Boot Linux faster!

Check our new training course

Boot Linux faster!

Check our new training course
and Creative Commons CC-BY-SA
lecture and lab materials

Bootlin logo

Elixir Cross Referencer

/* atomic operations */

/*
 * Copyright (c) 1997-2015, Wind River Systems, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef __ATOMIC_H__
#define __ATOMIC_H__

#ifdef __cplusplus
extern "C" {
#endif

typedef int atomic_t;
typedef atomic_t atomic_val_t;

extern atomic_val_t atomic_add(atomic_t *target, atomic_val_t value);
extern atomic_val_t atomic_and(atomic_t *target, atomic_val_t value);
extern atomic_val_t atomic_dec(atomic_t *target);
extern atomic_val_t atomic_inc(atomic_t *target);
extern atomic_val_t atomic_nand(atomic_t *target, atomic_val_t value);
extern atomic_val_t atomic_or(atomic_t *target, atomic_val_t value);
extern atomic_val_t atomic_sub(atomic_t *target, atomic_val_t value);
extern atomic_val_t atomic_xor(atomic_t *target, atomic_val_t value);
extern atomic_val_t atomic_clear(atomic_t *target);
extern atomic_val_t atomic_get(const atomic_t *target);
extern atomic_val_t atomic_set(atomic_t *target, atomic_val_t value);
extern int atomic_cas(atomic_t *target,
					  atomic_val_t oldValue, atomic_val_t newValue);


#define ATOMIC_INIT(i) {(i)}

#define ATOMIC_BITS (sizeof(atomic_val_t) * 8)
#define ATOMIC_MASK(bit) (1 << ((bit) & (ATOMIC_BITS - 1)))
#define ATOMIC_ELEM(addr, bit) ((addr) + ((bit) / ATOMIC_BITS))

/** @brief Test whether a bit is set
 *
 *  Test whether bit number bit is set or not.
 *
 *  Also works for an array of multiple atomic_t variables, in which
 *  case the bit number may go beyond the number of bits in a single
 *  atomic_t variable.
 *
 *  @param addr base address to start counting from
 *  @param bit bit number counted from the base address
 *
 *  @return 1 if the bit was set, 0 if it wasn't
 */
static inline int atomic_test_bit(const atomic_t *addr, int bit)
{
	atomic_val_t val = atomic_get(ATOMIC_ELEM(addr, bit));

	return (1 & (val >> (bit & (ATOMIC_BITS - 1))));
}

/** @brief Clear a bit and return its old value
 *
 *  Atomically clear a bit and return its old value.
 *
 *  Also works for an array of multiple atomic_t variables, in which
 *  case the bit number may go beyond the number of bits in a single
 *  atomic_t variable.
 *
 *  @param addr base address to start counting from
 *  @param bit bit number counted from the base address
 *
 *  @return 1 if the bit was set, 0 if it wasn't
 */
static inline int atomic_test_and_clear_bit(atomic_t *addr, int bit)
{
	atomic_val_t mask = ATOMIC_MASK(bit);
	atomic_val_t old;

	old = atomic_and(ATOMIC_ELEM(addr, bit), ~mask);

	return (old & mask) != 0;
}

/** @brief Set a bit and return its old value
 *
 *  Atomically set a bit and return its old value.
 *
 *  Also works for an array of multiple atomic_t variables, in which
 *  case the bit number may go beyond the number of bits in a single
 *  atomic_t variable.
 *
 *  @param addr base address to start counting from
 *  @param bit bit number counted from the base address
 *
 *  @return 1 if the bit was set, 0 if it wasn't
 */
static inline int atomic_test_and_set_bit(atomic_t *addr, int bit)
{
	atomic_val_t mask = ATOMIC_MASK(bit);
	atomic_val_t old;

	old = atomic_or(ATOMIC_ELEM(addr, bit), mask);

	return (old & mask) != 0;
}

/** @brief Clear a bit
 *
 *  Atomically clear a bit.
 *
 *  Also works for an array of multiple atomic_t variables, in which
 *  case the bit number may go beyond the number of bits in a single
 *  atomic_t variable.
 *
 *  @param addr base address to start counting from
 *  @param bit bit number counted from the base address
 */
static inline void atomic_clear_bit(atomic_t *addr, int bit)
{
	atomic_val_t mask = ATOMIC_MASK(bit);

	atomic_and(ATOMIC_ELEM(addr, bit), ~mask);
}

/** @brief Set a bit
 *
 *  Atomically set a bit.
 *
 *  Also works for an array of multiple atomic_t variables, in which
 *  case the bit number may go beyond the number of bits in a single
 *  atomic_t variable.
 *
 *  @param addr base address to start counting from
 *  @param bit bit number counted from the base address
 */
static inline void atomic_set_bit(atomic_t *addr, int bit)
{
	atomic_val_t mask = ATOMIC_MASK(bit);

	atomic_or(ATOMIC_ELEM(addr, bit), mask);
}

#ifdef __cplusplus
}
#endif

#endif /* __ATOMIC_H__ */