diff --git a/libcxx/docs/ReleaseNotes.rst b/libcxx/docs/ReleaseNotes.rst
--- a/libcxx/docs/ReleaseNotes.rst
+++ b/libcxx/docs/ReleaseNotes.rst
@@ -62,7 +62,8 @@
   includes are removed based on the language version used. Incidental transitive
   inclusions of the following headers have been removed:
 
-  - C++2b: ``atomic``, ``bit``, ``cstring``, ``type_traits``
+  - C++2b: ``atomic``, ``bit``, ``cstdint``, ``cstdlib``, ``cstring``, ``initializer_list``, ``new``, ``stdexcept``,
+           ``type_traits``, ``typeinfo``
 
 - The headers ``<experimental/algorithm>`` and ``<experimental/functional>`` have been removed, since all the contents
   have been implemented in namespace ``std`` for at least two releases.
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -294,6 +294,7 @@
   __concepts/semiregular.h
   __concepts/swappable.h
   __concepts/totally_ordered.h
+  __condition_variable/condition_variable.h
   __config
   __coroutine/coroutine_handle.h
   __coroutine/coroutine_traits.h
@@ -474,7 +475,10 @@
   __memory_resource/pool_options.h
   __memory_resource/synchronized_pool_resource.h
   __memory_resource/unsynchronized_pool_resource.h
-  __mutex_base
+  __mutex/lock_guard.h
+  __mutex/mutex.h
+  __mutex/tag_types.h
+  __mutex/unique_lock.h
   __node_handle
   __numeric/accumulate.h
   __numeric/adjacent_difference.h
diff --git a/libcxx/include/__condition_variable/condition_variable.h b/libcxx/include/__condition_variable/condition_variable.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__condition_variable/condition_variable.h
@@ -0,0 +1,243 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___CONDITION_VARIABLE_CONDITION_VARIABLE_H
+#define _LIBCPP___CONDITION_VARIABLE_CONDITION_VARIABLE_H
+
+#include <__chrono/steady_clock.h>
+#include <__chrono/system_clock.h>
+#include <__chrono/time_point.h>
+#include <__config>
+#include <__mutex/mutex.h>
+#include <__mutex/unique_lock.h>
+#include <__threading_support>
+#include <__type_traits/enable_if.h>
+#include <__type_traits/is_floating_point.h>
+#include <__utility/move.h>
+#include <ratio>
+#include <system_error>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+#ifndef _LIBCPP_HAS_NO_THREADS
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// enum class cv_status
+_LIBCPP_DECLARE_STRONG_ENUM(cv_status){no_timeout, timeout};
+_LIBCPP_DECLARE_STRONG_ENUM_EPILOG(cv_status)
+
+class _LIBCPP_TYPE_VIS condition_variable {
+  __libcpp_condvar_t __cv_ = _LIBCPP_CONDVAR_INITIALIZER;
+
+public:
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR condition_variable() _NOEXCEPT = default;
+
+#  ifdef _LIBCPP_HAS_TRIVIAL_CONDVAR_DESTRUCTION
+  ~condition_variable() = default;
+#  else
+  ~condition_variable();
+#  endif
+
+  condition_variable(const condition_variable&)            = delete;
+  condition_variable& operator=(const condition_variable&) = delete;
+
+  void notify_one() _NOEXCEPT;
+  void notify_all() _NOEXCEPT;
+
+  void wait(unique_lock<mutex>& __lk) _NOEXCEPT;
+  template <class _Predicate>
+  _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS void wait(unique_lock<mutex>& __lk, _Predicate __pred);
+
+  template <class _Clock, class _Duration>
+  _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS cv_status
+  wait_until(unique_lock<mutex>& __lk, const chrono::time_point<_Clock, _Duration>& __t);
+
+  template <class _Clock, class _Duration, class _Predicate>
+  _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS bool
+  wait_until(unique_lock<mutex>& __lk, const chrono::time_point<_Clock, _Duration>& __t, _Predicate __pred);
+
+  template <class _Rep, class _Period>
+  _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS cv_status
+  wait_for(unique_lock<mutex>& __lk, const chrono::duration<_Rep, _Period>& __d);
+
+  template <class _Rep, class _Period, class _Predicate>
+  bool _LIBCPP_HIDE_FROM_ABI
+  wait_for(unique_lock<mutex>& __lk, const chrono::duration<_Rep, _Period>& __d, _Predicate __pred);
+
+  typedef __libcpp_condvar_t* native_handle_type;
+  _LIBCPP_HIDE_FROM_ABI native_handle_type native_handle() { return &__cv_; }
+
+private:
+  void
+  __do_timed_wait(unique_lock<mutex>& __lk, chrono::time_point<chrono::system_clock, chrono::nanoseconds>) _NOEXCEPT;
+#  if defined(_LIBCPP_HAS_COND_CLOCKWAIT)
+  void
+  __do_timed_wait(unique_lock<mutex>& __lk, chrono::time_point<chrono::steady_clock, chrono::nanoseconds>) _NOEXCEPT;
+#  endif
+  template <class _Clock>
+  void __do_timed_wait(unique_lock<mutex>& __lk, chrono::time_point<_Clock, chrono::nanoseconds>) _NOEXCEPT;
+};
+#endif // !_LIBCPP_HAS_NO_THREADS
+
+template <class _Rep, class _Period>
