rtos - what kind of scheduler does FreeRTOS use? -

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what kind of scheduler freertos use.. read somewhere run complete scheduler, on other hand, i've seen being used parallel tasks, wouldn't round robin scheduler??

highest priority task granted cpu time. if multiple tasks have equal priority, uses round-robin scheduling among them. lower priority tasks must wait.

it important high priority tasks don't execute 100% of time, because lower priority tasks never cpu time. it's fundamental problem of real-time programming.

usually want assign high priority task must react fast important event, perform quick action , go sleep, letting less important stuff work in meantime.

generic example of such sustem may be:

  1. highest priority - device drivers tasks (valve control, adc, dac, etc)
  2. medium prio - administrative subsystem (console task, telnet task)
  3. lower priority - several application tasks (www server, data processing, etc)

lowest priority given general applications, scheduled using round-robin, gives more or less equal number of cpu time.

medium priority - console tasks. system operator cannot cut off malfunctioning www server gets stuck in infinite loop. tasks not running 100% of time. example may execute command-line commands administrator.

highest priority - device drivers, handling critical events, such machinery control. may interested in opening safety valve if boiler pressure gets high , don't want wait until stupid html rendering finished in webserver thread. such tasks run limited amount of time only.


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