[corlib] Fix a race in LazyTest.EnsureSingleThreadSafeExecution ().

1 files changed, 8 insertions, 3 deletions

diff --git a/mcs/class/corlib/Test/System/LazyTest.cs b/mcs/class/corlib/Test/System/LazyTest.cs
index ce75180cb1b..0b3e042e309 100644
--- a/mcs/class/corlib/Test/System/LazyTest.cs
+++ b/mcs/class/corlib/Test/System/LazyTest.cs
@@ -114,6 +114,7 @@ namespace MonoTests.System
 		public void EnsureSingleThreadSafeExecution ()
 		{
 			counter = 42;
+			bool started = false;
 
 			var l = new Lazy<int> (delegate () { return counter ++; }, true);
 			bool failed = false;
@@ -122,16 +123,20 @@ namespace MonoTests.System
 			for (int i = 0; i < threads.Length; ++i) {
 				threads [i] = new Thread (delegate () {
 						lock (monitor) {
-							if (!Monitor.Wait (monitor, 2000))
-								failed = true;
+							if (!started) {
+								if (!Monitor.Wait (monitor, 2000))
+									failed = true;
+							}
 						}
 						int val = l.Value;
 					});
 			}
 			for (int i = 0; i < threads.Length; ++i)
 				threads [i].Start ();
-			lock (monitor)
+			lock (monitor) {
+				started = true;
 				Monitor.PulseAll (monitor);
+			}
 
 			for (int i = 0; i < threads.Length; ++i)
 				threads [i].Join ();