+inline _LIBCPP_HIDE_FROM_ABI __enable_if_t<is_floating_point<_Rep>::value, chrono::nanoseconds>
+__safe_nanosecond_cast(chrono::duration<_Rep, _Period> __d) {
+  using namespace chrono;
+  using __ratio       = ratio_divide<_Period, nano>;
+  using __ns_rep      = nanoseconds::rep;
+  _Rep __result_float = __d.count() * __ratio::num / __ratio::den;
+
+  _Rep __result_max = numeric_limits<__ns_rep>::max();
+  if (__result_float >= __result_max) {
+    return nanoseconds::max();
+  }
+
+  _Rep __result_min = numeric_limits<__ns_rep>::min();
+  if (__result_float <= __result_min) {
+    return nanoseconds::min();
+  }
+
+  return nanoseconds(static_cast<__ns_rep>(__result_float));
+}
+
+template <class _Rep, class _Period>
+inline _LIBCPP_HIDE_FROM_ABI __enable_if_t<!is_floating_point<_Rep>::value, chrono::nanoseconds>
+__safe_nanosecond_cast(chrono::duration<_Rep, _Period> __d) {
+  using namespace chrono;
+  if (__d.count() == 0) {
+    return nanoseconds(0);
+  }
+
+  using __ratio         = ratio_divide<_Period, nano>;
+  using __ns_rep        = nanoseconds::rep;
+  __ns_rep __result_max = numeric_limits<__ns_rep>::max();
+  if (__d.count() > 0 && __d.count() > __result_max / __ratio::num) {
+    return nanoseconds::max();
+  }
+
+  __ns_rep __result_min = numeric_limits<__ns_rep>::min();
+  if (__d.count() < 0 && __d.count() < __result_min / __ratio::num) {
+    return nanoseconds::min();
+  }
+
+  __ns_rep __result = __d.count() * __ratio::num / __ratio::den;
+  if (__result == 0) {
+    return nanoseconds(1);
+  }
+
+  return nanoseconds(__result);
+}
+
+#ifndef _LIBCPP_HAS_NO_THREADS
+template <class _Predicate>
+void condition_variable::wait(unique_lock<mutex>& __lk, _Predicate __pred) {
+  while (!__pred())
+    wait(__lk);
+}
+
+template <class _Clock, class _Duration>
+cv_status condition_variable::wait_until(unique_lock<mutex>& __lk, const chrono::time_point<_Clock, _Duration>& __t) {
+  using namespace chrono;
+  using __clock_tp_ns = time_point<_Clock, nanoseconds>;
+
+  typename _Clock::time_point __now = _Clock::now();
+  if (__t <= __now)
+    return cv_status::timeout;
+
+  __clock_tp_ns __t_ns = __clock_tp_ns(std::__safe_nanosecond_cast(__t.time_since_epoch()));
+
+  __do_timed_wait(__lk, __t_ns);
+  return _Clock::now() < __t ? cv_status::no_timeout : cv_status::timeout;
+}
+
+template <class _Clock, class _Duration, class _Predicate>
+bool condition_variable::wait_until(
+    unique_lock<mutex>& __lk, const chrono::time_point<_Clock, _Duration>& __t, _Predicate __pred) {
+  while (!__pred()) {
+    if (wait_until(__lk, __t) == cv_status::timeout)
+      return __pred();
+  }
+  return true;
+}
+
+template <class _Rep, class _Period>
+cv_status condition_variable::wait_for(unique_lock<mutex>& __lk, const chrono::duration<_Rep, _Period>& __d) {
+  using namespace chrono;
+  if (__d <= __d.zero())
+    return cv_status::timeout;
+  using __ns_rep                   = nanoseconds::rep;
+  steady_clock::time_point __c_now = steady_clock::now();
+
+#  if defined(_LIBCPP_HAS_COND_CLOCKWAIT)
+  using __clock_tp_ns     = time_point<steady_clock, nanoseconds>;
+  __ns_rep __now_count_ns = std::__safe_nanosecond_cast(__c_now.time_since_epoch()).count();
+#  else
+  using __clock_tp_ns     = time_point<system_clock, nanoseconds>;
+  __ns_rep __now_count_ns = std::__safe_nanosecond_cast(system_clock::now().time_since_epoch()).count();
+#  endif
+
+  __ns_rep __d_ns_count = std::__safe_nanosecond_cast(__d).count();
+
+  if (__now_count_ns > numeric_limits<__ns_rep>::max() - __d_ns_count) {
+    __do_timed_wait(__lk, __clock_tp_ns::max());
+  } else {
+    __do_timed_wait(__lk, __clock_tp_ns(nanoseconds(__now_count_ns + __d_ns_count)));
+  }
+
+  return steady_clock::now() - __c_now < __d ? cv_status::no_timeout : cv_status::timeout;
+}
+
+template <class _Rep, class _Period, class _Predicate>
+inline bool
+condition_variable::wait_for(unique_lock<mutex>& __lk, const chrono::duration<_Rep, _Period>& __d, _Predicate __pred) {
+  return wait_until(__lk, chrono::steady_clock::now() + __d, std::move(__pred));
+}
+
+#  if defined(_LIBCPP_HAS_COND_CLOCKWAIT)
+inline void condition_variable::__do_timed_wait(
+    unique_lock<mutex>& __lk, chrono::time_point<chrono::steady_clock, chrono::nanoseconds> __tp) _NOEXCEPT {
+  using namespace chrono;
+  if (!__lk.owns_lock())
+    __throw_system_error(EPERM, "condition_variable::timed wait: mutex not locked");
+  nanoseconds __d = __tp.time_since_epoch();
+  timespec __ts;
+  seconds __s                 = duration_cast<seconds>(__d);
+  using __ts_sec              = decltype(__ts.tv_sec);
