From cce1a67e75e9e4031edd70f433f295089deb0010 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Tue, 30 Mar 2021 01:28:44 +0200
Subject: [PATCH] zita-convolver: fix hang at when re-loading state

The convolver may be re-activated shortly after initialization
(e.g. session load, switching snapshots, or buffer-size.

In this case not all process threads may have started.
Convproc::stop_process() skips them (their state is still ST_IDLE).
Yet some short time later the thread's main function runs
and changes the state to ST_PROC, and check_stop () waits forever.

This is solved by waiting for all threads to start.
---
 libs/zita-convolver/zita-convolver.cc         | 26 +++++++++++++++----
 .../zita-convolver/zita-convolver.h           |  1 +
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/libs/zita-convolver/zita-convolver.cc b/libs/zita-convolver/zita-convolver.cc
index 96a00c05d5..3b2473b854 100644
--- a/libs/zita-convolver/zita-convolver.cc
+++ b/libs/zita-convolver/zita-convolver.cc
@@ -265,6 +265,16 @@ Convproc::start_process (int abspri, int policy)
 	for (k = (_minpart == _quantum) ? 1 : 0; k < _nlevels; k++) {
 		_convlev[k]->start (abspri, policy);
 	}
+
+	while (!check_started ((_minpart == _quantum) ? 1 : 0)) {
+#ifdef _MSC_VER
+		Sleep (40);
+#else
+		usleep (40000);
+#endif
+		sched_yield ();
+	}
+
 	_state = ST_PROC;
 	return 0;
 }
@@ -352,10 +362,11 @@ Convproc::cleanup (void)
 
 	while (!check_stop ()) {
 #ifdef _MSC_VER
-		Sleep (100);
+		Sleep (40);
 #else
-		usleep (100000);
+		usleep (40000);
 #endif
+		sched_yield ();
 	}
 	for (k = 0; k < _ninp; k++) {
 		delete[] _inpbuff[k];
@@ -382,14 +393,19 @@ Convproc::cleanup (void)
 	return 0;
 }
 
+bool
+Convproc::check_started (uint32_t k)
+{
+	for (; (k < _nlevels) && (_convlev[k]->_stat == Convlevel::ST_PROC); k++) ;
+	return (k == _nlevels) ? true : false;
+}
+
 bool
 Convproc::check_stop (void)
 {
 	uint32_t k;
 
-	for (k = 0; (k < _nlevels) && (_convlev[k]->_stat == Convlevel::ST_IDLE); k++) {
-		;
-	}
+	for (k = 0; (k < _nlevels) && (_convlev[k]->_stat == Convlevel::ST_IDLE); k++) ;
 	if (k == _nlevels) {
 		_state = ST_STOP;
 		return true;
diff --git a/libs/zita-convolver/zita-convolver/zita-convolver.h b/libs/zita-convolver/zita-convolver/zita-convolver.h
index 81fa0c8321..74f8e41c5b 100644
--- a/libs/zita-convolver/zita-convolver/zita-convolver.h
+++ b/libs/zita-convolver/zita-convolver/zita-convolver.h
@@ -397,6 +397,7 @@ public:
 
 	int stop_process (void);
 
+	bool check_started (uint32_t);
 	bool check_stop (void);
 
 	int cleanup (void);