rte_rwlock.h

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/* SPDX-License-Identifier: BSD-3-Clause
 * Copyright(c) 2010-2014 Intel Corporation
 */

#ifndef _RTE_RWLOCK_H_
#define _RTE_RWLOCK_H_

#ifdef __cplusplus
extern "C" {
#endif

#include <rte_common.h>
#include <rte_atomic.h>
#include <rte_pause.h>

typedef struct {
        volatile int32_t cnt; 
} rte_rwlock_t;

#define RTE_RWLOCK_INITIALIZER { 0 }

static inline void
rte_rwlock_init(rte_rwlock_t *rwl)
{
        rwl->cnt = 0;
}

static inline void
rte_rwlock_read_lock(rte_rwlock_t *rwl)
{
        int32_t x;
        int success = 0;

        while (success == 0) {
                x = rwl->cnt;
                /* write lock is held */
                if (x < 0) {
                        rte_pause();
                        continue;
                }
                success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
                                              (uint32_t)x, (uint32_t)(x + 1));
        }
}

static inline __rte_experimental int
rte_rwlock_read_trylock(rte_rwlock_t *rwl)
{
        int32_t x;
        int success = 0;

        while (success == 0) {
                x = rwl->cnt;
                /* write lock is held */
                if (x < 0)
                        return -EBUSY;
                success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
                                              (uint32_t)x, (uint32_t)(x + 1));
        }
        return 0;
}

static inline void
rte_rwlock_read_unlock(rte_rwlock_t *rwl)
{
        rte_atomic32_dec((rte_atomic32_t *)(intptr_t)&rwl->cnt);
}

static inline __rte_experimental int
rte_rwlock_write_trylock(rte_rwlock_t *rwl)
{
        int32_t x;

        x = rwl->cnt;
        if (x != 0 || rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
                                0, (uint32_t)-1) == 0)
                return -EBUSY;

        return 0;
}

static inline void
rte_rwlock_write_lock(rte_rwlock_t *rwl)
{
        int32_t x;
        int success = 0;

        while (success == 0) {
                x = rwl->cnt;
                /* a lock is held */
                if (x != 0) {
                        rte_pause();
                        continue;
                }
                success = rte_atomic32_cmpset((volatile uint32_t *)&rwl->cnt,
                                              0, (uint32_t)-1);
        }
}

static inline void
rte_rwlock_write_unlock(rte_rwlock_t *rwl)
{
        rte_atomic32_inc((rte_atomic32_t *)(intptr_t)&rwl->cnt);
}

static inline void
rte_rwlock_read_lock_tm(rte_rwlock_t *rwl);

static inline void
rte_rwlock_read_unlock_tm(rte_rwlock_t *rwl);

static inline void
rte_rwlock_write_lock_tm(rte_rwlock_t *rwl);

static inline void
rte_rwlock_write_unlock_tm(rte_rwlock_t *rwl);

#ifdef __cplusplus
}
#endif

#endif /* _RTE_RWLOCK_H_ */