On Windows (and OSX) semaphores are named. If the name matches an existing
semaphore, it is re-used and not re-initialized. In case of multiple
LV2-plugins each with a worker-thread this can lead to a deadlock.
The original LV2 state extension required that run() is suspended during
restore(). Ardour violates this rule, which can lead to crashes and
other issues.
The state extension has been updated to allow restoring state in a
thread-safe way by using the worker to enqueue state changes. This
commit supports that new specification, i.e. supports dropout-free state
restoration properly.
However, the bug with old plugins that do not use this facility is still
not fixed.
start worker thread after _sem and _exit have been initialized.
stop thread when plugin is removed.
git-svn-id: svn://localhost/ardour2/branches/3.0@13145 d708f5d6-7413-0410-9779-e7cbd77b26cf
This is done by way of a generic Worker object/thread, which currently just
applies to one LV2 plugin, but the idea is to share one thread and set of
buffers among many plugins. The same pattern may also be useful elsewhere in
Ardour. The responding part gets a bit tricker when sharing a worker between
plugins, it's not a blocker, and I'm lazy, sooo here's this.
This commit also adds a new portable in-process semaphore to PBD. The existing
one is pretty weird and uses a named semaphore on OSX for reasons unknown to
me. Perhaps as a quick fix to avoid POSIX semaphores being utterly broken on
OSX? It would probably be a good idea to replace that with this new one, which
uses Mach kernel semaphores on OSX which work well, though I am not sure how
pedantically real-time safe they are to signal.
git-svn-id: svn://localhost/ardour2/branches/3.0@11790 d708f5d6-7413-0410-9779-e7cbd77b26cf
Robin Gareus
David Robillard
John Emmas
Paul Davis