Does the highest priority task run at all times?

bupthebroker wrote on Monday, May 09, 2016:

i read the scheduler pages but am still confused about if it is always the highest priority task in FreeRTOS that is executing? Or does the scheduler yield the highest priority task to give processing time to others as well?


rtel wrote on Monday, May 09, 2016:

By default, configUSE_TIME_SLICING is set to 1, and configUSE_PREEMPTION
is set to 1. When this is the case, the scheduler will always run the
highest priority task that is able to run. A task that is able to run
is a task that is not in the Blocked or Suspended state.

Therefore, if a low priority task is running when a high priority task
becomes able to run, then a switch to the higher priority task will
occur immediately. Also, while a higher priority task is running (is
not in the Blocked or Suspended state) all lower priority tasks will be
starved of processing time - which is why tasks must enter the Blocked

If there is more than one task at any given priority, and that priority
is the highest priority that has any tasks that are able to run, then
the scheduler will time slice the tasks - each time the tick interrupt
occurs it will switch to another task of equal priority.

bupthebroker wrote on Tuesday, May 10, 2016: