Index: compiler-rt/trunk/lib/tsan/rtl/tsan_libdispatch_mac.cc
===================================================================
--- compiler-rt/trunk/lib/tsan/rtl/tsan_libdispatch_mac.cc
+++ compiler-rt/trunk/lib/tsan/rtl/tsan_libdispatch_mac.cc
@@ -706,6 +706,15 @@
   return REAL(dispatch_io_close)(channel, flags);
 }
 
+// Resuming a suspended queue needs to synchronize with all subsequent
+// executions of blocks in that queue.
+TSAN_INTERCEPTOR(void, dispatch_resume, dispatch_object_t o) {
+  SCOPED_TSAN_INTERCEPTOR(dispatch_resume, o);
+  Release(thr, pc, (uptr)o);  // Synchronizes with the Acquire() on serial_sync
+                              // in dispatch_sync_pre_execute
+  return REAL(dispatch_resume)(o);
+}
+
 }  // namespace __tsan
 
 #endif  // SANITIZER_MAC
Index: compiler-rt/trunk/test/tsan/Darwin/gcd-suspend.mm
===================================================================
--- compiler-rt/trunk/test/tsan/Darwin/gcd-suspend.mm
+++ compiler-rt/trunk/test/tsan/Darwin/gcd-suspend.mm
@@ -0,0 +1,45 @@
+// RUN: %clang_tsan %s -o %t -framework Foundation
+// RUN: %env_tsan_opts=ignore_interceptors_accesses=1 %run %t 2>&1 | FileCheck %s
+
+#import <Foundation/Foundation.h>
+
+long my_global = 0;
+
+int main(int argc, const char *argv[]) {
+  fprintf(stderr, "Hello world.\n");
+
+  dispatch_queue_t q1 = dispatch_queue_create("queue1", NULL);
+  dispatch_queue_t q2 = dispatch_queue_create("queue2", NULL);
+  dispatch_group_t g = dispatch_group_create();
+
+  dispatch_sync(q1, ^{
+    dispatch_suspend(q1);
+    dispatch_async(q2, ^{
+      my_global++;
+      dispatch_resume(q1);
+    });
+  });
+
+  dispatch_sync(q1, ^{
+    my_global++;
+  });
+
+  dispatch_sync(q1, ^{
+    dispatch_suspend(q1);
+    dispatch_group_enter(g);
+    dispatch_async(q1,^{ my_global++; });
+    dispatch_async(q1,^{ my_global++; });
+    dispatch_async(q1,^{ my_global++; dispatch_group_leave(g); });
+    my_global++;
+    dispatch_resume(q1);
+  });
+
+  dispatch_group_wait(g, DISPATCH_TIME_FOREVER);
+
+  fprintf(stderr, "Done.\n");
+  return 0;
+}
+
+// CHECK: Hello world.
+// CHECK-NOT: WARNING: ThreadSanitizer
+// CHECK: Done.