pigweed / third_party / github / zephyrproject-rtos / zephyr / 22f22c2fc21ff1467f7f70d7d83ccdfb294538b4 / . / kernel / atomic_c.c

/* | |

* Copyright (c) 2016 Intel Corporation | |

* Copyright (c) 2011-2014 Wind River Systems, Inc. | |

* | |

* SPDX-License-Identifier: Apache-2.0 | |

*/ | |

/** | |

* @file Atomic ops in pure C | |

* | |

* This module provides the atomic operators for processors | |

* which do not support native atomic operations. | |

* | |

* The atomic operations are guaranteed to be atomic with respect | |

* to interrupt service routines, and to operations performed by peer | |

* processors. | |

* | |

* (originally from x86's atomic.c) | |

*/ | |

#include <atomic.h> | |

#include <toolchain.h> | |

#include <arch/cpu.h> | |

/** | |

* | |

* @brief Atomic compare-and-set primitive | |

* | |

* This routine provides the compare-and-set operator. If the original value at | |

* <target> equals <oldValue>, then <newValue> is stored at <target> and the | |

* function returns 1. | |

* | |

* If the original value at <target> does not equal <oldValue>, then the store | |

* is not done and the function returns 0. | |

* | |

* The reading of the original value at <target>, the comparison, | |

* and the write of the new value (if it occurs) all happen atomically with | |

* respect to both interrupts and accesses of other processors to <target>. | |

* | |

* @param target address to be tested | |

* @param old_value value to compare against | |

* @param new_value value to compare against | |

* @return Returns 1 if <new_value> is written, 0 otherwise. | |

*/ | |

int atomic_cas(atomic_t *target, atomic_val_t old_value, | |

atomic_val_t new_value) | |

{ | |

unsigned int key; | |

int ret = 0; | |

key = irq_lock(); | |

if (*target == old_value) { | |

*target = new_value; | |

ret = 1; | |

} | |

irq_unlock(key); | |

return ret; | |

} | |

/** | |

* | |

* @brief Atomic addition primitive | |

* | |

* This routine provides the atomic addition operator. The <value> is | |

* atomically added to the value at <target>, placing the result at <target>, | |

* and the old value from <target> is returned. | |

* | |

* @param target memory location to add to | |

* @param value the value to add | |

* | |

* @return The previous value from <target> | |

*/ | |

atomic_val_t atomic_add(atomic_t *target, atomic_val_t value) | |

{ | |

unsigned int key; | |

atomic_val_t ret; | |

key = irq_lock(); | |

ret = *target; | |

*target += value; | |

irq_unlock(key); | |

return ret; | |

} | |

/** | |

* | |

* @brief Atomic subtraction primitive | |

* | |

* This routine provides the atomic subtraction operator. The <value> is | |

* atomically subtracted from the value at <target>, placing the result at | |

* <target>, and the old value from <target> is returned. | |

* | |

* @param target the memory location to subtract from | |

* @param value the value to subtract | |

* | |

* @return The previous value from <target> | |

*/ | |

atomic_val_t atomic_sub(atomic_t *target, atomic_val_t value) | |

{ | |

unsigned int key; | |

atomic_val_t ret; | |

key = irq_lock(); | |

ret = *target; | |

*target -= value; | |

irq_unlock(key); | |

return ret; | |

} | |

/** | |

* | |

* @brief Atomic increment primitive | |

* | |

* @param target memory location to increment | |

* | |

* This routine provides the atomic increment operator. The value at <target> | |

* is atomically incremented by 1, and the old value from <target> is returned. | |

* | |

* @return The value from <target> before the increment | |

*/ | |

atomic_val_t atomic_inc(atomic_t *target) | |

{ | |

unsigned int key; | |

atomic_val_t ret; | |

key = irq_lock(); | |

ret = *target; | |

(*target)++; | |

irq_unlock(key); | |

return ret; | |

} | |

/** | |

* | |

* @brief Atomic decrement primitive | |

* | |

* @param target memory location to decrement | |

* | |

* This routine provides the atomic decrement operator. The value at <target> | |

* is atomically decremented by 1, and the old value from <target> is returned. | |

