rte_ticketlock.h

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/* SPDX-License-Identifier: BSD-3-Clause
 * Copyright(c) 2019 Arm Limited
 */

#ifndef _RTE_TICKETLOCK_H_
#define _RTE_TICKETLOCK_H_

#ifdef __cplusplus
extern "C" {
#endif

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

typedef union {
    uint32_t tickets;
    struct {
        uint16_t current;
        uint16_t next;
    } s;
} rte_ticketlock_t;

#define RTE_TICKETLOCK_INITIALIZER { 0 }

static inline __rte_experimental void
rte_ticketlock_init(rte_ticketlock_t *tl)
{
    __atomic_store_n(&tl->tickets, 0, __ATOMIC_RELAXED);
}

static inline __rte_experimental void
rte_ticketlock_lock(rte_ticketlock_t *tl)
{
    uint16_t me = __atomic_fetch_add(&tl->s.next, 1, __ATOMIC_RELAXED);
    while (__atomic_load_n(&tl->s.current, __ATOMIC_ACQUIRE) != me)
        rte_pause();
}

static inline __rte_experimental void
rte_ticketlock_unlock(rte_ticketlock_t *tl)
{
    uint16_t i = __atomic_load_n(&tl->s.current, __ATOMIC_RELAXED);
    __atomic_store_n(&tl->s.current, i + 1, __ATOMIC_RELEASE);
}

static inline __rte_experimental int
rte_ticketlock_trylock(rte_ticketlock_t *tl)
{
    rte_ticketlock_t old, new;
    old.tickets = __atomic_load_n(&tl->tickets, __ATOMIC_RELAXED);
    new.tickets = old.tickets;
    new.s.next++;
    if (old.s.next == old.s.current) {
        if (__atomic_compare_exchange_n(&tl->tickets, &old.tickets,
            new.tickets, 0, __ATOMIC_ACQUIRE, __ATOMIC_RELAXED))
            return 1;
    }

    return 0;
}

static inline __rte_experimental int
rte_ticketlock_is_locked(rte_ticketlock_t *tl)
{
    rte_ticketlock_t tic;
    tic.tickets = __atomic_load_n(&tl->tickets, __ATOMIC_ACQUIRE);
    return (tic.s.current != tic.s.next);
}

#define TICKET_LOCK_INVALID_ID -1

typedef struct {
    rte_ticketlock_t tl; 
    int user; 
    unsigned int count; 
} rte_ticketlock_recursive_t;

#define RTE_TICKETLOCK_RECURSIVE_INITIALIZER {RTE_TICKETLOCK_INITIALIZER, \
                          TICKET_LOCK_INVALID_ID, 0}

static inline __rte_experimental void
rte_ticketlock_recursive_init(rte_ticketlock_recursive_t *tlr)
{
    rte_ticketlock_init(&tlr->tl);
    __atomic_store_n(&tlr->user, TICKET_LOCK_INVALID_ID, __ATOMIC_RELAXED);
    tlr->count = 0;
}

static inline __rte_experimental void
rte_ticketlock_recursive_lock(rte_ticketlock_recursive_t *tlr)
{
    int id = rte_gettid();

    if (__atomic_load_n(&tlr->user, __ATOMIC_RELAXED) != id) {
        rte_ticketlock_lock(&tlr->tl);
        __atomic_store_n(&tlr->user, id, __ATOMIC_RELAXED);
    }
    tlr->count++;
}

static inline __rte_experimental void
rte_ticketlock_recursive_unlock(rte_ticketlock_recursive_t *tlr)
{
    if (--(tlr->count) == 0) {
        __atomic_store_n(&tlr->user, TICKET_LOCK_INVALID_ID,
                 __ATOMIC_RELAXED);
        rte_ticketlock_unlock(&tlr->tl);
    }
}

static inline __rte_experimental int
rte_ticketlock_recursive_trylock(rte_ticketlock_recursive_t *tlr)
{
    int id = rte_gettid();

    if (__atomic_load_n(&tlr->user, __ATOMIC_RELAXED) != id) {
        if (rte_ticketlock_trylock(&tlr->tl) == 0)
            return 0;
        __atomic_store_n(&tlr->user, id, __ATOMIC_RELAXED);
    }
    tlr->count++;
    return 1;
}

#ifdef __cplusplus
}
#endif

#endif /* _RTE_TICKETLOCK_H_ */