Merge pull request #728 from Safety0ff/fix11454

Fix issue 11519 - race in core.thread unit test

Author: MartinNowak

src/core/thread.d

@@ -2668,21 +2668,26 @@ unittest
     import core.sync.semaphore;
 
     shared bool inCriticalRegion;
-    auto sem = new Semaphore();
+    auto sema = new Semaphore(),
+         semb = new Semaphore();
 
     auto thr = new Thread(
     {
         thread_enterCriticalRegion();
         inCriticalRegion = true;
-        sem.notify();
+        sema.notify();
+        semb.wait();
+
         Thread.sleep(dur!"msecs"(1));
         inCriticalRegion = false;
         thread_exitCriticalRegion();
     });
     thr.start();
 
-    sem.wait();
+    sema.wait();
     assert(inCriticalRegion);
+    semb.notify();
+
     thread_suspendAll();
     assert(!inCriticalRegion);
     thread_resumeAll();