[pulseaudio-discuss] [PATCH v2 2/2] reserve: Fix leaking NameLost signals after release+acquire

Mikel Astiz mikel.astiz.oss at gmail.com
Tue Jan 29 09:04:18 PST 2013

From: Mikel Astiz <mikel.astiz at bmw-carit.de>

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 inconsistent
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 | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/modules/reserve.c b/src/modules/reserve.c
index bc2d697..6c315fe 100644
--- a/src/modules/reserve.c
+++ b/src/modules/reserve.c
@@ -310,6 +310,20 @@ static DBusHandlerResult filter_handler(
 			goto invalid;
 		if (strcmp(name, d->service_name) == 0 && d->owning) {
+			/* Request the actual owner of the name to avoid leaked
+			 * NameLost signals from previous reservations. These could
+			 * potentially remain unprocessed due to the pseudo-blocking
+			 * call mechanism used during both acquisition and
+			 * release. */
+			if (!d->gave_up) {
+				const char *un;
+				char *name_owner;
+				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)  {

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