mirror of
https://github.com/zephyrproject-rtos/zephyr
synced 2025-09-11 03:33:00 +00:00
b3eb510f5c
Most CPUs have instructions like LOCK, LDREX/STREX, etc which allows for atomic operations without locking interrupts that can be invoked from user mode without complication. They typically use compiler builtin atomic operations, or custom assembly to implement them. However, some CPUs may lack these kinds of instructions, such as Cortex-M0 or some ARC. They use these C-based atomic operation implementations instead. Unfortunately these require grabbing a spinlock to ensure proper concurrency with other threads and ISRs. Hence, they will trigger an exception when called from user mode. For these platforms, which support user mode but not atomic operation instructions, the atomic API has been exposed as system calls. Some of the implementations in atomic_c.c which can be instead expressed in terms of other atomic operations have been removed. The kernel test of atomic operations now runs in user mode to prove that this works. Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
469 lines
12 KiB
C
469 lines
12 KiB
C
/* atomic operations */
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/*
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* Copyright (c) 1997-2015, Wind River Systems, Inc.
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#ifndef ZEPHYR_INCLUDE_ATOMIC_H_
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#define ZEPHYR_INCLUDE_ATOMIC_H_
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#include <stdbool.h>
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#include <toolchain.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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typedef int atomic_t;
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typedef atomic_t atomic_val_t;
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/**
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* @defgroup atomic_apis Atomic Services APIs
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* @ingroup kernel_apis
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* @{
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*/
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/**
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* @brief Atomic compare-and-set.
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*
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* This routine performs an atomic compare-and-set on @a target. If the current
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* value of @a target equals @a old_value, @a target is set to @a new_value.
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* If the current value of @a target does not equal @a old_value, @a target
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* is left unchanged.
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*
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* @param target Address of atomic variable.
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* @param old_value Original value to compare against.
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* @param new_value New value to store.
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* @return true if @a new_value is written, false otherwise.
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*/
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#ifdef CONFIG_ATOMIC_OPERATIONS_BUILTIN
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static inline bool atomic_cas(atomic_t *target, atomic_val_t old_value,
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atomic_val_t new_value)
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{
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return __atomic_compare_exchange_n(target, &old_value, new_value,
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0, __ATOMIC_SEQ_CST,
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__ATOMIC_SEQ_CST);
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}
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#elif defined(CONFIG_ATOMIC_OPERATIONS_C)
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__syscall int atomic_cas(atomic_t *target, atomic_val_t old_value,
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atomic_val_t new_value);
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#else
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extern int atomic_cas(atomic_t *target, atomic_val_t old_value,
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atomic_val_t new_value);
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#endif
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/**
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*
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* @brief Atomic addition.
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*
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* This routine performs an atomic addition on @a target.
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*
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* @param target Address of atomic variable.
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* @param value Value to add.
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*
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* @return Previous value of @a target.
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*/
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#ifdef CONFIG_ATOMIC_OPERATIONS_BUILTIN
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static inline atomic_val_t atomic_add(atomic_t *target, atomic_val_t value)
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{
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return __atomic_fetch_add(target, value, __ATOMIC_SEQ_CST);
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}
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#elif defined(CONFIG_ATOMIC_OPERATIONS_C)
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__syscall atomic_val_t atomic_add(atomic_t *target, atomic_val_t value);
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#else
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extern atomic_val_t atomic_add(atomic_t *target, atomic_val_t value);
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#endif
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/**
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*
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* @brief Atomic subtraction.
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*
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* This routine performs an atomic subtraction on @a target.
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*
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* @param target Address of atomic variable.
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* @param value Value to subtract.
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*
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* @return Previous value of @a target.
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*/
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#ifdef CONFIG_ATOMIC_OPERATIONS_BUILTIN
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static inline atomic_val_t atomic_sub(atomic_t *target, atomic_val_t value)
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{
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return __atomic_fetch_sub(target, value, __ATOMIC_SEQ_CST);
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}
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#elif defined(CONFIG_ATOMIC_OPERATIONS_C)
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__syscall atomic_val_t atomic_sub(atomic_t *target, atomic_val_t value);
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#else
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extern atomic_val_t atomic_sub(atomic_t *target, atomic_val_t value);
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#endif
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/**
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*
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* @brief Atomic increment.
