uxTaskPriorityGet() for reading priority in FreeRTOS - Step-by-Step Execution

Concept Flow - uxTaskPriorityGet() for reading priority

Call uxTaskPriorityGet(taskHandle)

↓

Check if taskHandle is NULL?

No→Access task's priority

↓

Return task priority

↓

Return current task's priority

↓

Output priority value

The function checks if a task handle is given. If NULL, it returns the priority of the current task. Otherwise, it returns the priority of the specified task.

Execution Sample

FreeRTOS

TaskHandle_t myTask = xTaskGetCurrentTaskHandle();
UBaseType_t prio = uxTaskPriorityGet(myTask);
printf("Priority: %u\n", prio);

This code gets the current task handle, reads its priority using uxTaskPriorityGet(), and prints it.

Execution Table

Step	Input taskHandle	Check if NULL	Priority Accessed	Returned Priority	Output
1	myTask (valid handle)	No	Specified task's priority read	5	Priority: 5
2	NULL	Yes	Current task's priority read	5	Priority: 5
3	invalid handle	No	Undefined behavior (not shown)	-	-

💡 Function returns the priority of the given task or current task if NULL.

Variable Tracker

Variable	Start	After uxTaskPriorityGet call	Final
myTask	Valid task handle	Valid task handle	Valid task handle
prio	Undefined	5	5

Key Moments - 2 Insights

What happens if we pass NULL as the task handle?

If NULL is passed, uxTaskPriorityGet() returns the priority of the current running task, as shown in execution_table row 2.

Can uxTaskPriorityGet() be used with an invalid task handle?

No, passing an invalid handle leads to undefined behavior, which is not safe and not shown in the execution table.

Visual Quiz - 3 Questions

Look at the execution table, what priority is returned when passing a valid task handle?

A 5

B 0

C Undefined

D NULL

💡 Hint

See execution_table row 1 under 'Returned Priority' column.

At which step does the function return the current task's priority because the input is NULL?

A Step 1

B Step 3

C Step 2

D Never

💡 Hint

Check execution_table row 2 where 'Input taskHandle' is NULL.

If the variable 'prio' is 5 after the call, what was the likely input task handle?

A NULL

B Valid task handle

C Invalid handle

D Uninitialized

💡 Hint

Refer to variable_tracker and execution_table rows 1 and 2.

Concept Snapshot

uxTaskPriorityGet(taskHandle) returns the priority of the given task.
If taskHandle is NULL, it returns the current task's priority.
Priority is of type UBaseType_t (usually an unsigned int).
Passing invalid handles causes undefined behavior.
Use this to check task priority safely.

Full Transcript

The uxTaskPriorityGet() function reads the priority of a FreeRTOS task. When you call it with a task handle, it checks if the handle is NULL. If it is NULL, it returns the priority of the current running task. Otherwise, it returns the priority of the specified task. The priority is returned as an unsigned integer. Passing an invalid task handle is unsafe and can cause errors. This function helps you know the priority level of tasks in your system.