From 100afadd5c6a10725ccb96386fc6fec7ce6b6763 Mon Sep 17 00:00:00 2001
From: DBotThePony <dbotthepony@yandex.ru>
Date: Fri, 19 Apr 2024 11:27:55 +0700
Subject: [PATCH] Blockable event loop without locking

---
 .../kstarbound/util/BlockableEventLoop.kt       | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/src/main/kotlin/ru/dbotthepony/kstarbound/util/BlockableEventLoop.kt b/src/main/kotlin/ru/dbotthepony/kstarbound/util/BlockableEventLoop.kt
index 8315d9a2..bb2d8e96 100644
--- a/src/main/kotlin/ru/dbotthepony/kstarbound/util/BlockableEventLoop.kt
+++ b/src/main/kotlin/ru/dbotthepony/kstarbound/util/BlockableEventLoop.kt
@@ -9,6 +9,7 @@ import org.apache.logging.log4j.LogManager
 import java.util.PriorityQueue
 import java.util.concurrent.Callable
 import java.util.concurrent.CompletableFuture
+import java.util.concurrent.ConcurrentLinkedQueue
 import java.util.concurrent.Delayed
 import java.util.concurrent.Future
 import java.util.concurrent.FutureTask
@@ -81,13 +82,13 @@ open class BlockableEventLoop(name: String) : Thread(name), ScheduledExecutorSer
 
 	private class TaskPair<T>(val future: CompletableFuture<T>, var supplier: Callable<T>?)
 
-	private val eventQueue = LinkedBlockingQueue<TaskPair<*>>()
+	private val eventQueue = ConcurrentLinkedQueue<TaskPair<*>>()
 	private val scheduledQueue = PriorityQueue<ScheduledTask<*>>()
 	val coroutines = asCoroutineDispatcher()
 	val scope = CoroutineScope(coroutines + SupervisorJob())
 
 	private fun nextDeadline(): Long {
-		if (isShutdown)
+		if (isShutdown || eventQueue.isNotEmpty())
 			return 0L
 
 		val poll = scheduledQueue.peek()
@@ -105,7 +106,7 @@ open class BlockableEventLoop(name: String) : Thread(name), ScheduledExecutorSer
 
 	private fun eventLoopIteration(): Boolean {
 		var executedAnything = false
-		val next = eventQueue.poll(nextDeadline(), TimeUnit.NANOSECONDS)
+		val next = eventQueue.poll()
 
 		if (next != null) {
 			executedAnything = true
@@ -152,6 +153,7 @@ open class BlockableEventLoop(name: String) : Thread(name), ScheduledExecutorSer
 
 	final override fun run() {
 		while (isRunning) {
+			LockSupport.parkNanos(nextDeadline())
 			eventLoopIteration()
 
 			if (isShutdown && isRunning) {
@@ -180,6 +182,7 @@ open class BlockableEventLoop(name: String) : Thread(name), ScheduledExecutorSer
 			}
 
 			eventQueue.add(pair)
+			LockSupport.unpark(this)
 		}
 	}
 
@@ -203,6 +206,7 @@ open class BlockableEventLoop(name: String) : Thread(name), ScheduledExecutorSer
 			}
 
 			eventQueue.add(pair)
+			LockSupport.unpark(this)
 			return future
 		}
 	}
@@ -240,6 +244,7 @@ open class BlockableEventLoop(name: String) : Thread(name), ScheduledExecutorSer
 			}
 
 			eventQueue.add(pair)
+			LockSupport.unpark(this)
 			return future
 		}
 	}
@@ -265,6 +270,7 @@ open class BlockableEventLoop(name: String) : Thread(name), ScheduledExecutorSer
 			}
 
 			eventQueue.add(pair)
+			LockSupport.unpark(this)
 			return future
 		}
 	}
@@ -321,7 +327,7 @@ open class BlockableEventLoop(name: String) : Thread(name), ScheduledExecutorSer
 				performShutdown()
 			} else {
 				// wake up thread
-				eventQueue.add(TaskPair(CompletableFuture()) { })
+				LockSupport.unpark(this)
 			}
 		}
 	}
@@ -359,7 +365,8 @@ open class BlockableEventLoop(name: String) : Thread(name), ScheduledExecutorSer
 				scope.cancel(CancellationException("EventLoop shut down"))
 				performShutdown()
 			} else {
-				eventQueue.add(TaskPair(CompletableFuture()) { })
+				// wake up thread
+				LockSupport.unpark(this)
 			}
 		}