1289_ Implementation analysis of vtask suspend() interface in FreeRTOS

All learning summary ： GreyZhang/g_FreeRTOS: learning notes about FreeRTOS. (github.com)

Except for a few minor problems , The analysis was suspended for some time . Fortunately, I wrote more recently 2 Analysis of interfaces , Daily learning inertia does not stop . Take a look today vTaskSuspend() Interface implementation , It's the first time for me to recover .

First , This API Relevant functions can only be realized after the configuration takes effect . First , Enter critical protection , Prevent the impact of interruptions . Then get the task handle , Then remove the corresponding task from the ready task list . If you remove , The ready task list of the corresponding task priority is empty , Then you need to reset the linked list .

If the task is waiting for the event to happen , Then we should also deal with the related linked list relationship . When these two parts are finished , Add the task to the pending task list .

If the task is still waiting for notification , Then we should also deal with the waiting state .

This interface can be called from interrupts , Therefore, there may be situations where the scheduler does not run . Now , The next blocking contact time point needs to be reset , Prevent operation on the current task .

If the task to be suspended is the current task , It depends on whether the scheduler is running . If the scheduler is running , Then you need to perform a task scheduling . If the scheduler is not running , Need to see OS All tasks in have been suspended . If all tasks are suspended , At present TCB Pointer to NULL, Otherwise, request a context switch . This context switch has been analyzed before , In essence, it is the task with the highest priority that is ready , Give Way pxCurrentTCB Points to the highest priority task ready TCB.

This interface is still very simple , It can be well understood by combining several basic concepts of the operating system .