+  const __ts_sec __ts_sec_max = numeric_limits<__ts_sec>::max();
+  if (__s.count() < __ts_sec_max) {
+    __ts.tv_sec  = static_cast<__ts_sec>(__s.count());
+    __ts.tv_nsec = (__d - __s).count();
+  } else {
+    __ts.tv_sec  = __ts_sec_max;
+    __ts.tv_nsec = giga::num - 1;
+  }
+  int __ec = pthread_cond_clockwait(&__cv_, __lk.mutex()->native_handle(), CLOCK_MONOTONIC, &__ts);
+  if (__ec != 0 && __ec != ETIMEDOUT)
+    __throw_system_error(__ec, "condition_variable timed_wait failed");
+}
+#  endif // _LIBCPP_HAS_COND_CLOCKWAIT
+
+template <class _Clock>
+inline void condition_variable::__do_timed_wait(unique_lock<mutex>& __lk,
+                                                chrono::time_point<_Clock, chrono::nanoseconds> __tp) _NOEXCEPT {
+  wait_for(__lk, __tp - _Clock::now());
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_HAS_NO_THREADS
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP___CONDITION_VARIABLE_CONDITION_VARIABLE_H
diff --git a/libcxx/include/__mutex/lock_guard.h b/libcxx/include/__mutex/lock_guard.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__mutex/lock_guard.h
@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___MUTEX_LOCK_GUARD_H
+#define _LIBCPP___MUTEX_LOCK_GUARD_H
+
+#include <__config>
+#include <__mutex/tag_types.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#ifndef _LIBCPP_HAS_NO_THREADS
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Mutex>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_THREAD_SAFETY_ANNOTATION(scoped_lockable) lock_guard {
+public:
+  typedef _Mutex mutex_type;
+
+private:
+  mutex_type& __m_;
+
+public:
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI explicit lock_guard(mutex_type& __m)
+      _LIBCPP_THREAD_SAFETY_ANNOTATION(acquire_capability(__m))
+      : __m_(__m) {
+    __m_.lock();
+  }
+
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI lock_guard(mutex_type& __m, adopt_lock_t)
+      _LIBCPP_THREAD_SAFETY_ANNOTATION(requires_capability(__m))
+      : __m_(__m) {}
+  _LIBCPP_HIDE_FROM_ABI ~lock_guard() _LIBCPP_THREAD_SAFETY_ANNOTATION(release_capability()) { __m_.unlock(); }
+
+private:
+  lock_guard(lock_guard const&)            = delete;
+  lock_guard& operator=(lock_guard const&) = delete;
+};
+_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(lock_guard);
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_HAS_NO_THREADS
+
+#endif // _LIBCPP___MUTEX_LOCK_GUARD_H
diff --git a/libcxx/include/__mutex/mutex.h b/libcxx/include/__mutex/mutex.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__mutex/mutex.h
@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___MUTEX_MUTEX_H
+#define _LIBCPP___MUTEX_MUTEX_H
+
+#include <__config>
+#include <__threading_support>
+#include <__type_traits/is_nothrow_default_constructible.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#ifndef _LIBCPP_HAS_NO_THREADS
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+class _LIBCPP_TYPE_VIS _LIBCPP_THREAD_SAFETY_ANNOTATION(capability("mutex")) mutex {
+  __libcpp_mutex_t __m_ = _LIBCPP_MUTEX_INITIALIZER;
+
+public:
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR mutex() = default;
+
+  mutex(const mutex&)            = delete;
+  mutex& operator=(const mutex&) = delete;
+
+#  if defined(_LIBCPP_HAS_TRIVIAL_MUTEX_DESTRUCTION)
+  ~mutex() = default;
+#  else
+  ~mutex() _NOEXCEPT;
+#  endif
+
+  void lock() _LIBCPP_THREAD_SAFETY_ANNOTATION(acquire_capability());
+  bool try_lock() _NOEXCEPT _LIBCPP_THREAD_SAFETY_ANNOTATION(try_acquire_capability(true));
+  void unlock() _NOEXCEPT _LIBCPP_THREAD_SAFETY_ANNOTATION(release_capability());
+
+  typedef __libcpp_mutex_t* native_handle_type;
+  _LIBCPP_HIDE_FROM_ABI native_handle_type native_handle() { return &__m_; }
+};
+
+static_assert(is_nothrow_default_constructible<mutex>::value, "the default constructor for std::mutex must be nothrow");
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_HAS_NO_THREADS
+
+#endif // _LIBCPP___MUTEX_MUTEX_H
diff --git a/libcxx/include/__mutex/tag_types.h b/libcxx/include/__mutex/tag_types.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__mutex/tag_types.h
@@ -0,0 +1,52 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___MUTEX_TAG_TYPES_H
+#define _LIBCPP___MUTEX_TAG_TYPES_H
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#ifndef _LIBCPP_HAS_NO_THREADS
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+struct _LIBCPP_TYPE_VIS defer_lock_t {
+  explicit defer_lock_t() = default;
+};
+
+struct _LIBCPP_TYPE_VIS try_to_lock_t {
+  explicit try_to_lock_t() = default;
+};
+
+struct _LIBCPP_TYPE_VIS adopt_lock_t {
+  explicit adopt_lock_t() = default;