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*
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* This routine performs an atomic increment by 1 on @a target.
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*
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* @param target Address of atomic variable.
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*
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* @return Previous value of @a target.
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*/
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#if defined(CONFIG_ATOMIC_OPERATIONS_BUILTIN) || defined (CONFIG_ATOMIC_OPERATIONS_C)
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static inline atomic_val_t atomic_inc(atomic_t *target)
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{
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return atomic_add(target, 1);
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}
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#else
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extern atomic_val_t atomic_inc(atomic_t *target);
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#endif
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/**
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*
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* @brief Atomic decrement.
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*
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* This routine performs an atomic decrement by 1 on @a target.
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*
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* @param target Address of atomic variable.
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*
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* @return Previous value of @a target.
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*/
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#if defined(CONFIG_ATOMIC_OPERATIONS_BUILTIN) || defined (CONFIG_ATOMIC_OPERATIONS_C)
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static inline atomic_val_t atomic_dec(atomic_t *target)
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{
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return atomic_sub(target, 1);
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}
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#else
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extern atomic_val_t atomic_dec(atomic_t *target);
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#endif
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/**
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*
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* @brief Atomic get.
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*
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* This routine performs an atomic read on @a target.
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*
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* @param target Address of atomic variable.
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*
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* @return Value of @a target.
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*/
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#ifdef CONFIG_ATOMIC_OPERATIONS_BUILTIN
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static inline atomic_val_t atomic_get(const atomic_t *target)
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{
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return __atomic_load_n(target, __ATOMIC_SEQ_CST);
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}
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#else
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extern atomic_val_t atomic_get(const atomic_t *target);
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#endif
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/**
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*
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* @brief Atomic get-and-set.
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*
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* This routine atomically sets @a target to @a value and returns
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* the previous value of @a target.
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*
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* @param target Address of atomic variable.
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* @param value Value to write to @a target.
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*
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* @return Previous value of @a target.
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*/
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#ifdef CONFIG_ATOMIC_OPERATIONS_BUILTIN
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static inline atomic_val_t atomic_set(atomic_t *target, atomic_val_t value)
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{
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/* This builtin, as described by Intel, is not a traditional
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* test-and-set operation, but rather an atomic exchange operation. It
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* writes value into *ptr, and returns the previous contents of *ptr.
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*/
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return __atomic_exchange_n(target, value, __ATOMIC_SEQ_CST);
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}
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#elif defined(CONFIG_ATOMIC_OPERATIONS_C)
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__syscall atomic_val_t atomic_set(atomic_t *target, atomic_val_t value);
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#else
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extern atomic_val_t atomic_set(atomic_t *target, atomic_val_t value);
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#endif
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/**
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*
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* @brief Atomic clear.
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*
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* This routine atomically sets @a target to zero and returns its previous
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* value. (Hence, it is equivalent to atomic_set(target, 0).)
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*
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* @param target Address of atomic variable.
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*
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* @return Previous value of @a target.
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*/
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#if defined(CONFIG_ATOMIC_OPERATIONS_BUILTIN) || defined (CONFIG_ATOMIC_OPERATIONS_C)
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static inline atomic_val_t atomic_clear(atomic_t *target)
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{
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return atomic_set(target, 0);
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}
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#else
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extern atomic_val_t atomic_clear(atomic_t *target);
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#endif
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/**
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*
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* @brief Atomic bitwise inclusive OR.
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*
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* This routine atomically sets @a target to the bitwise inclusive OR of
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* @a target and @a value.
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*
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* @param target Address of atomic variable.
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* @param value Value to OR.
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*
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* @return Previous value of @a target.
