mutex.h

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/*
 * Copyright (c) 2019 Intel Corporation
 *
 * SPDX-License-Identifier: Apache-2.0
 */
 
#ifndef ZEPHYR_INCLUDE_SYS_MUTEX_H_
#define ZEPHYR_INCLUDE_SYS_MUTEX_H_
 
/*
 * sys_mutex behaves almost exactly like k_mutex, with the added advantage
 * that a sys_mutex instance can reside in user memory.
 *
 * Depending on CONFIG_SYS_MUTEX_IMPL, sys_mutex is implemented either via
 * a backing k_mutex (preserving priority inheritance) or via atomics on top
 * of k_futex (allowing uncontended lock/unlock without syscalls on archs
 * where reading the current thread and atomic ops are both syscall-free).
 *
 * Further enhancements will support priority inheritance with atomics once
 * a corresponding futex is available.
 */
 
#ifdef __cplusplus
extern "C" {
#endif
 
#ifdef CONFIG_USERSPACE
#include <zephyr/kernel.h>
#include <zephyr/sys/atomic.h>
#include <zephyr/types.h>
#include <zephyr/sys/clock.h>

struct sys_mutex {
#ifdef CONFIG_SYS_MUTEX_IMPL_K_MUTEX
        atomic_t val;
#elif defined(CONFIG_SYS_MUTEX_IMPL_FUTEX)
        struct k_futex futex;
        uint32_t counter;
#endif  /* CONFIG_SYS_MUTEX_IMPL_FUTEX */
};
 
#ifdef CONFIG_SYS_MUTEX_IMPL_K_MUTEX
__syscall int z_sys_mutex_kernel_lock(struct sys_mutex *mutex, k_timeout_t timeout);
 
__syscall int z_sys_mutex_kernel_unlock(struct sys_mutex *mutex);
 
#include <zephyr/syscalls/mutex.h>
#endif /* CONFIG_SYS_MUTEX_IMPL_K_MUTEX */


#if defined(CONFIG_SYS_MUTEX_IMPL_FUTEX)
#define SYS_MUTEX_DEFINE(name) struct sys_mutex name = {.futex = {0}, .counter = 0}
#else
#define SYS_MUTEX_DEFINE(name) struct sys_mutex name
#endif

void sys_mutex_init(struct sys_mutex *mutex);

int sys_mutex_lock(struct sys_mutex *mutex, k_timeout_t timeout);

int sys_mutex_unlock(struct sys_mutex *mutex);
 
#else
#include <zephyr/kernel.h>
 
struct sys_mutex {
        struct k_mutex kernel_mutex;
};
 
#define SYS_MUTEX_DEFINE(name) \
        struct sys_mutex name = { \
                .kernel_mutex = Z_MUTEX_INITIALIZER(name.kernel_mutex) \
        }
 
static inline void sys_mutex_init(struct sys_mutex *mutex)
{
        k_mutex_init(&mutex->kernel_mutex);
}
 
static inline int sys_mutex_lock(struct sys_mutex *mutex, k_timeout_t timeout)
{
        return k_mutex_lock(&mutex->kernel_mutex, timeout);
}
 
static inline int sys_mutex_unlock(struct sys_mutex *mutex)
{
        return k_mutex_unlock(&mutex->kernel_mutex);
}
 
#endif /* CONFIG_USERSPACE */

 
#ifdef __cplusplus
}
#endif
 
#endif /* ZEPHYR_INCLUDE_SYS_MUTEX_H_ */