Index: compiler-rt/trunk/lib/tsan/CMakeLists.txt
===================================================================
--- compiler-rt/trunk/lib/tsan/CMakeLists.txt
+++ compiler-rt/trunk/lib/tsan/CMakeLists.txt
@@ -118,7 +118,7 @@
                 RTUbsan
     CFLAGS ${TSAN_RTL_CFLAGS}
     LINK_FLAGS ${SANITIZER_COMMON_LINK_FLAGS} ${WEAK_SYMBOL_LINK_FLAGS}
-    LINK_LIBS ${TSAN_LINK_LIBS}
+    LINK_LIBS ${TSAN_LINK_LIBS} objc
     PARENT_TARGET tsan)
   add_compiler_rt_object_libraries(RTTsan_dynamic
     OS ${TSAN_SUPPORTED_OS}
Index: compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors_mac.cc
===================================================================
--- compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors_mac.cc
+++ compiler-rt/trunk/lib/tsan/rtl/tsan_interceptors_mac.cc
@@ -294,6 +294,19 @@
 
 #endif  // #if defined(__has_include) && __has_include(<xpc/xpc.h>)
 
+TSAN_INTERCEPTOR(int, objc_sync_enter, void *obj) {
+  SCOPED_TSAN_INTERCEPTOR(objc_sync_enter, obj);
+  int result = REAL(objc_sync_enter)(obj);
+  if (obj) Acquire(thr, pc, (uptr)obj);
+  return result;
+}
+
+TSAN_INTERCEPTOR(int, objc_sync_exit, void *obj) {
+  SCOPED_TSAN_INTERCEPTOR(objc_sync_enter, obj);
+  if (obj) Release(thr, pc, (uptr)obj);
+  return REAL(objc_sync_exit)(obj);
+}
+
 // On macOS, libc++ is always linked dynamically, so intercepting works the
 // usual way.
 #define STDCXX_INTERCEPTOR TSAN_INTERCEPTOR
Index: compiler-rt/trunk/test/tsan/Darwin/objc-synchronize.mm
===================================================================
--- compiler-rt/trunk/test/tsan/Darwin/objc-synchronize.mm
+++ compiler-rt/trunk/test/tsan/Darwin/objc-synchronize.mm
@@ -0,0 +1,57 @@
+// RUN: %clangxx_tsan %s -o %t -framework Foundation -fobjc-arc %darwin_min_target_with_full_runtime_arc_support
+// RUN: %run %t 2>&1 | FileCheck %s
+
+#import <Foundation/Foundation.h>
+
+@interface MyClass : NSObject {
+  long field;
+}
+@property (nonatomic, readonly) long value;
+@end
+
+dispatch_group_t group;
+
+@implementation MyClass
+
+- (void) start {
+  dispatch_queue_t q = dispatch_queue_create(NULL, NULL);
+  dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+    for (int i = 0; i < 1000; i++) {
+      dispatch_async(q, ^{
+        @synchronized(self) {
+          self->field = i;
+        }
+      });
+    }
+  });
+}
+
+- (long) value {
+  @synchronized(self) {
+    return self->field;
+  }
+}
+
+- (void)dealloc {
+  dispatch_group_leave(group);
+}
+
+@end
+
+int main() {
+  group = dispatch_group_create();
+  @autoreleasepool {
+    for (int j = 0; j < 100; ++j) {
+      dispatch_group_enter(group);
+      MyClass *obj = [[MyClass alloc] init];
+      [obj start];
+      long x = obj.value;
+      (void)x;
+    }
+  }
+  dispatch_group_wait(group, DISPATCH_TIME_FOREVER);
+  NSLog(@"Hello world");
+}
+
+// CHECK: Hello world
+// CHECK-NOT: WARNING: ThreadSanitizer