timer: mask interrupts in timer's timeout handler.

before running timer's timeout function, we need to make
sure that those threads waiting on this timer have been
added into the timer's wait queue, so add operations to
use timer lock to mask interrupts in z_timer_expiration_handler
function to synchronize timer's wait queue.

Signed-off-by: Chen Peng1 <peng1.chen@intel.com>

kernel/timer.c

@@ -26,6 +26,7 @@ void z_timer_expiration_handler(struct _timeout *t)
 {
 	struct k_timer *timer = CONTAINER_OF(t, struct k_timer, timeout);
 	struct k_thread *thread;
+	k_spinlock_key_t key = k_spin_lock(&lock);
 
 	/*
 	 * if the timer is periodic, start it again; don't add _TICK_ALIGN
@@ -46,27 +47,23 @@ void z_timer_expiration_handler(struct _timeout *t)
 	}
 
 	if (!IS_ENABLED(CONFIG_MULTITHREADING)) {
+		k_spin_unlock(&lock, key);
 		return;
 	}
 
 	thread = z_waitq_head(&timer->wait_q);
 
 	if (thread == NULL) {
+		k_spin_unlock(&lock, key);
 		return;
 	}
 
-	/*
-	 * Interrupts _DO NOT_ have to be locked in this specific
-	 * instance of thread unpending because a) this is the only
-	 * place a thread can be taken off this pend queue, and b) the
-	 * only place a thread can be put on the pend queue is at
-	 * thread level, which of course cannot interrupt the current
-	 * context.
-	 */
 	z_unpend_thread_no_timeout(thread);
 
 	arch_thread_return_value_set(thread, 0);
 
+	k_spin_unlock(&lock, key);
+
 	z_ready_thread(thread);
 }