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/*
* 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>
#include <spinlock.h>
/* Single global spinlock for atomic operations. This is fallback
* code, not performance sensitive. At least by not using irq_lock()
* in SMP contexts we won't content with legitimate users of the
* global lock.
*/
static struct k_spinlock lock;
/* For those rare CPUs which support user mode, but not native atomic
* operations, the best we can do for them is implement the atomic
* functions as system calls, since in user mode locking a spinlock is
* forbidden.
*/
#ifdef CONFIG_USERSPACE
#include <syscall_handler.h>
#define ATOMIC_SYSCALL_HANDLER_TARGET(name) \
Z_SYSCALL_HANDLER(name, target) { \
Z_OOPS(Z_SYSCALL_MEMORY_WRITE(target, sizeof(atomic_t))); \
return z_impl_##name((atomic_t *)target); \
}
#define ATOMIC_SYSCALL_HANDLER_TARGET_VALUE(name) \
Z_SYSCALL_HANDLER(name, target, value) { \
Z_OOPS(Z_SYSCALL_MEMORY_WRITE(target, sizeof(atomic_t))); \
return z_impl_##name((atomic_t *)target, value); \
}
#else
#define ATOMIC_SYSCALL_HANDLER_TARGET(name)
#define ATOMIC_SYSCALL_HANDLER_TARGET_VALUE(name)
#endif
/**
*
* @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 z_impl_atomic_cas(atomic_t *target, atomic_val_t old_value,
atomic_val_t new_value)
{
k_spinlock_key_t key;
int ret = 0;
key = k_spin_lock(&lock);
if (*target == old_value) {
*target = new_value;
ret = 1;
}
k_spin_unlock(&lock, key);
return ret;
}
#ifdef CONFIG_USERSPACE
Z_SYSCALL_HANDLER(atomic_cas, target, old_value, new_value)
{
Z_OOPS(Z_SYSCALL_MEMORY_WRITE(target, sizeof(atomic_t)));
return z_impl_atomic_cas((atomic_t *)target, old_value, new_value);
}
#endif /* CONFIG_USERSPACE */
/**
*
* @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 z_impl_atomic_add(atomic_t *target, atomic_val_t value)
{
k_spinlock_key_t key;
atomic_val_t ret;
key = k_spin_lock(&lock);
ret = *target;
*target += value;
k_spin_unlock(&lock, key);
return ret;
}
ATOMIC_SYSCALL_HANDLER_TARGET_VALUE(atomic_add);
/**
*
* @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 z_impl_atomic_sub(atomic_t *target, atomic_val_t value)
{
k_spinlock_key_t key;
atomic_val_t ret;
key = k_spin_lock(&lock);
ret = *target;
*target -= value;
k_spin_unlock(&lock, key);
return ret;
}
ATOMIC_SYSCALL_HANDLER_TARGET_VALUE(atomic_sub);
/**
*
* @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 z_impl_atomic_set(atomic_t *target, atomic_val_t value)
{
k_spinlock_key_t key;
atomic_val_t ret;
key = k_spin_lock(&lock);
ret = *target;
*target = value;
k_spin_unlock(&lock, key);
return ret;
}
ATOMIC_SYSCALL_HANDLER_TARGET_VALUE(atomic_set);
/**
*
* @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 z_impl_atomic_or(atomic_t *target, atomic_val_t value)
{
k_spinlock_key_t key;
atomic_val_t ret;
key = k_spin_lock(&lock);
ret = *target;
*target |= value;
k_spin_unlock(&lock, key);
return ret;
}
ATOMIC_SYSCALL_HANDLER_TARGET_VALUE(atomic_or);
/**
*
* @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 z_impl_atomic_xor(atomic_t *target, atomic_val_t value)
{
k_spinlock_key_t key;
atomic_val_t ret;
key = k_spin_lock(&lock);
ret = *target;
*target ^= value;
k_spin_unlock(&lock, key);
return ret;
}
ATOMIC_SYSCALL_HANDLER_TARGET_VALUE(atomic_xor);
/**
*
* @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 z_impl_atomic_and(atomic_t *target, atomic_val_t value)
{
k_spinlock_key_t key;
atomic_val_t ret;
key = k_spin_lock(&lock);
ret = *target;
*target &= value;
k_spin_unlock(&lock, key);
return ret;
}
ATOMIC_SYSCALL_HANDLER_TARGET_VALUE(atomic_and);
/**
*
* @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 z_impl_atomic_nand(atomic_t *target, atomic_val_t value)
{
k_spinlock_key_t key;
atomic_val_t ret;
key = k_spin_lock(&lock);
ret = *target;
*target = ~(*target & value);
k_spin_unlock(&lock, key);
return ret;
}
ATOMIC_SYSCALL_HANDLER_TARGET_VALUE(atomic_nand);