+};
+
+#  if defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_LIBRARY)
+
+extern _LIBCPP_EXPORTED_FROM_ABI const defer_lock_t defer_lock;
+extern _LIBCPP_EXPORTED_FROM_ABI const try_to_lock_t try_to_lock;
+extern _LIBCPP_EXPORTED_FROM_ABI const adopt_lock_t adopt_lock;
+
+#  else
+
+/* inline */ constexpr defer_lock_t defer_lock   = defer_lock_t();
+/* inline */ constexpr try_to_lock_t try_to_lock = try_to_lock_t();
+/* inline */ constexpr adopt_lock_t adopt_lock   = adopt_lock_t();
+
+#  endif
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_HAS_NO_THREADS
+
+#endif // _LIBCPP___MUTEX_TAG_TYPES_H
diff --git a/libcxx/include/__mutex/unique_lock.h b/libcxx/include/__mutex/unique_lock.h
new file mode 100644
--- /dev/null
+++ b/libcxx/include/__mutex/unique_lock.h
@@ -0,0 +1,172 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___MUTEX_UNIQUE_LOCK_H
+#define _LIBCPP___MUTEX_UNIQUE_LOCK_H
+
+#include <__chrono/duration.h>
+#include <__chrono/time_point.h>
+#include <__config>
+#include <__memory/addressof.h>
+#include <__mutex/tag_types.h>
+#include <__utility/swap.h>
+#include <system_error>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#ifndef _LIBCPP_HAS_NO_THREADS
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Mutex>
+class _LIBCPP_TEMPLATE_VIS unique_lock {
+public:
+  typedef _Mutex mutex_type;
+
+private:
+  mutex_type* __m_;
+  bool __owns_;
+
+public:
+  _LIBCPP_HIDE_FROM_ABI unique_lock() _NOEXCEPT : __m_(nullptr), __owns_(false) {}
+  _LIBCPP_HIDE_FROM_ABI explicit unique_lock(mutex_type& __m) : __m_(std::addressof(__m)), __owns_(true) {
+    __m_->lock();
+  }
+
+  _LIBCPP_HIDE_FROM_ABI unique_lock(mutex_type& __m, defer_lock_t) _NOEXCEPT
+      : __m_(std::addressof(__m)),
+        __owns_(false) {}
+
+  _LIBCPP_HIDE_FROM_ABI unique_lock(mutex_type& __m, try_to_lock_t)
+      : __m_(std::addressof(__m)), __owns_(__m.try_lock()) {}
+
+  _LIBCPP_HIDE_FROM_ABI unique_lock(mutex_type& __m, adopt_lock_t) : __m_(std::addressof(__m)), __owns_(true) {}
+
+  template <class _Clock, class _Duration>
+  _LIBCPP_HIDE_FROM_ABI unique_lock(mutex_type& __m, const chrono::time_point<_Clock, _Duration>& __t)
+      : __m_(std::addressof(__m)), __owns_(__m.try_lock_until(__t)) {}
+
+  template <class _Rep, class _Period>
+  _LIBCPP_HIDE_FROM_ABI unique_lock(mutex_type& __m, const chrono::duration<_Rep, _Period>& __d)
+      : __m_(std::addressof(__m)), __owns_(__m.try_lock_for(__d)) {}
+
+  _LIBCPP_HIDE_FROM_ABI ~unique_lock() {
+    if (__owns_)
+      __m_->unlock();
+  }
+
+  unique_lock(unique_lock const&)            = delete;
+  unique_lock& operator=(unique_lock const&) = delete;
+
+  _LIBCPP_HIDE_FROM_ABI unique_lock(unique_lock&& __u) _NOEXCEPT : __m_(__u.__m_), __owns_(__u.__owns_) {
+    __u.__m_    = nullptr;
+    __u.__owns_ = false;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI unique_lock& operator=(unique_lock&& __u) _NOEXCEPT {
+    if (__owns_)
+      __m_->unlock();
+
+    __m_        = __u.__m_;
+    __owns_     = __u.__owns_;
+    __u.__m_    = nullptr;
+    __u.__owns_ = false;
+    return *this;
+  }
+
+  void lock();
+  bool try_lock();
+
+  template <class _Rep, class _Period>
+  bool try_lock_for(const chrono::duration<_Rep, _Period>& __d);
+
+  template <class _Clock, class _Duration>
+  bool try_lock_until(const chrono::time_point<_Clock, _Duration>& __t);
+
+  void unlock();
+
+  _LIBCPP_HIDE_FROM_ABI void swap(unique_lock& __u) _NOEXCEPT {
+    std::swap(__m_, __u.__m_);
+    std::swap(__owns_, __u.__owns_);
+  }
+
+  _LIBCPP_HIDE_FROM_ABI mutex_type* release() _NOEXCEPT {
+    mutex_type* __m = __m_;
+    __m_            = nullptr;
+    __owns_         = false;
+    return __m;
+  }
+
+  _LIBCPP_HIDE_FROM_ABI bool owns_lock() const _NOEXCEPT { return __owns_; }
+  _LIBCPP_HIDE_FROM_ABI explicit operator bool() const _NOEXCEPT { return __owns_; }
+  _LIBCPP_HIDE_FROM_ABI mutex_type* mutex() const _NOEXCEPT { return __m_; }
+};
+_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(unique_lock);
+
+template <class _Mutex>
+void unique_lock<_Mutex>::lock() {
+  if (__m_ == nullptr)
+    __throw_system_error(EPERM, "unique_lock::lock: references null mutex");
+  if (__owns_)
+    __throw_system_error(EDEADLK, "unique_lock::lock: already locked");
+  __m_->lock();
+  __owns_ = true;
+}
+
+template <class _Mutex>
+bool unique_lock<_Mutex>::try_lock() {
+  if (__m_ == nullptr)
+    __throw_system_error(EPERM, "unique_lock::try_lock: references null mutex");
+  if (__owns_)
+    __throw_system_error(EDEADLK, "unique_lock::try_lock: already locked");
+  __owns_ = __m_->try_lock();
