portability: cmsis: Fix possible race in osEventFlagsWait()

In osEventFlagsWait(), if an event raises after the call to k_event_wait()
and before the call to k_event_clear(), we may clear it while it is not
going to be report to the caller.

Reported-by: Rahul Gurram <[email protected]>
Signed-off-by: Jérôme Pouiller <[email protected]>

Author: jerome-pouiller

subsys/portability/cmsis_rtos_v2/event_flags.c

@@ -91,6 +91,7 @@ uint32_t osEventFlagsWait(osEventFlagsId_t ef_id, uint32_t flags, uint32_t optio
 			  uint32_t timeout)
 {
 	struct cmsis_rtos_event_cb *events = (struct cmsis_rtos_event_cb *)ef_id;
+	uint32_t sub_opt = options & (osFlagsWaitAll | osFlagsNoClear);
 	uint32_t rv;
 	k_timeout_t event_timeout;
 
@@ -114,14 +115,21 @@ uint32_t osEventFlagsWait(osEventFlagsId_t ef_id, uint32_t flags, uint32_t optio
 		event_timeout = K_TICKS(timeout);
 	}
 
-	if ((options & osFlagsWaitAll) != 0) {
+	switch (sub_opt) {
+	case osFlagsWaitAll | osFlagsNoClear:
 		rv = k_event_wait_all(&events->z_event, flags, false, event_timeout);
-	} else {
+		break;
+	case osFlagsWaitAll:
+		rv = k_event_wait_all_safe(&events->z_event, flags, false, event_timeout);
+		break;
+	case osFlagsNoClear:
 		rv = k_event_wait(&events->z_event, flags, false, event_timeout);
-	}
-
-	if ((options & osFlagsNoClear) == 0) {
-		k_event_clear(&events->z_event, flags);
+		break;
+	case 0:
+		rv = k_event_wait_safe(&events->z_event, flags, false, event_timeout);
+		break;
+	default:
+		__ASSERT_NO_MSG(0);
 	}
 
 	if (rv != 0U) {