doc(lab02): start doc for ex7

doc/lab-01_02.typ

@@ -150,7 +150,7 @@ license:        GPL
 description:    Module skeleton
 author:         Klagarge <remi@heredero.ch>
 author:         Fastium <fastium.pro@proton.me>
-depends:        
+depends:
 name:           mymodule
 vermagic:       5.15.148 SMP preempt mod_unload aarch64
 parm:           text:charp
@@ -332,13 +332,13 @@ for (int i = 0; i < elements; i++) {
       "temperature" = -1991 dot "register value" / 10 + 223000
     $
 
-    The chip ID can be verified in ```/proc/iomem```. 
-    The register value of the temperature can be verified in the file: ```/sys/class/thermal/thermal_zone0/temp```. 
+    The chip ID can be verified in ```/proc/iomem```.
+    The register value of the temperature can be verified in the file: ```/sys/class/thermal/thermal_zone0/temp```.
     The MAC address can be verified with ``` ifconfig```.
   ]
 )
 
-The resources are savec in a struct: 
+The resources are savec in a struct:
 ```c
 static struct resource* resources[3] = {[0] = 0,};
 ```
@@ -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
 //-------------------