mbed_critical.h

00001 
00002 /*
00003  * Copyright (c) 2015-2016, ARM Limited, All Rights Reserved
00004  * SPDX-License-Identifier: Apache-2.0
00005  *
00006  * Licensed under the Apache License, Version 2.0 (the "License"); you may
00007  * not use this file except in compliance with the License.
00008  * You may obtain a copy of the License at
00009  *
00010  * http://www.apache.org/licenses/LICENSE-2.0
00011  *
00012  * Unless required by applicable law or agreed to in writing, software
00013  * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
00014  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00015  * See the License for the specific language governing permissions and
00016  * limitations under the License.
00017  */
00018 
00019 #ifndef __MBED_UTIL_CRITICAL_H__
00020 #define __MBED_UTIL_CRITICAL_H__
00021 
00022 #include <stdbool.h>
00023 #include <stdint.h>
00024 #include <stddef.h>
00025 
00026 #ifdef __cplusplus
00027 extern "C" {
00028 #endif
00029 
00030 /** \addtogroup platform */
00031 /** @{*/
00032 /**
00033  * \defgroup platform_critical critical section function
00034  * @{
00035  */
00036 
00037 /** Determine the current interrupts enabled state
00038   *
00039   * This function can be called to determine whether or not interrupts are currently enabled.
00040   * @note
00041   * NOTE:
00042   * This function works for both cortex-A and cortex-M, although the underlyng implementation
00043   * differs.
00044   * @return true if interrupts are enabled, false otherwise
00045   */
00046 bool core_util_are_interrupts_enabled(void);
00047 
00048 /** Determine if this code is executing from an interrupt
00049   *
00050   * This function can be called to determine if the code is running on interrupt context.
00051   * @note
00052   * NOTE:
00053   * This function works for both cortex-A and cortex-M, although the underlyng implementation
00054   * differs.
00055   * @return true if in an isr, false otherwise
00056   */
00057 bool core_util_is_isr_active(void);
00058 
00059 /** Mark the start of a critical section
00060   *
00061   * This function should be called to mark the start of a critical section of code.
00062   * @note
00063   * NOTES:
00064   * 1) The use of this style of critical section is targetted at C based implementations.
00065   * 2) These critical sections can be nested.
00066   * 3) The interrupt enable state on entry to the first critical section (of a nested set, or single
00067   *    section) will be preserved on exit from the section.
00068   * 4) This implementation will currently only work on code running in privileged mode.
00069   */
00070 void core_util_critical_section_enter(void);
00071 
00072 /** Mark the end of a critical section
00073   *
00074   * This function should be called to mark the end of a critical section of code.
00075   * @note
00076   * NOTES:
00077   * 1) The use of this style of critical section is targetted at C based implementations.
00078   * 2) These critical sections can be nested.
00079   * 3) The interrupt enable state on entry to the first critical section (of a nested set, or single
00080   *    section) will be preserved on exit from the section.
00081   * 4) This implementation will currently only work on code running in privileged mode.
00082   */
00083 void core_util_critical_section_exit(void);
00084 
00085 /**
00086  * Atomic compare and set. It compares the contents of a memory location to a
00087  * given value and, only if they are the same, modifies the contents of that
00088  * memory location to a given new value. This is done as a single atomic
00089  * operation. The atomicity guarantees that the new value is calculated based on
00090  * up-to-date information; if the value had been updated by another thread in
00091  * the meantime, the write would fail due to a mismatched expectedCurrentValue.
00092  *
00093  * Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect
00094  * you to the article on compare-and swap].
00095  *
00096  * @param  ptr                  The target memory location.
00097  * @param[in,out] expectedCurrentValue A pointer to some location holding the
00098  *                              expected current value of the data being set atomically.
00099  *                              The computed 'desiredValue' should be a function of this current value.
00100  *                              @note: This is an in-out parameter. In the
00101  *                              failure case of atomic_cas (where the
00102  *                              destination isn't set), the pointee of expectedCurrentValue is
00103  *                              updated with the current value.
00104  * @param[in] desiredValue      The new value computed based on '*expectedCurrentValue'.
00105  *
00106  * @return                      true if the memory location was atomically
00107  *                              updated with the desired value (after verifying
00108  *                              that it contained the expectedCurrentValue),
00109  *                              false otherwise. In the failure case,
00110  *                              exepctedCurrentValue is updated with the new
00111  *                              value of the target memory location.
00112  *
00113  * pseudocode:
00114  * function cas(p : pointer to int, old : pointer to int, new : int) returns bool {
00115  *     if *p != *old {
00116  *         *old = *p
00117  *         return false
00118  *     }
00119  *     *p = new
00120  *     return true
00121  * }
00122  *
00123  * @note: In the failure case (where the destination isn't set), the value
00124  * pointed to by expectedCurrentValue is still updated with the current value.
00125  * This property helps writing concise code for the following incr:
00126  *
00127  * function incr(p : pointer to int, a : int) returns int {
00128  *     done = false
00129  *     value = *p // This fetch operation need not be atomic.
