From 1db09d30138c54de64f8e197eb6d60b8a04d31c8 Mon Sep 17 00:00:00 2001 From: Mikel Astiz Date: Wed, 30 Jan 2013 09:30:31 +0100 Subject: [PATCH 7/7] reserve: Fix leaking NameLost signals after release+acquire The use of the pseudo-blocking D-Bus calls leads to the problem that NameLost signals are received after the reply to ReleaseName(). The problem with this is that a later acquisition of the same audio device can potentially receive the NameLost signal corresponding to the previous instance, due to the fact that the signal hasn't been popped from the D-Bus message queue. The simplest approach to solve this problem is to poll the actual name owner from the D-Bus daemon, in order to make sure that we did really lose the name. The proposal uses a blocking call to GetNameOwner to avoid incosistent states in the internal APIs: it would otherwise be possible to have a "busy" device before the reservation has been lost, in the unlikely case if some other process acquires the name before we got the confirmation that the NameLost was actually true. --- src/modules/reserve.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/src/modules/reserve.c b/src/modules/reserve.c index bbb6773..f78805e 100644 --- a/src/modules/reserve.c +++ b/src/modules/reserve.c @@ -293,6 +293,7 @@ static DBusHandlerResult filter_handler( rd_device *d; DBusError error; + char *name_owner = NULL; dbus_error_init(&error); @@ -310,6 +311,21 @@ static DBusHandlerResult filter_handler( goto invalid; if (strcmp(name, d->service_name) == 0 && d->owning) { + /* Verify the actual owner of the name to avoid leaked NameLost + * signals from previous reservations. The D-Bus daemon will send + * all messages asynchronously in the correct order, but we could + * potentially process them too late due to the pseudo-blocking + * call mechanism used during both acquisition and release. This + * can happen if we release the device and immediately after + * reacquire it before NameLost is processed. */ + if (!d->gave_up) { + const char *un; + + if ((un = dbus_bus_get_unique_name(c)) && rd_dbus_get_name_owner(c, d->service_name, &name_owner, &error) == 0) + if (strcmp(name_owner, un) == 0) + goto invalid; /* Name still owned by us */ + } + d->owning = 0; if (!d->gave_up) { @@ -326,6 +342,7 @@ static DBusHandlerResult filter_handler( } invalid: + free(name_owner); dbus_error_free(&error); return DBUS_HANDLER_RESULT_NOT_YET_HANDLED; -- 1.8.1.4