BOARDIOC_SPINLOCK Spinlock Example

Overview

This example demonstrates the usage of the BOARDIOC_SPINLOCK board control interface for managing hardware spinlock operations in NuttX. The BOARDIOC_SPINLOCK interface provides a low-level mechanism to synchronize access to shared resources across multiple threads or CPUs using spinlock primitives.

What is BOARDIOC_SPINLOCK?

BOARDIOC_SPINLOCK is a board control request that allows applications to perform atomic spinlock operations through the boardctl() interface.

The BOARDIOC_SPINLOCK interface supports three primary operations:

BOARDIOC_SPINLOCK_LOCK - Acquire a spinlock (blocks until available)
BOARDIOC_SPINLOCK_TRYLOCK - Try to acquire a spinlock (non-blocking)
BOARDIOC_SPINLOCK_UNLOCK - Release a spinlock

Prerequisites

The following configuration options must be enabled:

# Enable board spinlock support
CONFIG_BOARDCTL_SPINLOCK=y

Basic Usage

Header Files

Include the following headers in your application:

#include <sys/boardctl.h>        /* For boardctl() interface */
#include <nuttx/spinlock.h>      /* For spinlock types */

Data Structures

The BOARDIOC_SPINLOCK interface uses the following structure:

struct boardioc_spinlock_s
{
    int action;                   /* Operation: LOCK, TRYLOCK, or UNLOCK */
    spinlock_t *lock;             /* Pointer to the spinlock variable */
    void *flags;                  /* Optional flags (reserved, set to NULL) */
};

Actions

The following action values are supported:

BOARDIOC_SPINLOCK_LOCK        /* Acquire lock (blocks if unavailable) */
BOARDIOC_SPINLOCK_TRYLOCK     /* Try to acquire (non-blocking) */
BOARDIOC_SPINLOCK_UNLOCK      /* Release lock */

Return Values

0 - Success
Negative value - Error code (converted to errno)

Simple Lock Example

Here’s a basic example of acquiring and releasing a spinlock:

spinlock_t my_lock;
struct boardioc_spinlock_s spinlock_op;
int ret;

/* Initialize the spinlock */
spin_lock_init(&my_lock);

/* Acquire the spinlock */
spinlock_op.action = BOARDIOC_SPINLOCK_LOCK;
spinlock_op.lock = &my_lock;
spinlock_op.flags = NULL;

ret = boardctl(BOARDIOC_SPINLOCK, (uintptr_t)&spinlock_op);
if (ret == 0) {
    printf("Spinlock acquired successfully\n");
} else {
    printf("Failed to acquire spinlock: %d\n", ret);
}

printf("Inside spinlock\n");

/* Release the spinlock */
spinlock_op.action = BOARDIOC_SPINLOCK_UNLOCK;
ret = boardctl(BOARDIOC_SPINLOCK, (uintptr_t)&spinlock_op);
if (ret == 0) {
    printf("Spinlock released successfully\n");
}