From 3b3bcd7b684fc432e48c20aa5317b56e87521c3b Mon Sep 17 00:00:00 2001
From: Jason Zaugg <jzaugg@gmail.com>
Date: Thu, 14 Nov 2013 20:03:20 +0100
Subject: Revert "temporarily disables run/reflection-sync-subtypes"

This reverts commit 04e2dbb29830d0e511cdfa8c132a9fad91d657ed,
by avoiding the ill-fated attempt to short-circuit the global
reflection lock.

I think we can do better performance wise, but lets at least
get something correct to start with.
---
 .../scala/reflect/runtime/SynchronizedSymbols.scala  | 11 +++++++++--
 test/disabled/run/reflection-sync-subtypes.scala     | 20 --------------------
 test/files/run/reflection-sync-subtypes.check        |  0
 test/files/run/reflection-sync-subtypes.scala        | 20 ++++++++++++++++++++
 4 files changed, 29 insertions(+), 22 deletions(-)
 delete mode 100644 test/disabled/run/reflection-sync-subtypes.scala
 create mode 100644 test/files/run/reflection-sync-subtypes.check
 create mode 100644 test/files/run/reflection-sync-subtypes.scala

diff --git a/src/reflect/scala/reflect/runtime/SynchronizedSymbols.scala b/src/reflect/scala/reflect/runtime/SynchronizedSymbols.scala
index 298d0ffebd..1a232c8de1 100644
--- a/src/reflect/scala/reflect/runtime/SynchronizedSymbols.scala
+++ b/src/reflect/scala/reflect/runtime/SynchronizedSymbols.scala
@@ -32,8 +32,15 @@ private[reflect] trait SynchronizedSymbols extends internal.Symbols { self: Symb
   trait SynchronizedSymbol extends Symbol {
 
     def gilSynchronizedIfNotInited[T](body: => T): T = {
-      if (isFullyInitialized) body
-      else gilSynchronized { body }
+      // TODO JZ desired, but prone to race conditions. We need the runtime reflection based
+      //      type completers to establish a memory barrier upon initialization. Maybe a volatile
+      //      write? We need to consult with the experts here. Until them, lock pessimistically.
+      //
+      //      `run/reflection-sync-subtypes.scala` fails about 1/50 times otherwise.
+      //
+      //      if (isFullyInitialized) body
+      //      else gilSynchronized { body }
+      gilSynchronized { body }
     }
 
     override def validTo = gilSynchronizedIfNotInited { super.validTo }
diff --git a/test/disabled/run/reflection-sync-subtypes.scala b/test/disabled/run/reflection-sync-subtypes.scala
deleted file mode 100644
index 7f75a464ac..0000000000
--- a/test/disabled/run/reflection-sync-subtypes.scala
+++ /dev/null
@@ -1,20 +0,0 @@
-import scala.reflect.runtime.universe._
-
-object Test extends App {
-  val n = 1000
-  val rng = new scala.util.Random()
-  val tasks = List(
-    () => typeOf[List[Int]] <:< typeOf[List[T] forSome { type T }],
-    () => typeOf[List[T] forSome { type T }] <:< typeOf[List[Any]],
-    () => typeOf[Map[Int, Object]] <:< typeOf[Iterable[(Int, String)]],
-    () => typeOf[Expr[Any] { val mirror: rootMirror.type }] <:< typeOf[Expr[List[List[List[Int]]]]{ val mirror: rootMirror.type }])
-  val perms = tasks.permutations.toList
-  val diceRolls = List.fill(n)(rng.nextInt(perms.length))
-  val threads = (1 to n) map (i => new Thread(s"Reflector-$i") {
-    override def run(): Unit = {
-      val result = perms(diceRolls(i - 1)).map(_())
-      assert(result.sorted == List(false, false, true, true))
-    }
-  })
-  threads foreach (_.start)
-}
\ No newline at end of file
diff --git a/test/files/run/reflection-sync-subtypes.check b/test/files/run/reflection-sync-subtypes.check
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/test/files/run/reflection-sync-subtypes.scala b/test/files/run/reflection-sync-subtypes.scala
new file mode 100644
index 0000000000..7f75a464ac
--- /dev/null
+++ b/test/files/run/reflection-sync-subtypes.scala
@@ -0,0 +1,20 @@
+import scala.reflect.runtime.universe._
+
+object Test extends App {
+  val n = 1000
+  val rng = new scala.util.Random()
+  val tasks = List(
+    () => typeOf[List[Int]] <:< typeOf[List[T] forSome { type T }],
+    () => typeOf[List[T] forSome { type T }] <:< typeOf[List[Any]],
+    () => typeOf[Map[Int, Object]] <:< typeOf[Iterable[(Int, String)]],
+    () => typeOf[Expr[Any] { val mirror: rootMirror.type }] <:< typeOf[Expr[List[List[List[Int]]]]{ val mirror: rootMirror.type }])
+  val perms = tasks.permutations.toList
+  val diceRolls = List.fill(n)(rng.nextInt(perms.length))
+  val threads = (1 to n) map (i => new Thread(s"Reflector-$i") {
+    override def run(): Unit = {
+      val result = perms(diceRolls(i - 1)).map(_())
+      assert(result.sorted == List(false, false, true, true))
+    }
+  })
+  threads foreach (_.start)
+}
\ No newline at end of file
-- 
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