I had some strange behaviourwhen trying to use these functions. My main task (task1) was doing this: ~~~ vTaskSuspend(task2handle); … // store some variables that task2 will read vTaskResume(task2handle); ~~~ task2 has a higher priority than task1, and task2 spends most of its time waiting for an interrupt, by calling ulTaskNotifyTake. The ISR does this: ~~~ BaseTypet higherPriorityTaskWoken = pdFALSE; vTaskNotifyGiveFromISR(task2handle, &higherPriorityTaskWoken); portYIELDFROM_ISR(higherPriorityTaskWoken); ~~~ What I find it that if task1 runs in a loop making the suspend/resume call and doing other stuff as well, but never blocking, task2 doesn’t run. If I put a delay call in the task1 loop, then task2 runs sporadically. If I replace the vTaskSuspend call by taskENTERCRITICAL() and vTaskResume by taskEXITCRITICAL() then the program runs correctly, even without the delay call in the task1 loop. There is one more task in the system: task3, which has the same priority as task2 and also spends most of its time either waiting for an interrupt or delaying. What am I doing wrong? I was expecting vTaskSuspend and vTaskResume to behave similarly to taskENTERCRITICAL() and taskEXITCRITICAL() with respect to when task2 does and doesn’t run. In particular, if the interrupt occurs when task2 has been suspended by the call to vTaskSuspend(task2handle), I was expecting task2 to be scheduled when task1 makes the vTaskResume(task2handle) call. Or do I need to take some special action to tell the scheduler to schedule task2 if this happens, the same way I have to in the ISR? I’m using FreeRTOS 10.0.0 built for ARM_CM4F.

vTaskSuspend(task2handle); … // store some variables that task2 will read vTaskResume(task2handle); task2 has a higher priority than task1

So task 1 will only run when task 2 is blocked, presumably waiting on the notification – does the task block anywhere else?

, and task2 spends most of its time waiting for an interrupt, by calling ulTaskNotifyTake. The ISR does this: BaseTypet higherPriorityTaskWoken = pdFALSE; vTaskNotifyGiveFromISR(task2handle, &higherPriorityTaskWoken); portYIELDFROM_ISR(higherPriorityTaskWoken);

If task 2 is blocked waiting for a notification when it is suspended and then resumed, it will not return to wait for the notification again but simply exit the notify wait API function – you would then have to check the function’s return value to know if a notification was actually received. In this case I think you would be better protecting the area using a vTaskSuspendAll()/xTaskResumeAll() pair.