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a simple TaskYield question

Posted by htio on July 4, 2013
Hi,

just wondering if a context switching took place right before the TaskYield function, when it returns from the context switching will it execute the TaskYield (which will force another context switch again?), if so the task might be switched away twice in some random occasion and how do we prevent this from happening ?

please advise.

RE: a simple TaskYield question

Posted by Richard on July 4, 2013
The task has no knowledge of what the scheduler is doing. As far as it is concerned it is just executing a sequential piece of code.

The scheduler's job is to maintain the context of each task exactly as it switches the tasks in and out. It would be time consuming and a logical error for the scheduler to look ahead at what a task will do in the future and then try to change it.

Therefore there is nothing you can do about it, but a preemptive context switch will only occur if there is a task of higher priority that becomes available, or the timeslice used by the current task expires and there is a task of equal priority that is in the ready state.

Regards.

RE: a simple TaskYield question

Posted by htio on July 4, 2013
Hi, thanks for the reply, and yes i am having 2 task with the same priority and one with a TaskYield function in it, and i can see it sometimes skipped.


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