Bluetooth: Controller: Add development assert to check auxiliary parent

Add development assert to check the validity of auxiliary
context's parent. This is to ensure a released auxiliary
context is not reused without allocation.

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>

subsys/bluetooth/controller/ll_sw/ull_scan_aux.c

@@ -163,6 +163,7 @@ void ull_scan_aux_setup(memq_link_t *link, struct node_rx_hdr *rx)
 
 			/* aux parent will be NULL for periodic sync */
 			lll = aux->parent;
+			LL_ASSERT(lll);
 
 		} else if (!IS_ENABLED(CONFIG_BT_CTLR_SYNC_PERIODIC) ||
 			   ull_scan_is_valid_get(HDR_LLL2ULL(ftr->param))) {
@@ -190,6 +191,7 @@ void ull_scan_aux_setup(memq_link_t *link, struct node_rx_hdr *rx)
 
 			lll_aux = sync_lll->lll_aux;
 			aux = HDR_LLL2ULL(lll_aux);
+			LL_ASSERT(sync_lll == aux->parent);
 		}
 
 		if (!IS_ENABLED(CONFIG_BT_CTLR_SYNC_PERIODIC) || lll) {
@@ -756,8 +758,12 @@ void ull_scan_aux_done(struct node_rx_event_done *done)
 		aux = HDR_LLL2ULL(sync->lll.lll_aux);
 	} else {
 		struct ll_scan_set *scan;
+		struct lll_scan *lll;
 
-		scan = HDR_LLL2ULL(aux->parent);
+		lll = aux->parent;
+		LL_ASSERT(lll);
+
+		scan = HDR_LLL2ULL(lll);
 		LL_ASSERT(ull_scan_is_valid_get(scan));
 
 		/* Auxiliary context will be flushed by ull_scan_aux_stop() */
@@ -800,12 +806,17 @@ void *ull_scan_aux_lll_parent_get(struct lll_scan_aux *lll,
 				  uint8_t *is_lll_scan)
 {
 	struct ll_scan_aux_set *aux;
-	struct ll_scan_set *scan;
 
 	aux = HDR_LLL2ULL(lll);
-	scan = HDR_LLL2ULL(aux->parent);
 
 	if (is_lll_scan) {
+		struct ll_scan_set *scan;
+		struct lll_scan *lll;
+
+		lll = aux->parent;
+		LL_ASSERT(lll);
+
+		scan = HDR_LLL2ULL(lll);
 		*is_lll_scan = !!ull_scan_is_valid_get(scan);
 	}
 
@@ -884,6 +895,8 @@ void ull_scan_aux_release(memq_link_t *link, struct node_rx_hdr *rx)
 
 		aux = HDR_LLL2ULL(lll_aux);
 		lll = aux->parent;
+		LL_ASSERT(lll);
+
 		scan = HDR_LLL2ULL(lll);
 		scan = ull_scan_is_valid_get(scan);
 		if (scan) {
@@ -975,6 +988,8 @@ int ull_scan_aux_stop(struct ll_scan_aux_set *aux)
 		struct lll_scan *lll;
 
 		lll = aux->parent;
+		LL_ASSERT(lll);
+
 		scan = HDR_LLL2ULL(lll);
 		scan = ull_scan_is_valid_get(scan);
 		if (scan) {
@@ -1016,14 +1031,10 @@ static inline struct ll_scan_aux_set *aux_acquire(void)
 
 static inline void aux_release(struct ll_scan_aux_set *aux)
 {
-	/* Debug check that parent was assigned when allocated for reception of
-	 * auxiliary channel PDUs.
-	 */
-	LL_ASSERT(aux->parent);
-
 	/* Clear the parent so that when scan is being disabled then this
 	 * auxiliary context shall not associate itself from being disable.
 	 */
+	LL_ASSERT(aux->parent);
 	aux->parent = NULL;
 
 	mem_release(aux, &scan_aux_free);
@@ -1067,7 +1078,12 @@ static void flush(void *param)
 	struct lll_scan *lll;
 	bool sched = false;
 
+	/* Debug check that parent was assigned when allocated for reception of
+	 * auxiliary channel PDUs.
+	 */
 	aux = param;
+	LL_ASSERT(aux->parent);
+
 	rx = aux->rx_head;
 	if (rx) {
 		ll_rx_put(rx->link, rx);
@@ -1143,6 +1159,7 @@ static void aux_sync_incomplete(void *param)
 
 		/* get reference to sync context */
 		lll = aux->parent;
+		LL_ASSERT(lll);
 		sync = HDR_LLL2ULL(lll);
 
 		/* reset data len total */
@@ -1169,6 +1186,8 @@ static void aux_sync_incomplete(void *param)
 		aux->rx_head = rx;
 	}
 
+	LL_ASSERT(!ull_ref_get(&aux->ull));
+
 	flush(aux);
 #endif /* CONFIG_BT_CTLR_SYNC_PERIODIC */
 }
@@ -1219,6 +1238,8 @@ static void ticker_op_cb(uint32_t status, void *param)
 
 		aux = param;
 		sync_lll = aux->parent;
+		LL_ASSERT(sync_lll);
+
 		sync = HDR_LLL2ULL(sync_lll);
 		sync = ull_sync_is_valid_get(sync);
 	} else {