1288_ Implementation analysis of vtask resume() interface and interrupt Security version interface in FreeRTOS

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

The interface analysis in recent times may be relatively simple projects , The analysis went smoothly . Of course , It is also possible that the information read before has reached a certain amount, which is helpful for understanding these interfaces now .

This time, , Then analyze a simple interface vTaskResume().

It is worth noting that the above pretreatment , In fact, it is the same condition as the previous preprocessing of the interface that suspends tasks . The two processes have a little reverse meaning , It is also easy to understand why it exists at the same time .

Actually , Whether it exists at the same time is not very critical . The more valuable information for me is , These functions are actually not used in some projects I have been in contact with , Therefore, making modifications in this regard should ensure OS Cut to smaller size .

Back to the design and analysis of software code itself , First of all, it is judged here that the task to be resumed exists . In general , If the processing handle for the task is NULL It is usually the default to handle the current task , But this operation is not tenable in rationality analysis . therefore , A check assertion like this is added here .

The later part of the code is actually relatively simple , A very important point is that this operation should not deal with the current task . Because the current task must be running , If you want to do such a treatment, it must be meaningless . because , There is no possibility of suspending the currently running task . Another thing to note is the priority of the restored task , Because the task readiness with high priority may involve the processing of task scheduling .

About the task processing that really needs to be restored , First of all, the task is removed from the suspended list , Then add it to the ready task list . After adding , Determine the priority of the recovery task , After comparing with the current task priority, you can know whether the request processing of task scheduling is required next . Finally, handle the task scheduling request .

Interrupt the safe version of and normal API The main difference in processing lies in 2 spot . First of all , Interrupt the shielding of the Security version OS Interruption of custody ISR, Prevent interference . Another point , In fact, the suspension of processing tasks in interrupts does not need to consider whether the scheduler is suspended , In fact, they can be suspended , Even the current task. therefore , The task handle passed in is just to see if it is valid , I didn't judge whether it was a task being processed . And for the scheduler to hang , There is an extra linked list for temporary buffer , When the scheduler resumes, transfer the task to the ready task list .