981 375 * @param valuePtr Target memory location being incremented.
AnnaBridge 156:ff21514d8981 376 * @param delta The amount being incremented.
AnnaBridge 156:ff21514d8981 377 * @return The new incremented value.
AnnaBridge 156:ff21514d8981 378 */
AnnaBridge 165:d1b4690b3f8b 379 uint32_t core_util_atomic_incr_u32(volatile uint32_t *valuePtr, uint32_t delta);
AnnaBridge 156:ff21514d8981 380
AnnaBridge 156:ff21514d8981 381 /**
AnnaBridge 156:ff21514d8981 382 * Atomic increment.
AnnaBridge 156:ff21514d8981 383 * @param valuePtr Target memory location being incremented.
AnnaBridge 156:ff21514d8981 384 * @param delta The amount being incremented in bytes.
AnnaBridge 156:ff21514d8981 385 * @return The new incremented value.
AnnaBridge 156:ff21514d8981 386 *
AnnaBridge 156:ff21514d8981 387 * @note The type of the pointer argument is not taken into account
AnnaBridge 156:ff21514d8981 388 * and the pointer is incremented by bytes.
AnnaBridge 156:ff21514d8981 389 */
AnnaBridge 170:e95d10626187 390 void *core_util_atomic_incr_ptr(void *volatile *valuePtr, ptrdiff_t delta);
AnnaBridge 156:ff21514d8981 391
AnnaBridge 156:ff21514d8981 392 /**
AnnaBridge 156:ff21514d8981 393 * Atomic decrement.
AnnaBridge 156:ff21514d8981 394 * @param valuePtr Target memory location being decremented.
AnnaBridge 156:ff21514d8981 395 * @param delta The amount being decremented.
AnnaBridge 156:ff21514d8981 396 * @return The new decremented value.
AnnaBridge 156:ff21514d8981 397 */
AnnaBridge 165:d1b4690b3f8b 398 uint8_t core_util_atomic_decr_u8(volatile uint8_t *valuePtr, uint8_t delta);
AnnaBridge 156:ff21514d8981 399
AnnaBridge 156:ff21514d8981 400 /**
AnnaBridge 156:ff21514d8981 401 * Atomic decrement.
AnnaBridge 156:ff21514d8981 402 * @param valuePtr Target memory location being decremented.
AnnaBridge 156:ff21514d8981 403 * @param delta The amount being decremented.
AnnaBridge 156:ff21514d8981 404 * @return The new decremented value.
AnnaBridge 156:ff21514d8981 405 */
AnnaBridge 165:d1b4690b3f8b 406 uint16_t core_util_atomic_decr_u16(volatile uint16_t *valuePtr, uint16_t delta);
AnnaBridge 156:ff21514d8981 407
AnnaBridge 156:ff21514d8981 408 /**
AnnaBridge 156:ff21514d8981 409 * Atomic decrement.
AnnaBridge 156:ff21514d8981 410 * @param valuePtr Target memory location being decremented.
AnnaBridge 156:ff21514d8981 411 * @param delta The amount being decremented.
AnnaBridge 156:ff21514d8981 412 * @return The new decremented value.
AnnaBridge 156:ff21514d8981 413 */
AnnaBridge 165:d1b4690b3f8b 414 uint32_t core_util_atomic_decr_u32(volatile uint32_t *valuePtr, uint32_t delta);
AnnaBridge 156:ff21514d8981 415
AnnaBridge 156:ff21514d8981 416 /**
AnnaBridge 156:ff21514d8981 417 * Atomic decrement.
AnnaBridge 156:ff21514d8981 418 * @param valuePtr Target memory location being decremented.
AnnaBridge 156:ff21514d8981 419 * @param delta The amount being decremented in bytes.
AnnaBridge 156:ff21514d8981 420 * @return The new decremented value.
AnnaBridge 156:ff21514d8981 421 *
AnnaBridge 156:ff21514d8981 422 * @note The type of the pointer argument is not taken into account
AnnaBridge 156:ff21514d8981 423 * and the pointer is decremented by bytes
AnnaBridge 156:ff21514d8981 424 */
AnnaBridge 170:e95d10626187 425 void *core_util_atomic_decr_ptr(void *volatile *valuePtr, ptrdiff_t delta);
AnnaBridge 156:ff21514d8981 426
AnnaBridge 156:ff21514d8981 427 #ifdef __cplusplus
AnnaBridge 156:ff21514d8981 428 } // extern "C"
AnnaBridge 156:ff21514d8981 429 #endif
AnnaBridge 158:1c57384330a6 430 /**@}*/
AnnaBridge 156:ff21514d8981 431
AnnaBridge 158:1c57384330a6 432 /**@}*/
AnnaBridge 156:ff21514d8981 433
AnnaBridge 156:ff21514d8981 434 #endif // __MBED_UTIL_CRITICAL_H__
AnnaBridge 156:ff21514d8981 435
AnnaBridge 158:1c57384330a6 436
AnnaBridge 158:1c57384330a6 437