Index: lib/msan/msan.cc
===================================================================
--- lib/msan/msan.cc
+++ lib/msan/msan.cc
@@ -220,7 +220,7 @@
 void GetStackTrace(BufferedStackTrace *stack, uptr max_s, uptr pc, uptr bp,
                    bool request_fast_unwind) {
   MsanThread *t = GetCurrentThread();
-  if (!t || !StackTrace::WillUseFastUnwind(request_fast_unwind)) {
+  if (!t || !request_fast_unwind) {
     // Block reports from our interceptors during _Unwind_Backtrace.
     SymbolizerScope sym_scope;
     return stack->Unwind(max_s, pc, bp, nullptr, 0, 0, request_fast_unwind);
Index: lib/sanitizer_common/sanitizer_stacktrace.h
===================================================================
--- lib/sanitizer_common/sanitizer_stacktrace.h
+++ lib/sanitizer_common/sanitizer_stacktrace.h
@@ -27,15 +27,6 @@
 # define SANITIZER_CAN_FAST_UNWIND 1
 #endif
 
-// Fast unwind is the only option on Mac for now; we will need to
-// revisit this macro when slow unwind works on Mac, see
-// https://github.com/google/sanitizers/issues/137
-#if SANITIZER_MAC
-# define SANITIZER_CAN_SLOW_UNWIND 0
-#else
-# define SANITIZER_CAN_SLOW_UNWIND 1
-#endif
-
 struct StackTrace {
   const uptr *trace;
   u32 size;
@@ -54,14 +45,6 @@
   // Prints a symbolized stacktrace, followed by an empty line.
   void Print() const;
 
-  static bool WillUseFastUnwind(bool request_fast_unwind) {
-    if (!SANITIZER_CAN_FAST_UNWIND)
-      return false;
-    else if (!SANITIZER_CAN_SLOW_UNWIND)
-      return true;
-    return request_fast_unwind;
-  }
-
   static uptr GetCurrentPc();
   static inline uptr GetPreviousInstructionPc(uptr pc);
   static uptr GetNextInstructionPc(uptr pc);
Index: lib/sanitizer_common/sanitizer_stacktrace_libcdep.cc
===================================================================
--- lib/sanitizer_common/sanitizer_stacktrace_libcdep.cc
+++ lib/sanitizer_common/sanitizer_stacktrace_libcdep.cc
@@ -68,7 +68,7 @@
     trace_buffer[0] = pc;
     return;
   }
-  if (!WillUseFastUnwind(request_fast_unwind)) {
+  if (!request_fast_unwind) {
 #if SANITIZER_CAN_SLOW_UNWIND
     if (context)
       SlowUnwindStackWithContext(pc, context, max_depth);
Index: lib/sanitizer_common/tests/sanitizer_stacktrace_test.cc
===================================================================
--- lib/sanitizer_common/tests/sanitizer_stacktrace_test.cc
+++ lib/sanitizer_common/tests/sanitizer_stacktrace_test.cc
@@ -22,8 +22,6 @@
   virtual void SetUp();
   virtual void TearDown();
   bool TryFastUnwind(uptr max_depth) {
-    if (!StackTrace::WillUseFastUnwind(true))
-      return false;
     trace.Unwind(max_depth, start_pc, (uptr)&fake_stack[0], 0, fake_top,
                  fake_bottom, true);
     return true;
@@ -150,8 +148,6 @@
 }
 
 TEST(SlowUnwindTest, ShortStackTrace) {
-  if (StackTrace::WillUseFastUnwind(false))
-    return;
   BufferedStackTrace stack;
   uptr pc = StackTrace::GetCurrentPc();
   uptr bp = GET_CURRENT_FRAME();
Index: lib/tsan/rtl/tsan_rtl_report.cc
===================================================================
--- lib/tsan/rtl/tsan_rtl_report.cc
+++ lib/tsan/rtl/tsan_rtl_report.cc
@@ -694,6 +694,29 @@
   PrintStack(SymbolizeStack(trace));
 }
 
