freertos_mutex_disinherit_test

Test for freertos task priority disinherit when mutex taking failed by a higher priority task.

The test code was modified from pico example : hello freertos.

The code is used to perform the test with a modified FreeRTOS kernel.

https://github.com/wirelinker/FreeRTOS-Kernel-for-test.git on branch mutex_disinherit_test

Use freertos_mutex_test.h to inject the test functions into tasks.c.

The specific test case and test functions are placed in freertos_mutex_test.c.

The test case is described below:

• only use single core.

• task1, pri=3

  • create and hold a mutex.
  • create task 2.

• task2, pri=4,

  • acquire mutex and make task1 inhirent pri=4.
  • block for a time period.

• task1, pri=4

  • change task2 pri=5.
  • Keep busying, so task1 can stay in Ready list.

• task2, pri=5

  • block timeout and wake up.

  • disinherit task1 priority back to '3' and remove task1 from pxReadyTasksLists[4].

  • the pxReadyTasksLists[4] is empty now.

  • portRESET_READY_PRIORITY() will clear priority '3' bit from uxTopReadyPriority.

  • At this moment, task1 hasn't been added back into Ready list.

  • So the valid highest priority of pxReadyTasksLists is only '5'.

  • Add task1 back to pxReadyTasksLists. The priority bit '3' be added back to uxTopReadyPriority.

The result would be:The pxReadyTasksLists[4] is empty. And the priority bit '4' will remain in uxTopReadyPriority. The next time, the scheduler may select a next task from the xListEnd.