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From e02e290d7cccd0cfbc89bacf5c0be7934ee58ece Mon Sep 17 00:00:00 2001
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From: Tanu Kaskinen <tanuk@iki.fi>
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Date: Wed, 16 Jan 2013 03:36:03 +0200
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Subject: [PATCH 4/7] Call change_cb() only when there's an actual change.
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Calling change_cb() whenever anything happens in the ownership of the
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bus name caused trouble in PulseAudio in this scenario:
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1. PulseAudio is using a device and owns the corresponding service
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name.
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2. Another application requests device release.
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3. PulseAudio releases the device.
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4. Change in the bus name ownership: PulseAudio gives up the
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ownership, and nobody owns the name.
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5. reserve-monitor notices that, and notifies PulseAudio.
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6. Since reserve-monitor reports the device as "not busy", PulseAudio
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decides to reserve the bus name immediately back to itself and
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opens the device again.
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The other application will forcibly take the bus name to itself, as
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it should according to the protocol, but the other application may
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have trouble opening the device if it tries to do that before
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PulseAudio has had time to react to the NameLost signal.
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This can be solved by not calling change_cb() if there are no changes
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in the device busy status. In this scenario the device is considered
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"not busy" while PulseAudio is owning the bus name, so PulseAudio gets
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no notification when the ownership changes from PulseAudio to nobody.
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---
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src/modules/reserve-monitor.c | 4 +++-
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1 file changed, 3 insertions(+), 1 deletion(-)
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diff --git a/src/modules/reserve-monitor.c b/src/modules/reserve-monitor.c
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index ab453e6..4097a6f 100644
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--- a/src/modules/reserve-monitor.c
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+++ b/src/modules/reserve-monitor.c
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@@ -85,6 +85,8 @@ static DBusHandlerResult filter_handler(
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goto invalid;
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if (strcmp(name, m->service_name) == 0) {
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+ unsigned old_busy = m->busy;
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+
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m->busy = !!(new && *new);
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/* If we ourselves own the device, then don't consider this 'busy' */
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@@ -96,7 +98,7 @@ static DBusHandlerResult filter_handler(
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m->busy = FALSE;
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}
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- if (m->change_cb) {
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+ if (m->busy != old_busy && m->change_cb) {
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m->ref++;
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m->change_cb(m);
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rm_release(m);
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--
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1.8.1.4
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