[tsan] Add support for GCD's dispatch_after and dispatch_after_f

[kubamracek]

Summary

We're missing interceptors for dispatch_after and dispatch_after_f. Let's add them to avoid false positives. Added a test case.

lib/tsan/rtl/tsan_libdispatch_mac.cc

 DISPATCH_INTERCEPT_B(dispatch_barrier_async)
 DISPATCH_INTERCEPT_F(dispatch_async_f)
 DISPATCH_INTERCEPT_F(dispatch_barrier_async_f)
 DISPATCH_INTERCEPT_SYNC_B(dispatch_sync)
 DISPATCH_INTERCEPT_SYNC_B(dispatch_barrier_sync)
 DISPATCH_INTERCEPT_SYNC_F(dispatch_sync_f)
 DISPATCH_INTERCEPT_SYNC_F(dispatch_barrier_sync_f)
 
+TSAN_INTERCEPTOR(void, dispatch_after, dispatch_time_t when,
+                 dispatch_queue_t queue, dispatch_block_t block) {
+  SCOPED_TSAN_INTERCEPTOR(dispatch_after, when, queue, block);
+  SCOPED_TSAN_INTERCEPTOR_USER_CALLBACK_START();
+  dispatch_block_t heap_block = Block_copy(block);
+  SCOPED_TSAN_INTERCEPTOR_USER_CALLBACK_END();
+  tsan_block_context_t *new_context =
+      AllocContext(thr, pc, queue, heap_block, &invoke_and_release_block);
+  Release(thr, pc, (uptr)new_context);
+  SCOPED_TSAN_INTERCEPTOR_USER_CALLBACK_START();
+  REAL(dispatch_after_f)(when, queue, new_context, dispatch_callback_wrap);
+  SCOPED_TSAN_INTERCEPTOR_USER_CALLBACK_END();
+}
+
+TSAN_INTERCEPTOR(void, dispatch_after_f, dispatch_time_t when,
+                 dispatch_queue_t queue, void *context,
+                 dispatch_function_t work) {
+  SCOPED_TSAN_INTERCEPTOR(dispatch_after_f, when, queue, context, work);
+  WRAP(dispatch_after)(when, queue, ^{
+    work(context);
+  });
+}
+
 // GCD's dispatch_once implementation has a fast path that contains a racy read
 // and it's inlined into user's code. Furthermore, this fast path doesn't
 // establish a proper happens-before relations between the initialization and
 // code following the call to dispatch_once. We could deal with this in
 // instrumented code, but there's not much we can do about it in system
 // libraries. Let's disable the fast path (by never storing the value ~0 to
 // predicate), so the interceptor is always called, and let's add proper release
 // and acquire semantics. Since TSan does not see its own atomic stores, the

test/tsan/Darwin/gcd-after.mm

+// 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;
+long my_global2;
+
+void callback(void *context) {
+  my_global2 = 42;
+
+  dispatch_async(dispatch_get_main_queue(), ^{
+    CFRunLoopStop(CFRunLoopGetMain());
+  });
+}
+
+int main(int argc, const char *argv[]) {
+  fprintf(stderr, "start\n");
+
+  my_global = 10;
+  dispatch_queue_t q = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
+  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(10 * NSEC_PER_MSEC)), q, ^{
+    my_global = 42;
+
+    dispatch_async(dispatch_get_main_queue(), ^{
+      CFRunLoopStop(CFRunLoopGetMain());
+    });
+  });
+  CFRunLoopRun();
+
+  my_global2 = 10;
+  dispatch_after_f(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(10 * NSEC_PER_MSEC)), q, NULL, &callback);
+  CFRunLoopRun();
+
+  fprintf(stderr, "done\n");
+  return 0;
+}
+
+// CHECK: start
+// CHECK: done
+// CHECK-NOT: WARNING: ThreadSanitizer