While POSIX defines a single contiguous range of numbers that
determine a thread's priority. Win32 defines priority classes
and priority levels relative to these classes.
pthread maps those to -15 .. +15 with the top six ones
corresponding to REALTIME_PRIORITY_CLASS and max being
THREAD_PRIORITY_TIME_CRITICAL
Note that the PA backend can USE_MMCSS_THREAD_PRIORITIES
and PBD::MMCSS::set_thread_characteristics() directly for
the I/O threads.
RegionFactory::CheckNewRegion signal is emitted directly
after region-creation from RegionFactory::create().
At this point in time the region is not on any playlist.
This if fine for EditorSources, but the new RegionList design
only shows regions that are on the timeline.
CheckNewRegion() -> EditorRegions::add_region()
-> EditorRegions::regions_changed() ignores regions w/o playlist.
Later Playlist::add_region_internal() sets the playlist but
calls Region::clear_changes() to not send all individual changes.
So Region::RegionsPropertyChanged is not emitted either.
We need to notify the EditorRegions *after* setting the playlist.
The downside of this is that more signals than necessary are
emitted.
If the wrong device profile is selected (ex Xtouch One) but another device
is connected (Xtouch), it is possible to have a master fader on the
device, but not in the code. This would then cause a crash when the
master fader was touched.
This just protects from a wrong configuration.
All Immediate events have the same action samples, while other
parameters differ. Those events must not be removed by a
call to _remove_event(), particularly not SessionEvent::Overwrite
After an edit option the playlist is thawed and triggers
the butler thread (SessionEvent::Overwrite) to re-read the
playlist.
If another edit operation is started the butler may reads a
region using the region's new position, but the playlist's
old range.
See also 4db1c02bd1
The previous design had a race condition. When WaveViewThreads::stop_threads() was called, it would
first acquire the mutex, then set _quit, then call condition.broadcast(). But worker threads would
check _quit without holding the mutex. It was therefore for a thread to be delayed in its
own lock acquisition by the ::stop_threads() caller, then end up back in cond.wait() AFTER
the cond.broadcast() was done. Such a thread would sleep forever and never wake up.
This new design removes WaveViewDrawRequestQueue, which was a clean encapsulation of the
queueing aspects of WaveViewThreads, but unfortunately made correct mutex acquisition
and condition signalling/waiting needlessly complex. THe mutex, condition variable
and actual queue were moved into WaveViewThreads, and all worker threads execute a method
of the class which gives the appropriate code easy access to the mutex and condition var,
which must always be used together.
This replaces a Mutex and adds additional read-locks.
This is needed to address some threading issues with rt-threads
calling auto_loop_location() while the GUI changes locations.
Since locations are C-pointers this is still not entirely safe!
Locations::remove() may delete a location while a pointer
to it is being used in another thread.
Previously the freewheel export thread directly called
Session::butler_transport_work(). The butler thread
may concurrently call the same function. This can lead
double free or memory corruption (see below)
Now export thread summons the butler and does nothing
until it completed its work.
```
Export Thread:
3 XMLNode::~XMLNode
4 ARDOUR::AutomationList::snapshot_history
5 ARDOUR::AutomationList::start_write_pass
6 ARDOUR::Automatable::non_realtime_locate
7 ARDOUR::Route::non_realtime_locate
8 ARDOUR::Session::non_realtime_locate
9 ARDOUR::Session::butler_transport_work
10 ARDOUR::Session::process_export_fw
Butler thread:
7 XMLNode::~XMLNode
8 ARDOUR::AutomationList::snapshot_history
9 ARDOUR::AutomationList::start_write_pass
10 ARDOUR::Automatable::non_realtime_locate
11 ARDOUR::Route::non_realtime_locate
12 ARDOUR::Session::non_realtime_locate
13 ARDOUR::Session::butler_transport_work
14 ARDOUR::Butler::thread_work
15 ARDOUR::Butler::_thread_work
```
