diff options
Diffstat (limited to 'src/shared/varlink.c')
| -rw-r--r-- | src/shared/varlink.c | 33 |
1 files changed, 25 insertions, 8 deletions
diff --git a/src/shared/varlink.c b/src/shared/varlink.c index 31128e02e0..6ed72075ba 100644 --- a/src/shared/varlink.c +++ b/src/shared/varlink.c @@ -1206,8 +1206,9 @@ int varlink_close(Varlink *v) { varlink_set_state(v, VARLINK_DISCONNECTED); - /* Let's take a reference first, since varlink_detach_server() might drop the final (dangling) ref - * which would destroy us before we can call varlink_clear() */ + /* Let's take a reference first, since varlink_detach_server() might drop the final ref from the + * disconnect callback, which would invalidate the pointer we are holding before we can call + * varlink_clear(). */ varlink_ref(v); varlink_detach_server(v); varlink_clear(v); @@ -1220,17 +1221,33 @@ Varlink* varlink_close_unref(Varlink *v) { if (!v) return NULL; - (void) varlink_close(v); + /* A reference is given to us to be destroyed. But when calling varlink_close(), a callback might + * also drop a reference. We allow this, and will hold a temporary reference to the object to make + * sure that the object still exists when control returns to us. If there's just one reference + * remaining after varlink_close(), even though there were at least two right before, we'll handle + * that gracefully instead of crashing. + * + * In other words, this call drops the donated reference, but if the internal call to varlink_close() + * dropped a reference to, we don't drop the reference afain. This allows the caller to say: + * global_object->varlink = varlink_close_unref(global_object->varlink); + * even though there is some callback which has access to global_object and may drop the reference + * stored in global_object->varlink. Without this step, the same code would have to be written as: + * Varlink *t = TAKE_PTR(global_object->varlink); + * varlink_close_unref(t); + */ + /* n_ref >= 1 */ + varlink_ref(v); /* n_ref >= 2 */ + varlink_close(v); /* n_ref >= 1 */ + if (v->n_ref > 1) + v->n_ref--; /* n_ref >= 1 */ return varlink_unref(v); } Varlink* varlink_flush_close_unref(Varlink *v) { - if (!v) - return NULL; + if (v) + varlink_flush(v); - (void) varlink_flush(v); - (void) varlink_close(v); - return varlink_unref(v); + return varlink_close_unref(v); } static int varlink_enqueue_json(Varlink *v, JsonVariant *m) { |