cooperative multitasking scheme

Marco Bleekrode · 2004-09-19T09:32:19+00:00

Hi y'allQuick but not so easy question (it may spawn a considerable thread...)We need to develop a cooperative multitasking kernel for variousembedded platforms (See the implications and the complications?).One requirement is that c-functions should serve as "tasks". (Notably,these tasks perform very simple functions, e.g. polling push buttons,occasionally updating a display, polling an adc, and a whole slew ofother things that are definitely not time critical.)The question is, how should cpu time be distributed, given the following: Task 1: Priority 1 Task 2: Priority 1 Task 3: Priority 1 Task 4: Priority 1 Task 5: Priority 4 Task 6: Priority 8Should it be: T6 T6 T6 T6 T6 T6 T6 T6 T5 T5 T5 T5 T1 T2 T3 T4... ad infinitumor: T6 T5 T6 T5 T6 T5 T6 T5 T6 T1 T6 T2 T6 T3 T6 T4... ad infinitumor perhaps another scheme that does the assigned priorities right?A pointer would be very nice too, apart from an interesting discussion.None of us has a formal education in these matters... We are at amoderate loss...Thanks in advanceWaldemar

Sep 19, 2004 60 Replies

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Hans-Bernhard Broeker 22 years ago

[...]

Or because what they're doing *is* low-priority work, in the actual meaning of th word, i.e. it's not really important.

But changing scheduling algorithms wouldn't avoid that pitfall, it'd just change the symptoms: from a (starved) low-priority task not emptying the buffer to a (starved) high-priority task losing some of the input it's supposed to put into that buffer.

The general FUBAR character of the situation doesn't change one bit if you exchange the scheduler --- a "not enough CPU power available to do everything that needs to be done" condition doesn't go away all by itself.

Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de) Even if all the snow were burnt, ashes would remain.

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