taskENTER_CRITICAL_FROM_ISR()
taskEXIT_CRITICAL_FROM_ISR()
[RTOS 内核控制]

task. h

UBaseType_t taskENTER_CRITICAL_FROM_ISR( void );
void taskEXIT_CRITICAL_FROM_ISR( UBaseType_t uxSavedInterruptStatus );

taskENTER_CRITICAL() and taskEXIT_CRITICAL() 版本 可用于中断服务程序 (ISR)。

在 ISR 中，通过调用 taskENTER_CRITICAL_FROM_ISR() 进入临界区， 然后通过调用 taskEXIT_CRITICAL_FROM_ISR() 退出。

taskENTER_CRITICAL_FROM_ISR() 宏和 taskEXIT_CRITICAL_FROM_ISR() 宏提供了 基本临界区的实现，只需禁用中断即可使其全局运作， 可以是全局禁用，也可以是禁用到特定的中断优先级。

如果使用的 FreeRTOS 移植支持中断嵌套，则调用 taskENTER_CRITICAL_FROM_ISR() 将在内核配置常量 configMAX_SYSCALL_INTERRUPT_PRIORITY 设置的中断优先级或以下级别禁用中断，并 启用所有其他中断优先级。 如果使用的 FreeRTOS 移植不支持中断嵌套，则 taskENTER_CRITICAL_FROM_ISR() 和 taskEXIT_CRITICAL_FROM_ISR() 将不起作用。

调用 taskENTER_CRITICAL_FROM_ISR() 和 taskEXIT_CRITICAL_FROM_ISR() 旨在用于嵌套，但宏的使用方式的语义不同于 taskENTER_CRITICAL() 和 taskEXIT_CRITICAL() 等效项。

临界区必须保持非常短，否则将影响 更高优先级的中断的响应时间，会导致该中断嵌套。 每次 taskENTER_CRITICAL_FROM_ISR() 调用都必须紧密配合 taskEXIT_CRITICAL_FROM_ISR() 调用一起使用。

不得从临界区调用 FreeRTOS API 函数。

参数：

uxSavedInterruptStatus

taskEXIT_CRITICAL_FROM_ISR() 将 uxSavedInterruptStatus 作为其 唯一参数。 作为 uxSavedInterruptStatus 参数使用的值 必须是从匹配的 taskENTER_CRITICAL_FROM_ISR() 调用返回的值。 taskENTER_CRITICAL_FROM_ISR() 不采用任何 参数。

返回：

taskENTER_CRITICAL_FROM_ISR() 返回调用宏之前的中断掩码状态 。 taskENTER_CRITICAL_FROM_ISR() 返回的值 必须作为 uxSavedInterruptStatus 参数用于匹配的 taskEXIT_CRITICAL_FROM_ISR() 调用。

taskEXIT_CRITICAL_FROM_ISR() 不返回值。

/* A function called from an ISR. */
void vDemoFunction( void )
{
UBaseType_t uxSavedInterruptStatus;

    /* Enter the critical section.  In this example, this function is itself called from
    within a critical section, so entering this critical section will result in a nesting
    depth of 2. Save the value returned by taskENTER_CRITICAL_FROM_ISR() into a local
    stack variable so it can be passed into taskEXIT_CRITICAL_FROM_ISR(). */
    uxSavedInterruptStatus = taskENTER_CRITICAL_FROM_ISR();

    /* Perform the action that is being protected by the critical section here. */

    /* Exit the critical section.  In this example, this function is itself called from a
    critical section, so interrupts will have already been disabled before a value was
    stored in uxSavedInterruptStatus, and therefore passing uxSavedInterruptStatus into
    taskEXIT_CRITICAL_FROM_ISR() will not result in interrupts being re-enabled. */
    taskEXIT_CRITICAL_FROM_ISR( uxSavedInterruptStatus );
}

/* A task that calls vDemoFunction() from within an interrupt service routine. */
void vDemoISR( void )
{
UBaseType_t uxSavedInterruptStatus;

    /* Call taskENTER_CRITICAL_FROM_ISR() to create a critical section, saving the
    returned value into a local stack variable. */
    uxSavedInterruptStatus = taskENTER_CRITICAL_FROM_ISR();


    /* Execute the code that requires the critical section here. */


    /* Calls to taskENTER_CRITICAL_FROM_ISR() can be nested so it is safe to call a
    function that includes its own calls to taskENTER_CRITICAL_FROM_ISR() and
    taskEXIT_CRITICAL_FROM_ISR(). */
    vDemoFunction();

    /* The operation that required the critical section is complete so exit the
    critical section.  Assuming interrupts were enabled on entry to this ISR, the value
    saved in uxSavedInterruptStatus will result in interrupts being re-enabled.*/
    taskEXIT_CRITICAL_FROM_ISR( uxSavedInterruptStatus );
}