diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config
index 69ace386dd7..543fac268b4 100644
--- a/libstdc++-v3/include/bits/c++config
+++ b/libstdc++-v3/include/bits/c++config
@@ -126,20 +126,29 @@
 # define _GLIBCXX_ABI_TAG_CXX11 __attribute ((__abi_tag__ ("cxx11")))
 #endif
 
 // Macro to warn about unused results.
 #if __cplusplus >= 201703L
 # define _GLIBCXX_NODISCARD [[__nodiscard__]]
 #else
 # define _GLIBCXX_NODISCARD
 #endif
 
+// Macro for TSAN.
+#if __SANITIZE_THREAD__
+#  define _GLIBCXX_TSAN 1
+#elif defined __has_feature
+# if __has_feature(thread_sanitizer)
+#  define _GLIBCXX_TSAN 1
+# endif
+#endif
+
 
 
 #if __cplusplus
 
 // Macro for constexpr, to support in mixed 03/0x mode.
 #ifndef _GLIBCXX_CONSTEXPR
 # if __cplusplus >= 201103L
 #  define _GLIBCXX_CONSTEXPR constexpr
 #  define _GLIBCXX_USE_CONSTEXPR constexpr
 # else
diff --git a/libstdc++-v3/include/bits/shared_ptr_base.h b/libstdc++-v3/include/bits/shared_ptr_base.h
index 5be935d174d..834ca13bdc6 100644
--- a/libstdc++-v3/include/bits/shared_ptr_base.h
+++ b/libstdc++-v3/include/bits/shared_ptr_base.h
@@ -153,20 +153,93 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	if (!_M_add_ref_lock_nothrow())
 	  __throw_bad_weak_ptr();
       }
 
       bool
       _M_add_ref_lock_nothrow() noexcept;
 
       void
       _M_release() noexcept
       {
+#if _GLIBCXX_TSAN
+        _M_release_orig();
+        return;
+#endif
+        constexpr bool __lock_free
+          = __atomic_always_lock_free(sizeof(long long), 0)
+          && __atomic_always_lock_free(sizeof(_Atomic_word), 0);
+        constexpr bool __double_word
+          = sizeof(long long) == 2 * sizeof(_Atomic_word);
+        // The ref-count members follow the vptr, so are aligned to
+        // alignof(void*).
+        constexpr bool __aligned = alignof(long long) <= alignof(void*);
+        if _GLIBCXX17_CONSTEXPR
+          (__lock_free && __double_word && __aligned)
+          {
+            _M_release_double_width_cas();
+            return;
+          }
+        else
+          {
+            _M_release_orig();
+          }
+      }
+
+      void
+      _M_release_double_width_cas() noexcept
+      {
+        _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_use_count);
+        _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count);
+        if (__atomic_load_n((long long*)(&_M_use_count), __ATOMIC_ACQUIRE)
+            == (1LL + (1LL << (__CHAR_BIT__ * sizeof(_Atomic_word)))))
+          {
+            // Both counts are 1, so there are no weak references and
+            // we are releasing the last strong reference. No other
+            // threads can observe the effects of this _M_release()
+            // call (e.g. calling use_count()) without a data race.
+            *(long long*)(&_M_use_count) = 0;
+            _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_use_count);
+            _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count);
+            _M_dispose();
+            _M_destroy();
+          }
+        else
+          {
+            if ((__gnu_cxx::__exchange_and_add(&_M_use_count, -1) == 1))
+              {
+                _M_release_last_use();
+              }
+          }
+      }
+
+      void
+      __attribute__ ((noinline))
+      _M_release_last_use() noexcept
+      {
+        _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_use_count);
+        _M_dispose();
+        if (_Mutex_base<_Lp>::_S_need_barriers)
+          {
+            __atomic_thread_fence (__ATOMIC_ACQ_REL);
+          }
+        _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count);
+        if (__gnu_cxx::__exchange_and_add_dispatch(&_M_weak_count,
+                                                   -1) == 1)
+          {
+            _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_weak_count);
+            _M_destroy();
+          }
+      }
+
+      void
+      _M_release_orig() noexcept
+      {
         // Be race-detector-friendly.  For more info see bits/c++config.
         _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_use_count);
 	if (__gnu_cxx::__exchange_and_add_dispatch(&_M_use_count, -1) == 1)
 	  {
             _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(&_M_use_count);
 	    _M_dispose();
 	    // There must be a memory barrier between dispose() and destroy()
 	    // to ensure that the effects of dispose() are observed in the
 	    // thread that runs destroy().
 	    // See http://gcc.gnu.org/ml/libstdc++/2005-11/msg00136.html
@@ -279,20 +352,27 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     _Sp_counted_base<_S_single>::_M_release() noexcept
     {
       if (--_M_use_count == 0)
         {
           _M_dispose();
           if (--_M_weak_count == 0)
             _M_destroy();
         }
     }
 
+  template<>
+    inline void
+    _Sp_counted_base<_S_mutex>::_M_release() noexcept
+    {
+      _M_release_orig();
+    }
+
   template<>
     inline void
     _Sp_counted_base<_S_single>::_M_weak_add_ref() noexcept
     { ++_M_weak_count; }
 
   template<>
     inline void
     _Sp_counted_base<_S_single>::_M_weak_release() noexcept
     {
       if (--_M_weak_count == 0)