static void bus_reset_queues(sd_bus *b) {
assert(b);
+ /* NOTE: We _must_ decrement b->Xqueue_size before calling
+ * sd_bus_message_unref() for _each_ message. Otherwise the
+ * self-reference checks in sd_bus_unref() will fire for each message.
+ * We would thus recurse into sd_bus_message_unref() and trigger the
+ * assert(m->n_ref > 0) */
+
while (b->rqueue_size > 0)
sd_bus_message_unref(b->rqueue[--b->rqueue_size]);
if (!bus)
return NULL;
+ /* TODO/FIXME: It's naive to think REFCNT_GET() is thread-safe in any
+ * way but exclusive REFCNT_DEC(). The current logic _must_ lock around
+ * REFCNT_GET() until REFCNT_DEC() or two threads might end up in
+ * parallel in bus_reset_queues(). But locking would totally break the
+ * recursion we introduce by bus_reset_queues()...
+ * (Imagine one thread in sd_bus_message_unref() setting n_ref to 0 and
+ * thus calling into sd_bus_unref(). If at the same time the real
+ * thread calls sd_bus_unref(), both end up with "q == true" and will
+ * call into bus_reset_queues().
+ * If we require the main bus to be alive until all dispatch threads
+ * are done, there is no need to do ref-counts at all. So in both ways,
+ * the REFCNT thing is humbug.)
+ *
+ * On a second note: messages are *not* required to have ->bus set nor
+ * does it have to be _this_ bus that they're assigned to. This whole
+ * ref-cnt checking breaks apart if a message is not assigned to us.
+ * (which is _very_ easy to trigger with the current API). */
+
if (REFCNT_GET(bus->n_ref) == bus->rqueue_size + bus->wqueue_size + 1) {
bool q = true;
/* We are the only holders on the messages, and the
* messages are the only holders on us, so let's drop
* the messages and thus implicitly also kill our own
- * last references */
+ * last references.
+ * bus_reset_queues() decrements the queue-size before
+ * calling into sd_bus_message_unref(). Thus, it
+ * protects us from recursion. */
if (q)
bus_reset_queues(bus);
bus->event_priority = priority;
- r = sd_event_add_monotonic(bus->event, &bus->time_event_source, 0, 0, time_callback, bus);
+ r = sd_event_add_time(bus->event, &bus->time_event_source, CLOCK_MONOTONIC, 0, 0, time_callback, bus);
if (r < 0)
goto fail;
bus->quit_event_source = sd_event_source_unref(bus->quit_event_source);
}
- if (bus->event)
- bus->event = sd_event_unref(bus->event);
-
+ bus->event = sd_event_unref(bus->event);
return 1;
}
assert_return(ret, -EINVAL);
assert_return(!bus_pid_changed(bus), -ECHILD);
- if (!bus->is_kernel)
+ if (bus->is_kernel)
return -ENOTSUP;
if (!BUS_IS_OPEN(bus->state))