RT-Thread线程间同步(信号量, 互斥量, 事件集)--01API函数使用
系统间同步
RTThread提供的方式有信号量, 互斥量以及事件集
源码分析看下一篇源码分析
信号量
每个信号量对象都有一个信号量值和一个线程等待队列，信号量的值对应了信号量对象的实例数目、资源数目，假如信号量值为 5，则表示共有 5 个信号量实例（资源）可以被使用，当信号量实例数目为零时，再申请该信号量的线程就会被挂起在该信号量的等待队列上，等待可用的信号量实例
struct rt_semaphore
{
struct rt_ipc_object parent; /**< inherit from ipc_object 继承自ipc_object类*/
rt_uint16_t value; /**< value of semaphore. */
rt_uint16_t reserved; /**< reserved field 预留*/
};
typedef struct rt_semaphore *rt_sem_t;
实际使用
创建
/**
* This function will create a semaphore from system resource
*
* @param name the name of semaphore
* @param value the initial value of semaphore
* @param flag the flag of semaphore
*
* @return the created semaphore, RT_NULL on error happen
*
* @see rt_sem_init
*/
rt_sem_t rt_sem_create(const char *name, rt_uint32_t value, rt_uint8_t flag)
#define RT_IPC_FLAG_FIFO 0x00 /**< FIFOed IPC. @ref IPC. 按照先进先出的方式获取 */ #define RT_IPC_FLAG_PRIO 0x01 /**< PRIOed IPC. @ref IPC. 按照线程优先级 */
/**
* This function will initialize a semaphore and put it under control of
* resource management.
*
* @param sem the semaphore object
* @param name the name of semaphore
* @param value the initial value of semaphore
* @param flag the flag of semaphore
*
* @return the operation status, RT_EOK on successful
*/
rt_err_t rt_sem_init(rt_sem_t sem,
const char *name,
rt_uint32_t value,
rt_uint8_t flag)
删除
/**
* This function will delete a semaphore object and release the memory
*
* @param sem the semaphore object
*
* @return the error code
*
* @see rt_sem_detach
*/
rt_err_t rt_sem_delete(rt_sem_t sem)
系统将删除这个信号量。如果删除该信号量时，有线程正在等待该信号量，那么删除操作会先唤醒等待在该信号量上的线程（等待线程的返回值是-RT_ERROR），然后再释放信号量的内存资源。
/**
* This function will detach a semaphore from resource management
*
* @param sem the semaphore object
*
* @return the operation status, RT_EOK on successful
*
* @see rt_sem_delete
*/
rt_err_t rt_sem_detach(rt_sem_t sem)
获取
/**
* This function will take a semaphore, if the semaphore is unavailable, the
* thread shall wait for a specified time.
*
* @param sem the semaphore object
* @param time the waiting time
*
* @return the error code
*/
rt_err_t rt_sem_take(rt_sem_t sem, rt_int32_t time)
/**
* This function will try to take a semaphore and immediately return
*
* @param sem the semaphore object
*
* @return the error code
*/
rt_err_t rt_sem_trytake(rt_sem_t sem)
{
return rt_sem_take(sem, 0);
}
释放
/**
* This function will release a semaphore, if there are threads suspended on
* semaphore, it will be waked up.
*
* @param sem the semaphore object
*
* @return the error code
*/
rt_err_t rt_sem_release(rt_sem_t sem)
互斥量
拥有互斥量的线程拥有互斥量的所有权，互斥量支持递归访问且能防止线程优先级翻转；并且互斥量只能由持有线程释放，而信号量则可以由任何线程释放。
持有该互斥量的线程也能够再次获得这个锁而不被挂起(防止死锁)
这个实现了优先级继承(防止优先级翻转)
**注: **不可在中断里面使用
创建
/**
* This function will create a mutex from system resource
*
* @param name the name of mutex
* @param flag the flag of mutex
*
* @return the created mutex, RT_NULL on error happen
*
* @see rt_mutex_init
*/
rt_mutex_t rt_mutex_create(const char *name, rt_uint8_t flag)
/**
* This function will initialize a mutex and put it under control of resource
* management.