+  return __owns_;
+}
+
+template <class _Mutex>
+template <class _Rep, class _Period>
+bool unique_lock<_Mutex>::try_lock_for(const chrono::duration<_Rep, _Period>& __d) {
+  if (__m_ == nullptr)
+    __throw_system_error(EPERM, "unique_lock::try_lock_for: references null mutex");
+  if (__owns_)
+    __throw_system_error(EDEADLK, "unique_lock::try_lock_for: already locked");
+  __owns_ = __m_->try_lock_for(__d);
+  return __owns_;
+}
+
+template <class _Mutex>
+template <class _Clock, class _Duration>
+bool unique_lock<_Mutex>::try_lock_until(const chrono::time_point<_Clock, _Duration>& __t) {
+  if (__m_ == nullptr)
+    __throw_system_error(EPERM, "unique_lock::try_lock_until: references null mutex");
+  if (__owns_)
+    __throw_system_error(EDEADLK, "unique_lock::try_lock_until: already locked");
+  __owns_ = __m_->try_lock_until(__t);
+  return __owns_;
+}
+
+template <class _Mutex>
+void unique_lock<_Mutex>::unlock() {
+  if (!__owns_)
+    __throw_system_error(EPERM, "unique_lock::unlock: not locked");
+  __m_->unlock();
+  __owns_ = false;
+}
+
+template <class _Mutex>
+inline _LIBCPP_HIDE_FROM_ABI void swap(unique_lock<_Mutex>& __x, unique_lock<_Mutex>& __y) _NOEXCEPT {
+  __x.swap(__y);
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_HAS_NO_THREADS
+
+#endif // _LIBCPP___MUTEX_UNIQUE_LOCK_H
diff --git a/libcxx/include/__mutex_base b/libcxx/include/__mutex_base
deleted file mode 100644
--- a/libcxx/include/__mutex_base
+++ /dev/null
@@ -1,525 +0,0 @@
-// -*- C++ -*-
-//===----------------------------------------------------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef _LIBCPP___MUTEX_BASE
-#define _LIBCPP___MUTEX_BASE
-
-#include <__chrono/duration.h>
-#include <__chrono/steady_clock.h>
-#include <__chrono/system_clock.h>
-#include <__chrono/time_point.h>
-#include <__config>
-#include <__threading_support>
-#include <__type_traits/is_floating_point.h>
-#include <__type_traits/is_nothrow_default_constructible.h>
-#include <ratio>
-#include <system_error>
-#include <time.h>
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#  pragma GCC system_header
-#endif
-
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-#ifndef _LIBCPP_HAS_NO_THREADS
-
-class _LIBCPP_TYPE_VIS _LIBCPP_THREAD_SAFETY_ANNOTATION(capability("mutex")) mutex
-{
-    __libcpp_mutex_t __m_ = _LIBCPP_MUTEX_INITIALIZER;
-
-public:
-    _LIBCPP_INLINE_VISIBILITY
-    _LIBCPP_CONSTEXPR mutex() = default;
-
-    mutex(const mutex&) = delete;
-    mutex& operator=(const mutex&) = delete;
-
-#if defined(_LIBCPP_HAS_TRIVIAL_MUTEX_DESTRUCTION)
-    ~mutex() = default;
-#else
-    ~mutex() _NOEXCEPT;
-#endif
-
-    void lock() _LIBCPP_THREAD_SAFETY_ANNOTATION(acquire_capability());
-    bool try_lock() _NOEXCEPT _LIBCPP_THREAD_SAFETY_ANNOTATION(try_acquire_capability(true));
-    void unlock() _NOEXCEPT _LIBCPP_THREAD_SAFETY_ANNOTATION(release_capability());
-
-    typedef __libcpp_mutex_t* native_handle_type;
-    _LIBCPP_INLINE_VISIBILITY native_handle_type native_handle() {return &__m_;}
-};
-
-static_assert(is_nothrow_default_constructible<mutex>::value,
-              "the default constructor for std::mutex must be nothrow");
-
-struct _LIBCPP_TYPE_VIS defer_lock_t { explicit defer_lock_t() = default; };
-struct _LIBCPP_TYPE_VIS try_to_lock_t { explicit try_to_lock_t() = default; };
-struct _LIBCPP_TYPE_VIS adopt_lock_t { explicit adopt_lock_t() = default; };
-
-#if defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_LIBRARY)
-
-extern _LIBCPP_EXPORTED_FROM_ABI const defer_lock_t  defer_lock;
-extern _LIBCPP_EXPORTED_FROM_ABI const try_to_lock_t try_to_lock;
-extern _LIBCPP_EXPORTED_FROM_ABI const adopt_lock_t  adopt_lock;
-
-#else
-
-/* inline */ constexpr defer_lock_t  defer_lock  = defer_lock_t();
-/* inline */ constexpr try_to_lock_t try_to_lock = try_to_lock_t();
-/* inline */ constexpr adopt_lock_t  adopt_lock  = adopt_lock_t();
-
-#endif
-
-template <class _Mutex>
-class _LIBCPP_TEMPLATE_VIS _LIBCPP_THREAD_SAFETY_ANNOTATION(scoped_lockable)
-lock_guard
-{
-public:
-    typedef _Mutex mutex_type;
-
-private:
-    mutex_type& __m_;
-public:
-
-    _LIBCPP_NODISCARD_EXT _LIBCPP_INLINE_VISIBILITY
-    explicit lock_guard(mutex_type& __m) _LIBCPP_THREAD_SAFETY_ANNOTATION(acquire_capability(__m))
-        : __m_(__m) {__m_.lock();}
-
-    _LIBCPP_NODISCARD_EXT _LIBCPP_INLINE_VISIBILITY
-    lock_guard(mutex_type& __m, adopt_lock_t) _LIBCPP_THREAD_SAFETY_ANNOTATION(requires_capability(__m))
-        : __m_(__m) {}
-    _LIBCPP_INLINE_VISIBILITY
-    ~lock_guard() _LIBCPP_THREAD_SAFETY_ANNOTATION(release_capability()) {__m_.unlock();}
-
-private:
