doc(lab02): start doc for ex7

doc/lab-01_02.typ

@@ -384,6 +384,15 @@ Easy exercice, a thread in the kernet is a `struct task_struct*` that can be cre
   ]
 )
 
+This exercice make 2 threads in concurrency with wait queue. Here the queue ware declare
+statically with the macro `DECLARE_WAIT_QUEUE_HEAD`.  Then for this exercice we use an atomic
+trigger with 2 queues. It important that the trigger is atomic or protected by mutex because
+there is concurrency. The wait queues are used to wait until the trigger has changed to keep
+synchronization between the threads.
+
+It is very important to add `kthread_should_stop()` as a condition to wake up queue, because if there is
+a problem during the implementation, we cannot kill the code.
+
 //-------------------
 // Exercise 8: Interrupts
 //-------------------