*
* @param mutex the mutex object
* @param name the name of mutex
* @param flag the flag of mutex
*
* @return the operation status, RT_EOK on successful
*/
rt_err_t rt_mutex_init(rt_mutex_t mutex, const char *name, rt_uint8_t flag)
flag可以是
#define RT_IPC_FLAG_FIFO 0x00 /**< FIFOed IPC. @ref IPC. 按照先进先出的方式获取 */ #define RT_IPC_FLAG_PRIO 0x01 /**< PRIOed IPC. @ref IPC. 按照线程优先级 */
删除
/**
* This function will delete a mutex object and release the memory
*
* @param mutex the mutex object
*
* @return the error code
*
* @see rt_mutex_detach
*/
rt_err_t rt_mutex_delete(rt_mutex_t mutex)
/**
* This function will detach a mutex from resource management
*
* @param mutex the mutex object
*
* @return the operation status, RT_EOK on successful
*
* @see rt_mutex_delete
*/
rt_err_t rt_mutex_detach(rt_mutex_t mutex)
会唤醒所有的睡眠的函数
获取
/*
* This function will take a mutex, if the mutex is unavailable, the
* thread shall wait for a specified time.
*
* @param mutex the mutex object
* @param time the waiting time
*
* @return the error code
*/
rt_err_t rt_mutex_take(rt_mutex_t mutex, rt_int32_t time)
释放
/**
* This function will release a mutex, if there are threads suspended on mutex,
* it will be waked up.
*
* @param mutex the mutex object
*
* @return the error code
*/
rt_err_t rt_mutex_release(rt_mutex_t mutex)
事件集
一个事件集可以包含多个事件，利用事件集可以完成一对多，多对多的线程间同步。
其中任意一个事件唤醒 线程，或几个事件都到达后唤醒线程，多个事件集合可以用一个32bit无符号整型变量来表示
- 事件只与线程相关，事件间相互独立
- 事件仅用于同步，不提供数据传输功能
- 事件无排队性，即多次向线程发送同一事件(如果线程还未来得及读走)，其效果等同于只发送一次
/*
* event structure
*/
struct rt_event
{
struct rt_ipc_object parent; /**< inherit from ipc_object */
rt_uint32_t set; /**< event set */
};
实际使用
创建和删除
/**
* This function will create an event object from system resource
*
* @param name the name of event
* @param flag the flag of event RT_IPC_FLAG_FIFO RT_IPC_FLAG_PRIO
*
* @return the created event, RT_NULL on error happen
*/
rt_event_t rt_event_create(const char *name, rt_uint8_t flag)
/**
* This function will delete an event object and release the memory
*
* @param event the event object
*
* @return the error code
*/
rt_err_t rt_event_delete(rt_event_t event)
/**
* This function will initialize an event and put it under control of resource
* management.
*
* @param event the event object
* @param name the name of event
* @param flag the flag of event
*
* @return the operation status, RT_EOK on successful
*/
rt_err_t rt_event_init(rt_event_t event, const char *name, rt_uint8_t flag)
/**
* This function will detach an event object from resource management
*
* @param event the event object
*
* @return the operation status, RT_EOK on successful
*/
rt_err_t rt_event_detach(rt_event_t event)
发送事件
/**
* This function will send an event to the event object, if there are threads
* suspended on event object, it will be waked up.
*
* @param event the event object
* @param set the event set
*
* @return the error code
*/
rt_err_t rt_event_send(rt_event_t event, rt_uint32_t set)
接收事件集
/**
* This function will receive an event from event object, if the event is
* unavailable, the thread shall wait for a specified time.
*
* @param event the fast event object
* @param set the interested event set
* @param option the receive option, either RT_EVENT_FLAG_AND or
* RT_EVENT_FLAG_OR should be set. RT_EVENT_FLAG_CLEAR
* @param timeout the waiting time RT_WAITING_FOREVER RT_WAITING_NO
* @param recved the received event, if you don't care, RT_NULL can be set.
*
* @return the error code
*/
rt_err_t rt_event_recv(rt_event_t event,
rt_uint32_t set,
rt_uint8_t option,
rt_int32_t timeout,
rt_uint32_t *recved)