kernel: work_q: Fix k_work_queue_start documentation

Inform that the queue has to be initialized in zeroed memory or with
the k_work_queue_init before use.

Signed-off-by: Flavio Ceolin <[email protected]>

Author: Flavio Ceolin

doc/reference/kernel/threads/workqueue.rst

@@ -222,9 +222,11 @@ Defining and Controlling a Workqueue
 ====================================
 
 A workqueue is defined using a variable of type :c:struct:`k_work_q`.
-The workqueue is initialized by defining the stack area used by its thread
-and then calling :c:func:`k_work_queue_start`. The stack area must be defined
-using :c:macro:`K_THREAD_STACK_DEFINE` to ensure it is properly set up in
+The workqueue is initialized by defining the stack area used by its
+thread, initializing the :c:struct:`k_work_q`, either zeroing its
+memory or calling :c:func:`k_work_queue_init`, and then calling
+:c:func:`k_work_queue_start`. The stack area must be defined using
+:c:macro:`K_THREAD_STACK_DEFINE` to ensure it is properly set up in
 memory.
 
 The following code defines and initializes a workqueue:
@@ -238,6 +240,8 @@ The following code defines and initializes a workqueue:
 
     struct k_work_q my_work_q;
 
+    k_work_queue_init(&my_work_q);
+
     k_work_queue_start(&my_work_q, my_stack_area,
                        K_THREAD_STACK_SIZEOF(my_stack_area), MY_PRIORITY,
 		       NULL);

include/kernel.h

@@ -3061,7 +3061,9 @@ void k_work_queue_init(struct k_work_q *queue);
  * This configures the work queue thread and starts it running.  The function
  * should not be re-invoked on a queue.
  *
- * @param queue pointer to the queue structure.
+ * @param queue pointer to the queue structure. It must be initialized
+ *        in zeroed/bss memory or with @ref k_work_queue_init before
+ *        use.
  *
  * @param stack pointer to the work thread stack area.
  *