-    lock_guard(lock_guard const&) = delete;
-    lock_guard& operator=(lock_guard const&) = delete;
-};
-_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(lock_guard);
-
-template <class _Mutex>
-class _LIBCPP_TEMPLATE_VIS unique_lock
-{
-public:
-    typedef _Mutex mutex_type;
-
-private:
-    mutex_type* __m_;
-    bool __owns_;
-
-public:
-    _LIBCPP_INLINE_VISIBILITY
-    unique_lock() _NOEXCEPT : __m_(nullptr), __owns_(false) {}
-    _LIBCPP_INLINE_VISIBILITY
-    explicit unique_lock(mutex_type& __m)
-        : __m_(_VSTD::addressof(__m)), __owns_(true) {__m_->lock();}
-    _LIBCPP_INLINE_VISIBILITY
-    unique_lock(mutex_type& __m, defer_lock_t) _NOEXCEPT
-        : __m_(_VSTD::addressof(__m)), __owns_(false) {}
-    _LIBCPP_INLINE_VISIBILITY
-    unique_lock(mutex_type& __m, try_to_lock_t)
-        : __m_(_VSTD::addressof(__m)), __owns_(__m.try_lock()) {}
-    _LIBCPP_INLINE_VISIBILITY
-    unique_lock(mutex_type& __m, adopt_lock_t)
-        : __m_(_VSTD::addressof(__m)), __owns_(true) {}
-    template <class _Clock, class _Duration>
-    _LIBCPP_INLINE_VISIBILITY
-        unique_lock(mutex_type& __m, const chrono::time_point<_Clock, _Duration>& __t)
-            : __m_(_VSTD::addressof(__m)), __owns_(__m.try_lock_until(__t)) {}
-    template <class _Rep, class _Period>
-    _LIBCPP_INLINE_VISIBILITY
-        unique_lock(mutex_type& __m, const chrono::duration<_Rep, _Period>& __d)
-            : __m_(_VSTD::addressof(__m)), __owns_(__m.try_lock_for(__d)) {}
-    _LIBCPP_INLINE_VISIBILITY
-    ~unique_lock()
-    {
-        if (__owns_)
-            __m_->unlock();
-    }
-
-    unique_lock(unique_lock const&) = delete;
-    unique_lock& operator=(unique_lock const&) = delete;
-
-    _LIBCPP_INLINE_VISIBILITY
-    unique_lock(unique_lock&& __u) _NOEXCEPT
-        : __m_(__u.__m_), __owns_(__u.__owns_)
-        {__u.__m_ = nullptr; __u.__owns_ = false;}
-    _LIBCPP_INLINE_VISIBILITY
-    unique_lock& operator=(unique_lock&& __u) _NOEXCEPT
-        {
-            if (__owns_)
-                __m_->unlock();
-            __m_ = __u.__m_;
-            __owns_ = __u.__owns_;
-            __u.__m_ = nullptr;
-            __u.__owns_ = false;
-            return *this;
-        }
-
-    void lock();
-    bool try_lock();
-
-    template <class _Rep, class _Period>
-        bool try_lock_for(const chrono::duration<_Rep, _Period>& __d);
-    template <class _Clock, class _Duration>
-        bool try_lock_until(const chrono::time_point<_Clock, _Duration>& __t);
-
-    void unlock();
-
-    _LIBCPP_INLINE_VISIBILITY
-    void swap(unique_lock& __u) _NOEXCEPT
-    {
-        _VSTD::swap(__m_, __u.__m_);
-        _VSTD::swap(__owns_, __u.__owns_);
-    }
-    _LIBCPP_INLINE_VISIBILITY
-    mutex_type* release() _NOEXCEPT
-    {
-        mutex_type* __m = __m_;
-        __m_ = nullptr;
-        __owns_ = false;
-        return __m;
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    bool owns_lock() const _NOEXCEPT {return __owns_;}
-    _LIBCPP_INLINE_VISIBILITY
-    explicit operator bool() const _NOEXCEPT {return __owns_;}
-    _LIBCPP_INLINE_VISIBILITY
-    mutex_type* mutex() const _NOEXCEPT {return __m_;}
-};
-_LIBCPP_CTAD_SUPPORTED_FOR_TYPE(unique_lock);
-
-template <class _Mutex>
-void
-unique_lock<_Mutex>::lock()
-{
-    if (__m_ == nullptr)
-        __throw_system_error(EPERM, "unique_lock::lock: references null mutex");
-    if (__owns_)
-        __throw_system_error(EDEADLK, "unique_lock::lock: already locked");
-    __m_->lock();
-    __owns_ = true;
-}
-
-template <class _Mutex>
-bool
-unique_lock<_Mutex>::try_lock()
-{
-    if (__m_ == nullptr)
-        __throw_system_error(EPERM, "unique_lock::try_lock: references null mutex");
-    if (__owns_)
-        __throw_system_error(EDEADLK, "unique_lock::try_lock: already locked");
-    __owns_ = __m_->try_lock();
-    return __owns_;
-}
-
-template <class _Mutex>
-template <class _Rep, class _Period>
-bool
-unique_lock<_Mutex>::try_lock_for(const chrono::duration<_Rep, _Period>& __d)
-{
-    if (__m_ == nullptr)
-        __throw_system_error(EPERM, "unique_lock::try_lock_for: references null mutex");
-    if (__owns_)
-        __throw_system_error(EDEADLK, "unique_lock::try_lock_for: already locked");
-    __owns_ = __m_->try_lock_for(__d);
-    return __owns_;
-}
-
-template <class _Mutex>
-template <class _Clock, class _Duration>
-bool
-unique_lock<_Mutex>::try_lock_until(const chrono::time_point<_Clock, _Duration>& __t)
-{
-    if (__m_ == nullptr)
-        __throw_system_error(EPERM, "unique_lock::try_lock_until: references null mutex");
-    if (__owns_)
