Index: compiler-rt/lib/asan/asan_thread.h
===================================================================
--- compiler-rt/lib/asan/asan_thread.h
+++ compiler-rt/lib/asan/asan_thread.h
@@ -68,7 +68,7 @@
   void Destroy();
 
   struct InitOptions;
-  void Init(const InitOptions *options = nullptr);
+  void Init(const InitOptions *options = nullptr, bool init_fake_stack = false);
 
   thread_return_t ThreadStart(tid_t os_id,
                               atomic_uintptr_t *signal_thread_is_registered);
Index: compiler-rt/lib/asan/asan_thread.cc
===================================================================
--- compiler-rt/lib/asan/asan_thread.cc
+++ compiler-rt/lib/asan/asan_thread.cc
@@ -222,16 +222,18 @@
   return nullptr;
 }
 
-void AsanThread::Init(const InitOptions *options) {
+void AsanThread::Init(const InitOptions *options, bool init_fake_stack) {
   next_stack_top_ = next_stack_bottom_ = 0;
   atomic_store(&stack_switching_, false, memory_order_release);
-  fake_stack_ = nullptr;  // Will be initialized lazily if needed.
+  fake_stack_ = nullptr;  // Will be initialized below, or lazily if needed.
   CHECK_EQ(this->stack_size(), 0U);
   SetThreadStackAndTls(options);
   CHECK_GT(this->stack_size(), 0U);
   CHECK(AddrIsInMem(stack_bottom_));
   CHECK(AddrIsInMem(stack_top_ - 1));
   ClearShadowForThreadStackAndTLS();
+  if (__asan_option_detect_stack_use_after_return && init_fake_stack)
+    AsyncSignalSafeLazyInitFakeStack();
   int local = 0;
   VReport(1, "T%d: stack [%p,%p) size 0x%zx; local=%p\n", tid(),
           (void *)stack_bottom_, (void *)stack_top_, stack_top_ - stack_bottom_,