ctc8631 wrote on Tuesday, May 09, 2017:
Hello, I’m new freeRTOS learner,
I try to read v9.0 source code about task.c, and in idle task, it will call prvCheckTasksWaitingTermination()
I’m confused why in this function,
it already check there is need deleded task or not by while( uxDeletedTasksWaitingCleanUp > ( UBaseType_t ) 0U ),
Why still need to use xListIsEmpty = listLIST_IS_EMPTY( &xTasksWaitingTermination ); to check again,and Why it will use vTaskSuspendAll(); and xTaskResumeAll(); to protect listLIST_IS_EMPTY() I found the xTaskResumeAll(), it really takes times
Is there any reason? thanks =)
static void prvCheckTasksWaitingTermination( void )
{
/** THIS FUNCTION IS CALLED FROM THE RTOS IDLE TASK **/
#if ( INCLUDE_vTaskDelete == 1 )
{
BaseType_t xListIsEmpty;
/* ucTasksDeleted is used to prevent vTaskSuspendAll() being called
too often in the idle task. */
while( uxDeletedTasksWaitingCleanUp > ( UBaseType_t ) 0U )
{
vTaskSuspendAll();
{
xListIsEmpty = listLIST_IS_EMPTY( &xTasksWaitingTermination );
}
( void ) xTaskResumeAll();
if( xListIsEmpty == pdFALSE )
{
TCB_t *pxTCB;
taskENTER_CRITICAL();
{
pxTCB = ( TCB_t * ) listGET_OWNER_OF_HEAD_ENTRY( ( &xTasksWaitingTermination ) );
( void ) uxListRemove( &( pxTCB->xStateListItem ) );
--uxCurrentNumberOfTasks;
--uxDeletedTasksWaitingCleanUp;
}
taskEXIT_CRITICAL();
prvDeleteTCB( pxTCB );
}
else
{
mtCOVERAGE_TEST_MARKER();
}
}
}
#endif /* INCLUDE_vTaskDelete */
}