pulseaudio: pacat-simple-vchan startup and termination

[marmarek]

There are two issues affecting starting of pacat-simple-vchan:

1. There is no pid file - this makes qvm-start-daemon (Support for AudioVM qubes-core-admin-client#118) starting multiple instances of pacat-simple-vchan (if for example it needs to reconnect to qubesd)
2. pacat-simple-vchan may not notice VM kill (as opposed to a clean shutdown). This is because vchan may not fire an event in such a case. Other vchan applications workarounds this by periodic check if the domain is alive, but not pacat-simple-vchan.

[marmarek]

2. Other vchan applications workarounds this by periodic check if the domain is alive, but not pacat-simple-vchan.

Actually, it looks like the code for this was there before, but was removed in QubesOS/qubes-gui-daemon@d0fcc6ce

BTW (not necessary now) @pwmarcz something that vchan could do better. The issue is that event channels in Xen do not send notification when the other end (VM) dies. libxenvchan uses a Linux kernel feature to send the event when userspace process sharing memory dies (xengntshr_share_page_notify()). But when the VM is killed/crashes, Linux doesn't have a chance to send this notification. In many places we check periodically if the other end is still alive (custom code in libvchan_is_open()) - that's why various places use (p)select() with a relatively small timeout. The "official" way for getting notification about VM destruction is registering @releaseDomain xenstore watch (caveat: you don't get info which domain has been destroyed). I definitely don't want to introduce xenstore API to all kind of applications, but this is something that libvchan-xen could handle.

[qubesos-bot]

Automated announcement from builder-github

The package qubes-audio-daemon-4.1.5-1.fc31 has been pushed to the r4.1 testing repository for dom0.
To test this update, please install it with the following command:

sudo qubes-dom0-update --enablerepo=qubes-dom0-current-testing

Changes included in this update

[qubesos-bot]

Automated announcement from builder-github

The package qubes-gui-daemon_4.1.5-1 has been pushed to the r4.1 testing repository for the Debian template.
To test this update, first enable the testing repository in /etc/apt/sources.list.d/qubes-*.list by uncommenting the line containing stretch-testing (or appropriate equivalent for your template version), then use the standard update command:

sudo apt-get update && sudo apt-get dist-upgrade

Changes included in this update

[qubesos-bot]

Automated announcement from builder-github

The package qubes-gui-dom0-4.0.11-1.fc25 has been pushed to the r4.0 testing repository for dom0.
To test this update, please install it with the following command:

sudo qubes-dom0-update --enablerepo=qubes-dom0-current-testing

Changes included in this update

[qubesos-bot]

Automated announcement from builder-github

The package qubes-gui-dom0-4.0.11-1.fc25 has been pushed to the r4.0 stable repository for dom0.
To install this update, please use the standard update command:

sudo qubes-dom0-update

Or update dom0 via Qubes Manager.

Changes included in this update