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*/
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#ifdef CONFIG_ATOMIC_OPERATIONS_BUILTIN
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static inline atomic_val_t atomic_or(atomic_t *target, atomic_val_t value)
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{
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return __atomic_fetch_or(target, value, __ATOMIC_SEQ_CST);
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}
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#elif defined(CONFIG_ATOMIC_OPERATIONS_C)
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__syscall atomic_val_t atomic_or(atomic_t *target, atomic_val_t value);
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#else
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extern atomic_val_t atomic_or(atomic_t *target, atomic_val_t value);
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#endif
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/**
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*
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* @brief Atomic bitwise exclusive OR (XOR).
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*
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* This routine atomically sets @a target to the bitwise exclusive OR (XOR) of
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* @a target and @a value.
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*
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* @param target Address of atomic variable.
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* @param value Value to XOR
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*
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* @return Previous value of @a target.
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*/
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#ifdef CONFIG_ATOMIC_OPERATIONS_BUILTIN
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static inline atomic_val_t atomic_xor(atomic_t *target, atomic_val_t value)
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{
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return __atomic_fetch_xor(target, value, __ATOMIC_SEQ_CST);
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}
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#elif defined(CONFIG_ATOMIC_OPERATIONS_C)
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__syscall atomic_val_t atomic_xor(atomic_t *target, atomic_val_t value);
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#else
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extern atomic_val_t atomic_xor(atomic_t *target, atomic_val_t value);
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#endif
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/**
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*
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* @brief Atomic bitwise AND.
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*
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* This routine atomically sets @a target to the bitwise AND of @a target
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* and @a value.
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*
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* @param target Address of atomic variable.
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* @param value Value to AND.
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*
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* @return Previous value of @a target.
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*/
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#ifdef CONFIG_ATOMIC_OPERATIONS_BUILTIN
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static inline atomic_val_t atomic_and(atomic_t *target, atomic_val_t value)
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{
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return __atomic_fetch_and(target, value, __ATOMIC_SEQ_CST);
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}
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#elif defined(CONFIG_ATOMIC_OPERATIONS_C)
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__syscall atomic_val_t atomic_and(atomic_t *target, atomic_val_t value);
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#else
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extern atomic_val_t atomic_and(atomic_t *target, atomic_val_t value);
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#endif
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/**
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*
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* @brief Atomic bitwise NAND.
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*
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* This routine atomically sets @a target to the bitwise NAND of @a target
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* and @a value. (This operation is equivalent to target = ~(target & value).)
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*
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* @param target Address of atomic variable.
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* @param value Value to NAND.
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*
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* @return Previous value of @a target.
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*/
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#ifdef CONFIG_ATOMIC_OPERATIONS_BUILTIN
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static inline atomic_val_t atomic_nand(atomic_t *target, atomic_val_t value)
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{
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return __atomic_fetch_nand(target, value, __ATOMIC_SEQ_CST);
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}
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#elif defined(CONFIG_ATOMIC_OPERATIONS_C)
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__syscall atomic_val_t atomic_nand(atomic_t *target, atomic_val_t value);
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#else
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extern atomic_val_t atomic_nand(atomic_t *target, atomic_val_t value);
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#endif
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/**
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* @brief Initialize an atomic variable.
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*
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* This macro can be used to initialize an atomic variable. For example,
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* @code atomic_t my_var = ATOMIC_INIT(75); @endcode
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*
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* @param i Value to assign to atomic variable.
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*/
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#define ATOMIC_INIT(i) (i)
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/**
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* @cond INTERNAL_HIDDEN
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*/
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#define ATOMIC_BITS (sizeof(atomic_val_t) * 8)
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#define ATOMIC_MASK(bit) (1 << ((bit) & (ATOMIC_BITS - 1)))
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#define ATOMIC_ELEM(addr, bit) ((addr) + ((bit) / ATOMIC_BITS))
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/**
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* INTERNAL_HIDDEN @endcond
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*/
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/**
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* @brief Define an array of atomic variables.
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*
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* This macro defines an array of atomic variables containing at least
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* @a num_bits bits.
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*
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* @note
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* If used from file scope, the bits of the array are initialized to zero;
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* if used from within a function, the bits are left uninitialized.
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*
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* @param name Name of array of atomic variables.
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* @param num_bits Number of bits needed.