00130  *     while not done {
00131  *         done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success
00132  *     }
00133  *     return value + a
00134  * }
00135  */
00136 bool core_util_atomic_cas_u8(uint8_t *ptr, uint8_t *expectedCurrentValue, uint8_t desiredValue);
00137 
00138 /**
00139  * Atomic compare and set. It compares the contents of a memory location to a
00140  * given value and, only if they are the same, modifies the contents of that
00141  * memory location to a given new value. This is done as a single atomic
00142  * operation. The atomicity guarantees that the new value is calculated based on
00143  * up-to-date information; if the value had been updated by another thread in
00144  * the meantime, the write would fail due to a mismatched expectedCurrentValue.
00145  *
00146  * Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect
00147  * you to the article on compare-and swap].
00148  *
00149  * @param  ptr                  The target memory location.
00150  * @param[in,out] expectedCurrentValue A pointer to some location holding the
00151  *                              expected current value of the data being set atomically.
00152  *                              The computed 'desiredValue' should be a function of this current value.
00153  *                              @note: This is an in-out parameter. In the
00154  *                              failure case of atomic_cas (where the
00155  *                              destination isn't set), the pointee of expectedCurrentValue is
00156  *                              updated with the current value.
00157  * @param[in] desiredValue      The new value computed based on '*expectedCurrentValue'.
00158  *
00159  * @return                      true if the memory location was atomically
00160  *                              updated with the desired value (after verifying
00161  *                              that it contained the expectedCurrentValue),
00162  *                              false otherwise. In the failure case,
00163  *                              exepctedCurrentValue is updated with the new
00164  *                              value of the target memory location.
00165  *
00166  * pseudocode:
00167  * function cas(p : pointer to int, old : pointer to int, new : int) returns bool {
00168  *     if *p != *old {
00169  *         *old = *p
00170  *         return false
00171  *     }
00172  *     *p = new
00173  *     return true
00174  * }
00175  *
00176  * @note: In the failure case (where the destination isn't set), the value
00177  * pointed to by expectedCurrentValue is still updated with the current value.
00178  * This property helps writing concise code for the following incr:
00179  *
00180  * function incr(p : pointer to int, a : int) returns int {
00181  *     done = false
00182  *     value = *p // This fetch operation need not be atomic.
00183  *     while not done {
00184  *         done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success
00185  *     }
00186  *     return value + a
00187  * }
00188  */
00189 bool core_util_atomic_cas_u16(uint16_t *ptr, uint16_t *expectedCurrentValue, uint16_t desiredValue);
00190 
00191 /**
00192  * Atomic compare and set. It compares the contents of a memory location to a
00193  * given value and, only if they are the same, modifies the contents of that
00194  * memory location to a given new value. This is done as a single atomic
00195  * operation. The atomicity guarantees that the new value is calculated based on
00196  * up-to-date information; if the value had been updated by another thread in
00197  * the meantime, the write would fail due to a mismatched expectedCurrentValue.
00198  *
00199  * Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect
00200  * you to the article on compare-and swap].
00201  *
00202  * @param  ptr                  The target memory location.
00203  * @param[in,out] expectedCurrentValue A pointer to some location holding the
00204  *                              expected current value of the data being set atomically.
00205  *                              The computed 'desiredValue' should be a function of this current value.
00206  *                              @note: This is an in-out parameter. In the
00207  *                              failure case of atomic_cas (where the
00208  *                              destination isn't set), the pointee of expectedCurrentValue is
00209  *                              updated with the current value.
00210  * @param[in] desiredValue      The new value computed based on '*expectedCurrentValue'.
00211  *
00212  * @return                      true if the memory location was atomically
00213  *                              updated with the desired value (after verifying
00214  *                              that it contained the expectedCurrentValue),
00215  *                              false otherwise. In the failure case,
00216  *                              exepctedCurrentValue is updated with the new
00217  *                              value of the target memory location.
00218  *
00219  * pseudocode:
00220  * function cas(p : pointer to int, old : pointer to int, new : int) returns bool {
00221  *     if *p != *old {
00222  *         *old = *p
00223  *         return false
00224  *     }
00225  *     *p = new
00226  *     return true
00227  * }
00228  *
00229  * @note: In the failure case (where the destination isn't set), the value
00230  * pointed to by expectedCurrentValue is still updated with the current value.
00231  * This property helps writing concise code for the following incr:
00232  *
00233  * function incr(p : pointer to int, a : int) returns int {
00234  *     done = false
00235  *     value = *p // This fetch operation need not be atomic.
00236  *     while not done {
00237  *         done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success
00238  *     }
00239  *     return value + a
00240  * }
00241  */
00242 bool core_util_atomic_cas_u32(uint32_t *ptr, uint32_t *expectedCurrentValue, uint32_t desiredValue);
00243 
00244 /**
00245  * Atomic compare and set. It compares the contents of a memory location to a
00246  * given value and, only if they are the same, modifies the contents of that
00247  * memory location to a given new value. This is done as a single atomic
00248  * operation. The atomicity guarantees that the new value is calculated based on
00249  * up-to-date information; if the value had been updated by another thread in
00250  * the meantime, the write would fail due to a mismatched expectedCurrentValue.
