Replace control list locks with RWLocks4.0-rc4

towards fixing #6238 and #6096.


GUI thread:
#2  Glib::Threads::Mutex::Lock::Lock
#3  Evoral::ControlList::eval 
#4  Evoral::Control::get_double 
#5  ARDOUR::AutomationControl::get_value
#6  ProcessorEntry::Control::control_changed
..
#15 PBD::Timer::timeout_handler


at the same time: Audio Thread (try-lock, fails)

#0  Evoral::Curve::rt_safe_get_vector
#1  ARDOUR::Amp::setup_gain_automation
#2  ARDOUR::Route::process_output_buffers

Due to the failed try-lock.. AMP::_apply_gain_automation
is false. and Amp::run() uses a different gain factor.
-> click.

1 files changed, 2 insertions, 2 deletions

diff --git a/libs/evoral/src/Curve.cpp b/libs/evoral/src/Curve.cpp
index f99a8075d5..aed972659b 100644
--- a/libs/evoral/src/Curve.cpp
+++ b/libs/evoral/src/Curve.cpp
@@ -171,7 +171,7 @@ Curve::solve ()
 bool
 Curve::rt_safe_get_vector (double x0, double x1, float *vec, int32_t veclen)
 {
-	Glib::Threads::Mutex::Lock lm(_list.lock(), Glib::Threads::TRY_LOCK);
+	Glib::Threads::RWLock::ReaderLock lm(_list.lock(), Glib::Threads::TRY_LOCK);
 
 	if (!lm.locked()) {
 		return false;
@@ -184,7 +184,7 @@ Curve::rt_safe_get_vector (double x0, double x1, float *vec, int32_t veclen)
 void
 Curve::get_vector (double x0, double x1, float *vec, int32_t veclen)
 {
-	Glib::Threads::Mutex::Lock lm(_list.lock());
+	Glib::Threads::RWLock::ReaderLock lm(_list.lock());
 	_get_vector (x0, x1, vec, veclen);
 }