vsync / spinlock / caslock.h

Simple spinlock based on compare-and-swap (CAS).

CAS is implemented with vatomic32_cmpxchg or a variant.

Example:

#include <vsync/spinlock/caslock.h>
#include <vsync/common/assert.h>
#include <pthread.h>
#include <stdio.h>

#define N            12
#define EXPECTED_VAL N

caslock_t g_lock = CASLOCK_INIT();
vuint32_t g_x    = 0;
vuint32_t g_y    = 0;

void *
run(void *args)
{
    caslock_acquire(&g_lock);
    g_x++;
    g_y++;
    caslock_release(&g_lock);

    (void)args;
    return NULL;
}

int
main(void)
{
    pthread_t threads[N];

    for (vsize_t i = 0; i < N; i++) {
        pthread_create(&threads[i], NULL, run, (void *)i);
    }

    for (vsize_t i = 0; i < N; i++) {
        pthread_join(threads[i], NULL);
    }

    ASSERT(g_x == EXPECTED_VAL);
    ASSERT(g_x == g_y);
    printf("Final value %u\n", g_x);
    return 0;
}

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Macros

Macro	Description
CASLOCK_INIT	Initializer of caslock_t.

Macro CASLOCK_INIT

CASLOCK_INIT()

Initializer of caslock_t.

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Functions

Function	Description
caslock_init	Initializes the CAS lock.
caslock_acquire	Acquires the CAS lock.
caslock_tryacquire	Tries to acquire the CAS lock.
caslock_release	Releases the CAS lock.

Function caslock_init

static void caslock_init(caslock_t *l)

Initializes the CAS lock.

Parameters:

• l: address of caslock_t object.

Note: alternatively use CASLOCK_INIT.

Function caslock_acquire

static void caslock_acquire(caslock_t *l)

Acquires the CAS lock.

Parameters:

• l: address of caslock_t object.

Function caslock_tryacquire

static vbool_t caslock_tryacquire(caslock_t *l)

Tries to acquire the CAS lock.

Parameters:

• l: address of caslock_t object.

Returns: true, if lock is acquired successfully.

Returns: false, if failed to acquire the lock.

Function caslock_release

static void caslock_release(caslock_t *l)

Releases the CAS lock.

Parameters:

• l: address of caslock_t object.

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