From 00da2ee53e0da3a861c5a5c7ed1eaa516af2975d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Florian=20N=C3=BCcke?= <florian@nuecke.de>
Date: Sat, 25 Jul 2015 14:53:57 +0200
Subject: [PATCH] Should fix potential deadlock when machines get disposed
 while they're running. Closes #1322.

---
 .../scala/li/cil/oc/server/machine/Machine.scala     | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/main/scala/li/cil/oc/server/machine/Machine.scala b/src/main/scala/li/cil/oc/server/machine/Machine.scala
index 8bb64559b..459b7eb60 100644
--- a/src/main/scala/li/cil/oc/server/machine/Machine.scala
+++ b/src/main/scala/li/cil/oc/server/machine/Machine.scala
@@ -835,9 +835,11 @@ class Machine(val host: MachineHost) extends prefab.ManagedEnvironment with mach
       true
     }
 
-  private def close() = state.synchronized(
-    if (state.isEmpty || state.top != Machine.State.Stopped) {
-      this.synchronized {
+  private def close() =
+    if (state.synchronized(state.isEmpty || state.top != Machine.State.Stopped)) {
+      // Give up the state lock, then get the more generic lock on this instance first
+      // before locking on state again. Always must be in that order to avoid deadlocks.
+      this.synchronized(state.synchronized {
         state.clear()
         state.push(Machine.State.Stopped)
         Option(architecture).foreach(_.close())
@@ -846,11 +848,11 @@ class Machine(val host: MachineHost) extends prefab.ManagedEnvironment with mach
         cpuTotal = 0
         cpuStart = 0
         remainIdle = 0
-      }
+      })
 
       // Mark state change in owner, to send it to clients.
       host.markChanged()
-    })
+    }
 
   // ----------------------------------------------------------------------- //