Fix the infinite cycle in Lazy Vlas

DarkDimius · web-flow · commit d799a9162da0 · 2017-04-19T11:07:47.000-05:00
Reported by Andrzej Plutecki in https://groups.google.com/forum/#!topic/dotty-internals/3LMNItLQw-A I haven't seen this happen in practice in hours and hours of benchmarking, but this is indeed a formal bug.
diff --git a/library/src/dotty/runtime/LazyVals.scala b/library/src/dotty/runtime/LazyVals.scala
@@ -55,7 +55,8 @@ object LazyVals {
       else if (state == 2) {
         val monitor = getMonitor(t, ord)
         monitor.synchronized {
-          monitor.wait()
+          if (STATE(cur, ord) == 2)
+            monitor.wait()
         }
       }
       else retry = false

Original file line number	Diff line number	Diff line change
`@@ -55,7 +55,8 @@ object LazyVals {`
`55`	`55`	`else if (state == 2) {`
`56`	`56`	`val monitor = getMonitor(t, ord)`
`57`	`57`	`monitor.synchronized {`
`58`		`- monitor.wait()`
	`58`	`+ if (STATE(cur, ord) == 2)`
	`59`	`+ monitor.wait()`
`59`	`60`	`}`
`60`	`61`	`}`
`61`	`62`	`else retry = false`