foreach_ll_safe

lib/core/context.c

@@ -1851,7 +1851,7 @@ lws_check_deferred_free(struct lws_context *context, int tsi, int force)
 
 	lws_context_lock(context, "check deferred free"); /* ------ context { */
 
-	lws_start_foreach_ll(struct lws_vhost *, v, context->vhost_list) {
+	lws_start_foreach_ll_safe(struct lws_vhost *, v, context->vhost_list, vhost_next) {
 		if (v->being_destroyed
 #if LWS_MAX_SMP > 1
 			&& !v->close_flow_vs_tsi[tsi]
@@ -1882,7 +1882,7 @@ lws_check_deferred_free(struct lws_context *context, int tsi, int force)
 
 			lws_pt_unlock(pt); /* } pt -------------- */
 		}
-	} lws_end_foreach_ll(v, vhost_next);
+	} lws_end_foreach_ll_safe(v);
 
 
 	lws_context_unlock(context); /* } context ------------------- */

lib/libwebsockets.h

@@ -5485,6 +5485,42 @@ lws_interface_to_sa(int ipv6, const char *ifname, struct sockaddr_in *addr,
 	} \
 }
 
+/**
+ * lws_start_foreach_ll_safe(): linkedlist iterator helper start safe against delete
+ *
+ * \param type: type of iteration, eg, struct xyz *
+ * \param it: iterator var name to create
+ * \param start: start of list
+ * \param nxt: member name in the iterator pointing to next list element
+ *
+ * This helper creates an iterator and starts a while (it) {
+ * loop.  The iterator runs through the linked list starting at start and
+ * ends when it gets a NULL.
+ * The while loop should be terminated using lws_end_foreach_ll_safe().
+ * Performs storage of next increment for situations where iterator can become invalidated
+ * during iteration.
+ */
+#define lws_start_foreach_ll_safe(type, it, start, nxt)\
+{ \
+	type it = start; \
+	while (it) { \
+		type next_##it = it->nxt;
+
+/**
+ * lws_end_foreach_ll_safe(): linkedlist iterator helper end (pre increment storage)
+ *
+ * \param it: same iterator var name given when starting
+ *
+ * This helper is the partner for lws_start_foreach_ll_safe() that ends the
+ * while loop. It uses the precreated next_ variable already stored during
+ * start.
+ */
+
+#define lws_end_foreach_ll_safe(it) \
+		it = next_##it; \
+	} \
+}
+
 /**
  * lws_start_foreach_llp(): linkedlist pointer iterator helper start
  *