[tsan] Avoid false positives with GCD data callbacks

This patch adds synchronization between the creation of the GCD data object and destructor’s execution. It’s far from perfect, because ideally we’d want to synchronize the destruction of the last reference (via dispatch_release) and the destructor’s execution, but intercepting objc_release is problematic.

Differential Revision: http://reviews.llvm.org/D21990



git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@274749 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 62 insertions, 0 deletions

diff --git a/lib/tsan/rtl/tsan_libdispatch_mac.cc b/lib/tsan/rtl/tsan_libdispatch_mac.cc
index cde5ed0a1..15805b98d 100644
--- a/lib/tsan/rtl/tsan_libdispatch_mac.cc
+++ b/lib/tsan/rtl/tsan_libdispatch_mac.cc
@@ -475,6 +475,32 @@ TSAN_INTERCEPTOR(void, dispatch_apply_f, size_t iterations,
   WRAP(dispatch_apply)(iterations, queue, new_block);
 }
 
+DECLARE_REAL_AND_INTERCEPTOR(void, free, void *ptr)
+DECLARE_REAL_AND_INTERCEPTOR(int, munmap, void *addr, long_t sz)
+
+TSAN_INTERCEPTOR(dispatch_data_t, dispatch_data_create, const void *buffer,
+                 size_t size, dispatch_queue_t q, dispatch_block_t destructor) {
+  SCOPED_TSAN_INTERCEPTOR(dispatch_data_create, buffer, size, q, destructor);
+  if ((q == nullptr) || (destructor == DISPATCH_DATA_DESTRUCTOR_DEFAULT))
+    return REAL(dispatch_data_create)(buffer, size, q, destructor);
+
+  if (destructor == DISPATCH_DATA_DESTRUCTOR_FREE)
+    destructor = ^(void) { WRAP(free)((void *)buffer); };
+  else if (destructor == DISPATCH_DATA_DESTRUCTOR_MUNMAP)
+    destructor = ^(void) { WRAP(munmap)((void *)buffer, size); };
+
+  SCOPED_TSAN_INTERCEPTOR_USER_CALLBACK_START();
+  dispatch_block_t heap_block = Block_copy(destructor);
+  SCOPED_TSAN_INTERCEPTOR_USER_CALLBACK_END();
+  tsan_block_context_t *new_context =
+      AllocContext(thr, pc, q, heap_block, &invoke_and_release_block);
+  uptr submit_sync = (uptr)new_context;
+  Release(thr, pc, submit_sync);
+  return REAL(dispatch_data_create)(buffer, size, q, ^(void) {
+    dispatch_callback_wrap(new_context);
+  });
+}
+
 }  // namespace __tsan
 
 #endif  // SANITIZER_MAC
diff --git a/test/tsan/Darwin/gcd-data.mm b/test/tsan/Darwin/gcd-data.mm
new file mode 100644
index 000000000..a5154dc35
--- /dev/null
+++ b/test/tsan/Darwin/gcd-data.mm
@@ -0,0 +1,36 @@
+// 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 global;
+
+int main(int argc, const char *argv[]) {
+  fprintf(stderr, "Hello world.\n");
+
+  dispatch_queue_t q = dispatch_queue_create("my.queue", DISPATCH_QUEUE_SERIAL);
+  dispatch_semaphore_t sem = dispatch_semaphore_create(0);
+
+  global = 44;
+  dispatch_data_t data = dispatch_data_create("buffer", 6, q, ^{
+    fprintf(stderr, "Data destructor.\n");
+    global++;
+
+    dispatch_semaphore_signal(sem);
+  });
+  dispatch_release(data);
+  data = nil;
+
+  dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
+
+  data = dispatch_data_create("buffer", 6, q, DISPATCH_DATA_DESTRUCTOR_DEFAULT);
+  dispatch_release(data);
+  data = nil;
+
+  fprintf(stderr, "Done.\n");
+}
+
+// CHECK: Hello world.
+// CHECK: Data destructor.
+// CHECK-NOT: WARNING: ThreadSanitizer
+// CHECK: Done.