From afedb893a6149b73c835d55dbd5690e8068b0c13 Mon Sep 17 00:00:00 2001
From: Vitaly Buka <vitalybuka@google.com>
Date: Tue, 20 Nov 2018 18:21:42 +0000
Subject: [PATCH] [tsan] Add __cxa_guard_acquire hooks to support cooperative
 scheduling

Reviewers: dvyukov

Subscribers: krytarowski, kubamracek, llvm-commits

Differential Revision: https://reviews.llvm.org/D54664

llvm-svn: 347336
---
 compiler-rt/lib/tsan/rtl/tsan_interceptors.cc | 12 +++++++++
 compiler-rt/test/tsan/cxa_guard_acquire.cc    | 25 +++++++++++++++++++
 2 files changed, 37 insertions(+)
 create mode 100644 compiler-rt/test/tsan/cxa_guard_acquire.cc

diff --git a/compiler-rt/lib/tsan/rtl/tsan_interceptors.cc b/compiler-rt/lib/tsan/rtl/tsan_interceptors.cc
index a8d2feaa31c8..801478a00151 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_interceptors.cc
+++ b/compiler-rt/lib/tsan/rtl/tsan_interceptors.cc
@@ -228,6 +228,16 @@ void InitializeLibIgnore() {
   libignore()->OnLibraryLoaded(0);
 }
 
+// The following two hooks can be used by for cooperative scheduling when
+// locking.
+#ifdef TSAN_EXTERNAL_HOOKS
+void OnPotentiallyBlockingRegionBegin();
+void OnPotentiallyBlockingRegionEnd();
+#else
+SANITIZER_WEAK_CXX_DEFAULT_IMPL void OnPotentiallyBlockingRegionBegin() {}
+SANITIZER_WEAK_CXX_DEFAULT_IMPL void OnPotentiallyBlockingRegionEnd() {}
+#endif
+
 }  // namespace __tsan
 
 static ThreadSignalContext *SigCtx(ThreadState *thr) {
@@ -866,6 +876,8 @@ TSAN_INTERCEPTOR(int, posix_memalign, void **memptr, uptr align, uptr sz) {
 // Used in thread-safe function static initialization.
 STDCXX_INTERCEPTOR(int, __cxa_guard_acquire, atomic_uint32_t *g) {
   SCOPED_INTERCEPTOR_RAW(__cxa_guard_acquire, g);
+  OnPotentiallyBlockingRegionBegin();
+  auto on_exit = at_scope_exit(&OnPotentiallyBlockingRegionEnd);
   for (;;) {
     u32 cmp = atomic_load(g, memory_order_acquire);
     if (cmp == 0) {
diff --git a/compiler-rt/test/tsan/cxa_guard_acquire.cc b/compiler-rt/test/tsan/cxa_guard_acquire.cc
new file mode 100644
index 000000000000..cdbe609003d4
--- /dev/null
+++ b/compiler-rt/test/tsan/cxa_guard_acquire.cc
@@ -0,0 +1,25 @@
+// RUN: %clangxx_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
+
+#include <stdio.h>
+
+namespace __tsan {
+
+void OnPotentiallyBlockingRegionBegin() {
+  printf("Enter __cxa_guard_acquire\n");
+}
+
+void OnPotentiallyBlockingRegionEnd() { printf("Exit __cxa_guard_acquire\n"); }
+
+} // namespace __tsan
+
+int main(int argc, char **argv) {
+  // CHECK: Enter main
+  printf("Enter main\n");
+  // CHECK-NEXT: Enter __cxa_guard_acquire
+  // CHECK-NEXT: Exit __cxa_guard_acquire
+  static int s = argc;
+  (void)s;
+  // CHECK-NEXT: Exit main
+  printf("Exit main\n");
+  return 0;
+}