`set_input/output_channels` API to limit a device to the first
`N` chnanels is somewhat ill conveived and was never really
used or useful. LiveTrax has a bitset of exposed channels,
which makes a lot more sense (e.g. hide ADAT or S/Pdif, or
some specific channels)
Ardour::cleanup destroys the TransportMasterManager instance
which unregisters TransportMaster ports. This will crash
if the engine was already destroyed.
See also 7c7bf6c88b
The old code assumed that the thread that created a request buffer for a given
signal-emitting thread would be the latter thread, and thus a thread-local
pointer to the request buffer could be used. This turns out not to be true: the
GUI thread tends to be responsible for constructing the request buffers for
pre-registered threads.
That mechanism has been replaced by using a RWLock protected map using
pthread_t as the key and the request buffer as the value. This allows any
thread to create and register the request buffers used between any other pair
of threads (because the lookup always uses a pthread_t).
The symptoms of this problem were a signal emitted in an audioengine thread
that was propagated to the target thread, but when the target thread scans its
request buffers for requests, it finds nothing (because it didn't know about
the request buffer). In a sense, the signal was successfully delivered to the
target thread, but no meaningful work (i.e the signal handler) is performed.
It can happen that ::get_request() returns NULL if the
EventPool is full. In that case the slot is never called.
In this case the caller can now take action.
Some overzealous locking to track down RequestObject related crashes.
bc0fa4d689 wrongly locked the current event loop's
request_invalidation_lock instead of the invalidation's list lock.
Also Abstract UI is able to delete requests concurrently with with
EventLoop invalidation.
e.g. PortManager::PortRegisteredOrUnregistered and GlobalPortMatrixWindow
so the lock needs to be exposed.
If this solves various issues, mutexes should to be consolidated
(request_buffer_map_lock + request_invalidation_lock) and be chosen
such that there is as little contention as possible.