-        __throw_system_error(EDEADLK, "unique_lock::try_lock_until: already locked");
-    __owns_ = __m_->try_lock_until(__t);
-    return __owns_;
-}
-
-template <class _Mutex>
-void
-unique_lock<_Mutex>::unlock()
-{
-    if (!__owns_)
-        __throw_system_error(EPERM, "unique_lock::unlock: not locked");
-    __m_->unlock();
-    __owns_ = false;
-}
-
-template <class _Mutex>
-inline _LIBCPP_INLINE_VISIBILITY
-void
-swap(unique_lock<_Mutex>& __x, unique_lock<_Mutex>& __y) _NOEXCEPT
-    {__x.swap(__y);}
-
-//enum class cv_status
-_LIBCPP_DECLARE_STRONG_ENUM(cv_status)
-{
-    no_timeout,
-    timeout
-};
-_LIBCPP_DECLARE_STRONG_ENUM_EPILOG(cv_status)
-
-class _LIBCPP_TYPE_VIS condition_variable
-{
-    __libcpp_condvar_t __cv_ = _LIBCPP_CONDVAR_INITIALIZER;
-public:
-    _LIBCPP_INLINE_VISIBILITY
-    _LIBCPP_CONSTEXPR condition_variable() _NOEXCEPT = default;
-
-#ifdef _LIBCPP_HAS_TRIVIAL_CONDVAR_DESTRUCTION
-    ~condition_variable() = default;
-#else
-    ~condition_variable();
-#endif
-
-    condition_variable(const condition_variable&) = delete;
-    condition_variable& operator=(const condition_variable&) = delete;
-
-    void notify_one() _NOEXCEPT;
-    void notify_all() _NOEXCEPT;
-
-    void wait(unique_lock<mutex>& __lk) _NOEXCEPT;
-    template <class _Predicate>
-        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
-        void wait(unique_lock<mutex>& __lk, _Predicate __pred);
-
-    template <class _Clock, class _Duration>
-        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
-        cv_status
-        wait_until(unique_lock<mutex>& __lk,
-                   const chrono::time_point<_Clock, _Duration>& __t);
-
-    template <class _Clock, class _Duration, class _Predicate>
-        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
-        bool
-        wait_until(unique_lock<mutex>& __lk,
-                   const chrono::time_point<_Clock, _Duration>& __t,
-                   _Predicate __pred);
-
-    template <class _Rep, class _Period>
-        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
-        cv_status
-        wait_for(unique_lock<mutex>& __lk,
-                 const chrono::duration<_Rep, _Period>& __d);
-
-    template <class _Rep, class _Period, class _Predicate>
-        bool
-        _LIBCPP_INLINE_VISIBILITY
-        wait_for(unique_lock<mutex>& __lk,
-                 const chrono::duration<_Rep, _Period>& __d,
-                 _Predicate __pred);
-
-    typedef __libcpp_condvar_t* native_handle_type;
-    _LIBCPP_INLINE_VISIBILITY native_handle_type native_handle() {return &__cv_;}
-
-private:
-    void __do_timed_wait(unique_lock<mutex>& __lk,
-       chrono::time_point<chrono::system_clock, chrono::nanoseconds>) _NOEXCEPT;
-#if defined(_LIBCPP_HAS_COND_CLOCKWAIT)
-    void __do_timed_wait(unique_lock<mutex>& __lk,
-       chrono::time_point<chrono::steady_clock, chrono::nanoseconds>) _NOEXCEPT;
-#endif
-    template <class _Clock>
-    void __do_timed_wait(unique_lock<mutex>& __lk,
-       chrono::time_point<_Clock, chrono::nanoseconds>) _NOEXCEPT;
-};
-#endif // !_LIBCPP_HAS_NO_THREADS
-
-template <class _Rep, class _Period>
-inline _LIBCPP_INLINE_VISIBILITY
-__enable_if_t<is_floating_point<_Rep>::value, chrono::nanoseconds>
-__safe_nanosecond_cast(chrono::duration<_Rep, _Period> __d)
-{
-    using namespace chrono;
-    using __ratio = ratio_divide<_Period, nano>;
-    using __ns_rep = nanoseconds::rep;
-    _Rep __result_float = __d.count() * __ratio::num / __ratio::den;
-
-    _Rep __result_max = numeric_limits<__ns_rep>::max();
-    if (__result_float >= __result_max) {
-        return nanoseconds::max();
-    }
-
-    _Rep __result_min = numeric_limits<__ns_rep>::min();
-    if (__result_float <= __result_min) {
-        return nanoseconds::min();
-    }
-
-    return nanoseconds(static_cast<__ns_rep>(__result_float));
-}
-
-template <class _Rep, class _Period>
-inline _LIBCPP_INLINE_VISIBILITY
-__enable_if_t<!is_floating_point<_Rep>::value, chrono::nanoseconds>
-__safe_nanosecond_cast(chrono::duration<_Rep, _Period> __d)
-{
-    using namespace chrono;
-    if (__d.count() == 0) {
-        return nanoseconds(0);
-    }
-
-    using __ratio = ratio_divide<_Period, nano>;
-    using __ns_rep = nanoseconds::rep;
-    __ns_rep __result_max = numeric_limits<__ns_rep>::max();
-    if (__d.count() > 0 && __d.count() > __result_max / __ratio::num) {
-        return nanoseconds::max();
-    }
-
-    __ns_rep __result_min = numeric_limits<__ns_rep>::min();
-    if (__d.count() < 0 && __d.count() < __result_min / __ratio::num) {
-        return nanoseconds::min();
-    }
-