* | |

* @return The value from <target> prior to the decrement | |

*/ | |

atomic_val_t atomic_dec(atomic_t *target) | |

{ | |

unsigned int key; | |

atomic_val_t ret; | |

key = irq_lock(); | |

ret = *target; | |

(*target)--; | |

irq_unlock(key); | |

return ret; | |

} | |

/** | |

* | |

* @brief Atomic get primitive | |

* | |

* @param target memory location to read from | |

* | |

* This routine provides the atomic get primitive to atomically read | |

* a value from <target>. It simply does an ordinary load. Note that <target> | |

* is expected to be aligned to a 4-byte boundary. | |

* | |

* @return The value read from <target> | |

*/ | |

atomic_val_t atomic_get(const atomic_t *target) | |

{ | |

return *target; | |

} | |

/** | |

* | |

* @brief Atomic get-and-set primitive | |

* | |

* This routine provides the atomic set operator. The <value> is atomically | |

* written at <target> and the previous value at <target> is returned. | |

* | |

* @param target the memory location to write to | |

* @param value the value to write | |

* | |

* @return The previous value from <target> | |

*/ | |

atomic_val_t atomic_set(atomic_t *target, atomic_val_t value) | |

{ | |

unsigned int key; | |

atomic_val_t ret; | |

key = irq_lock(); | |

ret = *target; | |

*target = value; | |

irq_unlock(key); | |

return ret; | |

} | |

/** | |

* | |

* @brief Atomic clear primitive | |

* | |

* This routine provides the atomic clear operator. The value of 0 is atomically | |

* written at <target> and the previous value at <target> is returned. (Hence, | |

* atomic_clear(pAtomicVar) is equivalent to atomic_set(pAtomicVar, 0).) | |

* | |

* @param target the memory location to write | |

* | |

* @return The previous value from <target> | |

*/ | |

atomic_val_t atomic_clear(atomic_t *target) | |

{ | |

unsigned int key; | |

atomic_val_t ret; | |

key = irq_lock(); | |

ret = *target; | |

*target = 0; | |

irq_unlock(key); | |

return ret; | |

} | |

/** | |

* | |

* @brief Atomic bitwise inclusive OR primitive | |

* | |

* This routine provides the atomic bitwise inclusive OR operator. The <value> | |

* is atomically bitwise OR'ed with the value at <target>, placing the result | |

* at <target>, and the previous value at <target> is returned. | |

* | |

* @param target the memory location to be modified | |

* @param value the value to OR | |

* | |

* @return The previous value from <target> | |

*/ | |

atomic_val_t atomic_or(atomic_t *target, atomic_val_t value) | |

{ | |

unsigned int key; | |

atomic_val_t ret; | |

key = irq_lock(); | |

ret = *target; | |

*target |= value; | |

irq_unlock(key); | |

return ret; | |

} | |

/** | |

* | |

* @brief Atomic bitwise exclusive OR (XOR) primitive | |

* | |

* This routine provides the atomic bitwise exclusive OR operator. The <value> | |

* is atomically bitwise XOR'ed with the value at <target>, placing the result | |

* at <target>, and the previous value at <target> is returned. | |

* | |

* @param target the memory location to be modified | |

* @param value the value to XOR | |

* | |

* @return The previous value from <target> | |

*/ | |

atomic_val_t atomic_xor(atomic_t *target, atomic_val_t value) | |

{ | |

unsigned int key; | |

atomic_val_t ret; | |

key = irq_lock(); | |

ret = *target; | |

*target ^= value; | |

irq_unlock(key); | |

return ret; | |

} | |

/** | |

* | |

* @brief Atomic bitwise AND primitive | |

* | |

* This routine provides the atomic bitwise AND operator. The <value> is | |

* atomically bitwise AND'ed with the value at <target>, placing the result | |

* at <target>, and the previous value at <target> is returned. | |

* | |

* @param target the memory location to be modified | |

* @param value the value to AND | |

* | |

* @return The previous value from <target> | |

*/ | |

atomic_val_t atomic_and(atomic_t *target, atomic_val_t value) | |

{ | |

unsigned int key; | |

atomic_val_t ret; | |

key = irq_lock(); | |

ret = *target; | |

*target &= value; | |

irq_unlock(key); | |

return ret; | |

} | |

/** | |

* | |

* @brief Atomic bitwise NAND primitive | |

* | |

* This routine provides the atomic bitwise NAND operator. The <value> is | |

* atomically bitwise NAND'ed with the value at <target>, placing the result | |

* at <target>, and the previous value at <target> is returned. | |

* | |

* @param target the memory location to be modified | |

* @param value the value to NAND | |

* | |

* @return The previous value from <target> | |

*/ | |

atomic_val_t atomic_nand(atomic_t *target, atomic_val_t value) | |

{ | |

unsigned int key; | |

atomic_val_t ret; | |

key = irq_lock(); | |

ret = *target; | |

*target = ~(*target & value); | |

irq_unlock(key); | |

return ret; | |

} |