00251  *
00252  * Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect
00253  * you to the article on compare-and swap].
00254  *
00255  * @param  ptr                  The target memory location.
00256  * @param[in,out] expectedCurrentValue A pointer to some location holding the
00257  *                              expected current value of the data being set atomically.
00258  *                              The computed 'desiredValue' should be a function of this current value.
00259  *                              @note: This is an in-out parameter. In the
00260  *                              failure case of atomic_cas (where the
00261  *                              destination isn't set), the pointee of expectedCurrentValue is
00262  *                              updated with the current value.
00263  * @param[in] desiredValue      The new value computed based on '*expectedCurrentValue'.
00264  *
00265  * @return                      true if the memory location was atomically
00266  *                              updated with the desired value (after verifying
00267  *                              that it contained the expectedCurrentValue),
00268  *                              false otherwise. In the failure case,
00269  *                              exepctedCurrentValue is updated with the new
00270  *                              value of the target memory location.
00271  *
00272  * pseudocode:
00273  * function cas(p : pointer to int, old : pointer to int, new : int) returns bool {
00274  *     if *p != *old {
00275  *         *old = *p
00276  *         return false
00277  *     }
00278  *     *p = new
00279  *     return true
00280  * }
00281  *
00282  * @note: In the failure case (where the destination isn't set), the value
00283  * pointed to by expectedCurrentValue is still updated with the current value.
00284  * This property helps writing concise code for the following incr:
00285  *
00286  * function incr(p : pointer to int, a : int) returns int {
00287  *     done = false
00288  *     value = *p // This fetch operation need not be atomic.
00289  *     while not done {
00290  *         done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success
00291  *     }
00292  *     return value + a
00293  * }
00294  */
00295 bool core_util_atomic_cas_ptr(void **ptr, void **expectedCurrentValue, void *desiredValue);
00296 
00297 /**
00298  * Atomic increment.
00299  * @param  valuePtr Target memory location being incremented.
00300  * @param  delta    The amount being incremented.
00301  * @return          The new incremented value.
00302  */
00303 uint8_t core_util_atomic_incr_u8(uint8_t *valuePtr, uint8_t delta);
00304 
00305 /**
00306  * Atomic increment.
00307  * @param  valuePtr Target memory location being incremented.
00308  * @param  delta    The amount being incremented.
00309  * @return          The new incremented value.
00310  */
00311 uint16_t core_util_atomic_incr_u16(uint16_t *valuePtr, uint16_t delta);
00312 
00313 /**
00314  * Atomic increment.
00315  * @param  valuePtr Target memory location being incremented.
00316  * @param  delta    The amount being incremented.
00317  * @return          The new incremented value.
00318  */
00319 uint32_t core_util_atomic_incr_u32(uint32_t *valuePtr, uint32_t delta);
00320 
00321 /**
00322  * Atomic increment.
00323  * @param  valuePtr Target memory location being incremented.
00324  * @param  delta    The amount being incremented in bytes.
00325  * @return          The new incremented value.
00326  *
00327  * @note The type of the pointer argument is not taken into account
00328  *       and the pointer is incremented by bytes.
00329  */
00330 void *core_util_atomic_incr_ptr(void **valuePtr, ptrdiff_t delta);
00331 
00332 /**
00333  * Atomic decrement.
00334  * @param  valuePtr Target memory location being decremented.
00335  * @param  delta    The amount being decremented.
00336  * @return          The new decremented value.
00337  */
00338 uint8_t core_util_atomic_decr_u8(uint8_t *valuePtr, uint8_t delta);
00339 
00340 /**
00341  * Atomic decrement.
00342  * @param  valuePtr Target memory location being decremented.
00343  * @param  delta    The amount being decremented.
00344  * @return          The new decremented value.
00345  */
00346 uint16_t core_util_atomic_decr_u16(uint16_t *valuePtr, uint16_t delta);
00347 
00348 /**
00349  * Atomic decrement.
00350  * @param  valuePtr Target memory location being decremented.
00351  * @param  delta    The amount being decremented.
00352  * @return          The new decremented value.
00353  */
00354 uint32_t core_util_atomic_decr_u32(uint32_t *valuePtr, uint32_t delta);
00355 
00356 /**
00357  * Atomic decrement.
00358  * @param  valuePtr Target memory location being decremented.
00359  * @param  delta    The amount being decremented in bytes.
00360  * @return          The new decremented value.
00361  *
00362  * @note The type of the pointer argument is not taken into account
00363  *       and the pointer is decremented by bytes
00364  */
00365 void *core_util_atomic_decr_ptr(void **valuePtr, ptrdiff_t delta);
00366 
00367 #ifdef __cplusplus
00368 } // extern "C"
00369 #endif
00370 /**@}*/
00371 
00372 /**@}*/
00373 
00374 #endif // __MBED_UTIL_CRITICAL_H__
00375 
00376 
00377