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*/
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#define ATOMIC_DEFINE(name, num_bits) \
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atomic_t name[1 + ((num_bits) - 1) / ATOMIC_BITS]
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/**
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* @brief Atomically test a bit.
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*
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* This routine tests whether bit number @a bit of @a target is set or not.
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* The target may be a single atomic variable or an array of them.
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*
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* @param target Address of atomic variable or array.
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* @param bit Bit number (starting from 0).
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*
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* @return true if the bit was set, false if it wasn't.
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*/
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static inline bool atomic_test_bit(const atomic_t *target, int bit)
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{
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atomic_val_t val = atomic_get(ATOMIC_ELEM(target, bit));
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return (1 & (val >> (bit & (ATOMIC_BITS - 1)))) != 0;
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}
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/**
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* @brief Atomically test and clear a bit.
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*
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* Atomically clear bit number @a bit of @a target and return its old value.
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* The target may be a single atomic variable or an array of them.
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*
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* @param target Address of atomic variable or array.
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* @param bit Bit number (starting from 0).
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*
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* @return true if the bit was set, false if it wasn't.
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*/
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static inline bool atomic_test_and_clear_bit(atomic_t *target, int bit)
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{
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atomic_val_t mask = ATOMIC_MASK(bit);
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atomic_val_t old;
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old = atomic_and(ATOMIC_ELEM(target, bit), ~mask);
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return (old & mask) != 0;
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}
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/**
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* @brief Atomically set a bit.
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*
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* Atomically set bit number @a bit of @a target and return its old value.
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* The target may be a single atomic variable or an array of them.
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*
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* @param target Address of atomic variable or array.
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* @param bit Bit number (starting from 0).
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*
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* @return true if the bit was set, false if it wasn't.
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*/
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static inline bool atomic_test_and_set_bit(atomic_t *target, int bit)
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{
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atomic_val_t mask = ATOMIC_MASK(bit);
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atomic_val_t old;
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old = atomic_or(ATOMIC_ELEM(target, bit), mask);
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return (old & mask) != 0;
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}
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/**
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* @brief Atomically clear a bit.
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*
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* Atomically clear bit number @a bit of @a target.
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* The target may be a single atomic variable or an array of them.
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*
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* @param target Address of atomic variable or array.
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* @param bit Bit number (starting from 0).
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*
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* @return N/A
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*/
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static inline void atomic_clear_bit(atomic_t *target, int bit)
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{
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atomic_val_t mask = ATOMIC_MASK(bit);
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(void)atomic_and(ATOMIC_ELEM(target, bit), ~mask);
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}
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/**
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* @brief Atomically set a bit.
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*
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* Atomically set bit number @a bit of @a target.
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* The target may be a single atomic variable or an array of them.
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*
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* @param target Address of atomic variable or array.
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* @param bit Bit number (starting from 0).
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*
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* @return N/A
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*/
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static inline void atomic_set_bit(atomic_t *target, int bit)
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{
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atomic_val_t mask = ATOMIC_MASK(bit);
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(void)atomic_or(ATOMIC_ELEM(target, bit), mask);
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}
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/**
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* @brief Atomically set a bit to a given value.
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*
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* Atomically set bit number @a bit of @a target to value @a val.
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* The target may be a single atomic variable or an array of them.
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*
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* @param target Address of atomic variable or array.
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* @param bit Bit number (starting from 0).
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* @param val true for 1, false for 0.
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*
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* @return N/A
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*/
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static inline void atomic_set_bit_to(atomic_t *target, int bit, bool val)
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{
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atomic_val_t mask = ATOMIC_MASK(bit);
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if (val) {
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(void)atomic_or(ATOMIC_ELEM(target, bit), mask);
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} else {
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(void)atomic_and(ATOMIC_ELEM(target, bit), ~mask);
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}
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}
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#ifdef CONFIG_ATOMIC_OPERATIONS_C
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#include <syscalls/atomic.h>
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#endif
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/**
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* @}
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*/
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#ifdef __cplusplus
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}
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#endif
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#endif /* ZEPHYR_INCLUDE_ATOMIC_H_ */
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