On 01/29/2013 06:04 PM, Mikel Astiz wrote:
From: Mikel Astiz <[email protected]>
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. */
What do you think of this text?
/* Since signals are delivered asynchronously by the dBus daemon, we
might get the NameLost signal too late. This can happen if we release
the device and immediately after reacquire it. Therefore verify that the
name is still lost. */
+ 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)
Name_owner needs to be freed.
+ goto invalid; /* Name still
owned by us */
+ }
+
d->owning = 0;
if (!d->gave_up) {
--
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic
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