Fix bug 6586:

runtime/vm/thread_test.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/assert.h"
 #include "vm/isolate.h"
 #include "vm/unit_test.h"
 #include "vm/thread.h"
 
 namespace dart {
@@ skipping 21 matching lines @@
 
 
 UNIT_TEST_CASE(Monitor) {
   // This unit test case needs a running isolate.
   Isolate* isolate = Isolate::Init(NULL);
 
   Monitor* monitor = new Monitor();
   monitor->Enter();
   monitor->Exit();
 
-  {
+  const int kNumAttempts = 5;
+  int attempts = 0;
+  while (attempts < kNumAttempts) {
     MonitorLocker ml(monitor);
     int64_t start = OS::GetCurrentTimeMillis();
     int64_t wait_time = 2017;
     Monitor::WaitResult wait_result = ml.Wait(wait_time);
     int64_t stop = OS::GetCurrentTimeMillis();
+
+    // We expect to be timing out here.
     EXPECT_EQ(Monitor::kTimedOut, wait_result);
+
+    // Check whether this attempt falls within the exptected time limits.
+    int64_t wakeup_time = stop - start;
+    OS::Print("wakeup_time: %"Pd64"\n", wakeup_time);
     const int kAcceptableTimeJitter = 20;  // Measured in milliseconds.
-    EXPECT_LE(wait_time - kAcceptableTimeJitter, stop - start);
     const int kAcceptableWakeupDelay = 150;  // Measured in milliseconds.
-    EXPECT_GE(wait_time + kAcceptableWakeupDelay, stop - start);
+    if (((wait_time - kAcceptableTimeJitter) <= wakeup_time) &&
+        (wakeup_time <= (wait_time + kAcceptableWakeupDelay))) {
+      break;
+    }
+
+    // Record the attempt.
+    attempts++;
   }
+  EXPECT_LT(attempts, kNumAttempts);
+
   // The isolate shutdown and the destruction of the mutex are out-of-order on
   // purpose.
   isolate->Shutdown();
   delete isolate;
   delete monitor;
 }
 
 }  // namespace dart