fix deadlock and freeze

src/main/java/de/bixilon/minosoft/data/world/chunk/light/SectionLight.kt

@@ -226,7 +226,7 @@ class SectionLight(
         update = true
         val blocks = section.blocks
 
-        blocks.lock?.acquire()
+        section.chunk.lock.lock()
         val min = blocks.minPosition
         val max = blocks.maxPosition
 
@@ -243,7 +243,7 @@ class SectionLight(
                 }
             }
         }
-        blocks.lock?.release()
+        section.chunk.lock.unlock()
         section.chunk.light.sky.recalculate(section.sectionHeight)
     }
 

src/main/java/de/bixilon/minosoft/util/DebugLock.kt

@@ -0,0 +1,68 @@
+/*
+ * Minosoft
+ * Copyright (C) 2020-2023 Moritz Zwerger
+ *
+ * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with this program. If not, see <https://www.gnu.org/licenses/>.
+ *
+ * This software is not affiliated with Mojang AB, the original developer of Minecraft.
+ */
+
+package de.bixilon.minosoft.util
+
+import de.bixilon.kutil.concurrent.lock.Lock
+import de.bixilon.kutil.concurrent.lock.NobodyIsReadingException
+import de.bixilon.kutil.concurrent.lock.NobodyIsWritingException
+
+
+@Deprecated("kutil 1.25")
+class DebugLock : Lock {
+    private val lock = Object()
+    override var readers = 0
+        private set
+    override var locked = false
+        private set
+
+    override fun acquire() {
+        synchronized(lock) {
+            while (locked) {
+                lock.wait()
+            }
+            readers++
+            //    Exception("acquire").printStackTrace()
+            lock.notifyAll()
+        }
+    }
+
+    override fun release() {
+        synchronized(lock) {
+            if (readers <= 0) throw NobodyIsReadingException()
+            readers--
+            //     Exception("release").printStackTrace()
+            lock.notifyAll()
+        }
+    }
+
+    override fun lock() {
+        synchronized(lock) {
+            while (locked || readers > 0) {
+                lock.wait()
+            }
+            locked = true
+            Exception("lock").printStackTrace()
+            lock.notifyAll()
+        }
+    }
+
+    override fun unlock() {
+        synchronized(lock) {
+            if (!locked) throw NobodyIsWritingException()
+            locked = false
+            Exception("unlock").printStackTrace()
+            lock.notifyAll()
+        }
+    }
+}