+#if !SANITIZER_GO
+static inline void ReverseStackTrace(BufferedStackTrace *ptrace) {
+  for (uptr i = 0; i < ptrace->size / 2; i++) {
+    uptr tmp = ptrace->trace_buffer[i];
+    ptrace->trace_buffer[i] = ptrace->trace_buffer[ptrace->size - i - 1];
+    ptrace->trace_buffer[ptrace->size - i - 1] = tmp;
+  }
+}
+
+static inline void PrintStackTrace(u32 max_depth, uptr pc, uptr bp,
+                                   void *context, uptr stack_top,
+                                   uptr stack_bottom,
+                                   bool request_fast_unwind) {
+  BufferedStackTrace *ptrace =
+      new(internal_alloc(MBlockStackTrace, sizeof(BufferedStackTrace)))
+          BufferedStackTrace();
+  ptrace->Unwind(max_depth, pc, bp, context, stack_top, stack_bottom,
+                 request_fast_unwind);
+  ReverseStackTrace(ptrace);
+  PrintStack(SymbolizeStack(*ptrace));
+}
+#endif
+
 // Always inlining PrintCurrentStackSlow, because LocatePcInTrace assumes
 // __sanitizer_print_stack_trace exists in the actual unwinded stack, but
 // tail-call to PrintCurrentStackSlow breaks this assumption because
@@ -704,16 +727,7 @@
 ALWAYS_INLINE
 void PrintCurrentStackSlow(uptr pc) {
 #if !SANITIZER_GO
-  BufferedStackTrace *ptrace =
-      new(internal_alloc(MBlockStackTrace, sizeof(BufferedStackTrace)))
-          BufferedStackTrace();
-  ptrace->Unwind(kStackTraceMax, pc, 0, 0, 0, 0, false);
-  for (uptr i = 0; i < ptrace->size / 2; i++) {
-    uptr tmp = ptrace->trace_buffer[i];
-    ptrace->trace_buffer[i] = ptrace->trace_buffer[ptrace->size - i - 1];
-    ptrace->trace_buffer[ptrace->size - i - 1] = tmp;
-  }
-  PrintStack(SymbolizeStack(*ptrace));
+  PrintStackTrace(kStackTraceMax, pc, 0, nullptr, 0, 0, false);
 #endif
 }
 
@@ -724,6 +738,20 @@
 extern "C" {
 SANITIZER_INTERFACE_ATTRIBUTE
 void __sanitizer_print_stack_trace() {
-  PrintCurrentStackSlow(StackTrace::GetCurrentPc());
+#if !SANITIZER_GO
+  uptr pc = StackTrace::GetCurrentPc();
+  bool request_fast_unwind = common_flags()->fast_unwind_on_fatal;
+  if (!request_fast_unwind) {
+    PrintCurrentStackSlow(pc);
+    return;
+  }
+
+  uptr top = 0;
+  uptr bottom = 0;
+  __sanitizer::GetThreadStackTopAndBottom(false, &top, &bottom);
+  uptr bp = GET_CURRENT_FRAME();
+  PrintStackTrace(kStackTraceMax, pc, bp, nullptr, top, bottom,
+                  request_fast_unwind);
+#endif
 }
 }  // extern "C"
Index: test/tsan/print_stack_trace.cc
===================================================================
--- /dev/null
+++ test/tsan/print_stack_trace.cc
@@ -0,0 +1,19 @@
+// Test for __sanitizer_print_stack_trace implementation.
+
+// RUN: %clangxx_tsan -O0 %s -o %t && TSAN_OPTIONS=stack_trace_format=DEFAULT:fast_unwind_on_fatal=0 %run %t 2>&1 | FileCheck %s
+// RUN: %clangxx_tsan -O0 %s -o %t && TSAN_OPTIONS=stack_trace_format=DEFAULT:fast_unwind_on_fatal=1 %run %t 2>&1 | FileCheck %s  --check-prefix=CHECK-FAST-UNWIND
+
+#include <sanitizer/common_interface_defs.h>
+
+static inline void FooBarBaz() {
+  __sanitizer_print_stack_trace();
+}
+
+int main() {
+  FooBarBaz();
+  return 0;
+}
+
+// CHECK: {{.*}} in __sanitizer_print_stack_trace{{.*}}
+// CHECK-FAST-UNWIND: {{.*}} in FooBarBaz{{.*}}
+// CHECK-FAST-UNWIND: {{.*}} in main{{.*}}