From 74ee7ee091958683725aa1bc9ef0cb027b49718b Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Fri, 3 Jun 2022 04:56:28 +0200
Subject: [PATCH] Add parallel realtime threads to CoreAudio workgroup

This API is only available since BigSur (11.0), see also
https://developer.apple.com/documentation/audiotoolbox/workgroup_management/adding_parallel_real-time_threads_to_audio_workgroups?language=objc
---
 libs/backends/coreaudio/coreaudio_backend.cc | 41 +++++++++++++++++++-
 libs/backends/coreaudio/coreaudio_backend.h  |  6 +++
 libs/backends/coreaudio/coreaudio_pcmio.cc   |  9 +++++
 libs/backends/coreaudio/coreaudio_pcmio.h    |  8 ++++
 4 files changed, 63 insertions(+), 1 deletion(-)

diff --git a/libs/backends/coreaudio/coreaudio_backend.cc b/libs/backends/coreaudio/coreaudio_backend.cc
index 78d1730d3d..72ec0d277d 100644
--- a/libs/backends/coreaudio/coreaudio_backend.cc
+++ b/libs/backends/coreaudio/coreaudio_backend.cc
@@ -830,9 +830,40 @@ void *
 CoreAudioBackend::coreaudio_process_thread (void *arg)
 {
 	ThreadData* td = reinterpret_cast<ThreadData*> (arg);
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 110000
+	if (td->_joined_workgroup) {
+		/* have WG */
+		int res = os_workgroup_join (td->_workgroup, &td->_join_token);
+		switch (res) {
+			case 0:
+				PBD::info << _("AudioEngine: process thread joined AUHAL workgroup.") << endmsg;
+				break;
+			case EALREADY:
+				PBD::warning << _("AudioEngine: process thread is already in a workgroup.") << endmsg;
+				td->_joined_workgroup = false;
+				break;
+			case EINVAL:
+				PBD::warning << _("AudioEngine: invalid workgroup for process thread.") << endmsg;
+				td->_joined_workgroup = false;
+				break;
+			default:
+				td->_joined_workgroup = false;
+				PBD::warning << _("AudioEngine: process thread failed to join AUHAL workgroup.") << endmsg;
+				break;
+
+		}
+	}
+#endif
+
 	boost::function<void ()> f = td->f;
-	delete td;
 	f ();
+
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 110000
+	if (td->_joined_workgroup) {
+		os_workgroup_leave (td->_workgroup, &td->_join_token);
+	}
+#endif
+	delete td;
 	return 0;
 }
 
@@ -842,6 +873,14 @@ CoreAudioBackend::create_process_thread (boost::function<void()> func)
 	pthread_t   thread_id;
 	ThreadData* td = new ThreadData (this, func, PBD_RT_STACKSIZE_PROC);
 
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 110000
+	if (_pcmio->workgroup (td->_workgroup)) {
+		td->_joined_workgroup = true;
+	} else {
+		td->_joined_workgroup = false;
+	}
+#endif
+
 	if (pbd_realtime_pthread_create (PBD_SCHED_FIFO, PBD_RT_PRI_PROC, PBD_RT_STACKSIZE_PROC,
 	                              &thread_id, coreaudio_process_thread, td)) {
 		if (pbd_pthread_create (PBD_RT_STACKSIZE_PROC, &thread_id, coreaudio_process_thread, td)) {
diff --git a/libs/backends/coreaudio/coreaudio_backend.h b/libs/backends/coreaudio/coreaudio_backend.h
index b3839f68a2..34c17590b8 100644
--- a/libs/backends/coreaudio/coreaudio_backend.h
+++ b/libs/backends/coreaudio/coreaudio_backend.h
@@ -389,6 +389,12 @@ class CoreAudioBackend : public AudioBackend, public PortEngineSharedImpl {
 		boost::function<void ()> f;
 		size_t stacksize;
 
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 110000
+		bool                      _joined_workgroup;
+		os_workgroup_t            _workgroup;
+		os_workgroup_join_token_s _join_token;
+#endif
+
 		ThreadData (CoreAudioBackend* e, boost::function<void ()> fp, size_t stacksz)
 			: engine (e) , f (fp) , stacksize (stacksz) {}
 	};
diff --git a/libs/backends/coreaudio/coreaudio_pcmio.cc b/libs/backends/coreaudio/coreaudio_pcmio.cc
index 3619064f64..a38a3f5afd 100644
--- a/libs/backends/coreaudio/coreaudio_pcmio.cc
+++ b/libs/backends/coreaudio/coreaudio_pcmio.cc
@@ -1209,6 +1209,15 @@ CoreAudioPCM::set_playback_channel (uint32_t chn, const float *output, uint32_t
 	return 0;
 }
 
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 110000
+bool
+CoreAudioPCM::workgroup (os_workgroup_t& workgroup)
+{
+	assert (_auhal);
+	UInt32 size = sizeof (os_workgroup_t);
+	return noErr == AudioUnitGetProperty (_auhal, kAudioOutputUnitProperty_OSWorkgroup, kAudioUnitScope_Output, 0, &workgroup, &size);
+}
+#endif
 
 void
 CoreAudioPCM::launch_control_app (uint32_t device_id)
diff --git a/libs/backends/coreaudio/coreaudio_pcmio.h b/libs/backends/coreaudio/coreaudio_pcmio.h
index e53cf29670..765b42ddc9 100644
--- a/libs/backends/coreaudio/coreaudio_pcmio.h
+++ b/libs/backends/coreaudio/coreaudio_pcmio.h
@@ -23,6 +23,10 @@
 #include <CoreAudio/CoreAudio.h>
 #include <AudioUnit/AudioUnit.h>
 
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 110000
+# include <AudioToolbox/AudioToolbox.h>
+#endif
+
 #include <AudioUnit/AudioUnit.h>
 #include <AudioToolbox/AudioToolbox.h>
 
@@ -74,6 +78,10 @@ public:
 
 	void     launch_control_app (uint32_t device_id);
 
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= 110000
+	bool workgroup (os_workgroup_t&);
+#endif
+
 	void     pcm_stop (void);
 	int      pcm_start (
 			uint32_t input_device,