blob: 02977133f9525c2200806968eaa41323bb2754e7 [file] [log] [blame]
/*
* 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;
/**
*
* @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)
{
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;
}
/**
*
* @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)
{
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;
}
/**
*
* @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)
{
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;
}
/**
*
* @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)
{
k_spinlock_key_t key;
atomic_val_t ret;
key = k_spin_lock(&lock);
ret = *target;
(*target)++;
k_spin_unlock(&lock, 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)
{
k_spinlock_key_t key;
atomic_val_t ret;
key = k_spin_lock(&lock);
ret = *target;
(*target)--;
k_spin_unlock(&lock, 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)
{
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;
}
/**
*
* @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)
{
k_spinlock_key_t key;
atomic_val_t ret;
key = k_spin_lock(&lock);
ret = *target;
*target = 0;
k_spin_unlock(&lock, 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)
{
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;
}
/**
*
* @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)
{
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;
}
/**
*
* @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)
{
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;
}
/**
*
* @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)
{
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;
}