-    __ns_rep __result = __d.count() * __ratio::num / __ratio::den;
-    if (__result == 0) {
-        return nanoseconds(1);
-    }
-
-    return nanoseconds(__result);
-}
-
-#ifndef _LIBCPP_HAS_NO_THREADS
-template <class _Predicate>
-void
-condition_variable::wait(unique_lock<mutex>& __lk, _Predicate __pred)
-{
-    while (!__pred())
-        wait(__lk);
-}
-
-template <class _Clock, class _Duration>
-cv_status
-condition_variable::wait_until(unique_lock<mutex>& __lk,
-                               const chrono::time_point<_Clock, _Duration>& __t)
-{
-    using namespace chrono;
-    using __clock_tp_ns = time_point<_Clock, nanoseconds>;
-
-    typename _Clock::time_point __now = _Clock::now();
-    if (__t <= __now)
-        return cv_status::timeout;
-
-    __clock_tp_ns __t_ns = __clock_tp_ns(_VSTD::__safe_nanosecond_cast(__t.time_since_epoch()));
-
-    __do_timed_wait(__lk, __t_ns);
-    return _Clock::now() < __t ? cv_status::no_timeout : cv_status::timeout;
-}
-
-template <class _Clock, class _Duration, class _Predicate>
-bool
-condition_variable::wait_until(unique_lock<mutex>& __lk,
-                   const chrono::time_point<_Clock, _Duration>& __t,
-                   _Predicate __pred)
-{
-    while (!__pred())
-    {
-        if (wait_until(__lk, __t) == cv_status::timeout)
-            return __pred();
-    }
-    return true;
-}
-
-template <class _Rep, class _Period>
-cv_status
-condition_variable::wait_for(unique_lock<mutex>& __lk,
-                             const chrono::duration<_Rep, _Period>& __d)
-{
-    using namespace chrono;
-    if (__d <= __d.zero())
-        return cv_status::timeout;
-    using __ns_rep = nanoseconds::rep;
-    steady_clock::time_point __c_now = steady_clock::now();
-
-#if defined(_LIBCPP_HAS_COND_CLOCKWAIT)
-    using __clock_tp_ns = time_point<steady_clock, nanoseconds>;
-    __ns_rep __now_count_ns = _VSTD::__safe_nanosecond_cast(__c_now.time_since_epoch()).count();
-#else
-    using __clock_tp_ns = time_point<system_clock, nanoseconds>;
-    __ns_rep __now_count_ns = _VSTD::__safe_nanosecond_cast(system_clock::now().time_since_epoch()).count();
-#endif
-
-    __ns_rep __d_ns_count = _VSTD::__safe_nanosecond_cast(__d).count();
-
-    if (__now_count_ns > numeric_limits<__ns_rep>::max() - __d_ns_count) {
-        __do_timed_wait(__lk, __clock_tp_ns::max());
-    } else {
-        __do_timed_wait(__lk, __clock_tp_ns(nanoseconds(__now_count_ns + __d_ns_count)));
-    }
-
-    return steady_clock::now() - __c_now < __d ? cv_status::no_timeout :
-                                                 cv_status::timeout;
-}
-
-template <class _Rep, class _Period, class _Predicate>
-inline
-bool
-condition_variable::wait_for(unique_lock<mutex>& __lk,
-                             const chrono::duration<_Rep, _Period>& __d,
-                             _Predicate __pred)
-{
-    return wait_until(__lk, chrono::steady_clock::now() + __d,
-                      _VSTD::move(__pred));
-}
-
-#if defined(_LIBCPP_HAS_COND_CLOCKWAIT)
-inline
-void
-condition_variable::__do_timed_wait(unique_lock<mutex>& __lk,
-     chrono::time_point<chrono::steady_clock, chrono::nanoseconds> __tp) _NOEXCEPT
-{
-    using namespace chrono;
-    if (!__lk.owns_lock())
-        __throw_system_error(EPERM,
-                            "condition_variable::timed wait: mutex not locked");
-    nanoseconds __d = __tp.time_since_epoch();
-    timespec __ts;
-    seconds __s = duration_cast<seconds>(__d);
-    using __ts_sec = decltype(__ts.tv_sec);
-    const __ts_sec __ts_sec_max = numeric_limits<__ts_sec>::max();
-    if (__s.count() < __ts_sec_max)
-    {
-        __ts.tv_sec = static_cast<__ts_sec>(__s.count());
-        __ts.tv_nsec = (__d - __s).count();
-    }
-    else
-    {
-        __ts.tv_sec = __ts_sec_max;
-        __ts.tv_nsec = giga::num - 1;
-    }
-    int __ec = pthread_cond_clockwait(&__cv_, __lk.mutex()->native_handle(), CLOCK_MONOTONIC, &__ts);
-    if (__ec != 0 && __ec != ETIMEDOUT)
-        __throw_system_error(__ec, "condition_variable timed_wait failed");
-}
-#endif // _LIBCPP_HAS_COND_CLOCKWAIT
-
-template <class _Clock>
-inline
-void
-condition_variable::__do_timed_wait(unique_lock<mutex>& __lk,
-     chrono::time_point<_Clock, chrono::nanoseconds> __tp) _NOEXCEPT
-{
-    wait_for(__lk, __tp - _Clock::now());
-}
-
-#endif // !_LIBCPP_HAS_NO_THREADS
-
-_LIBCPP_END_NAMESPACE_STD
-
-_LIBCPP_POP_MACROS
-
-#endif // _LIBCPP___MUTEX_BASE
diff --git a/libcxx/include/condition_variable b/libcxx/include/condition_variable
--- a/libcxx/include/condition_variable
+++ b/libcxx/include/condition_variable
@@ -107,10 +107,18 @@
 */
 
 #include <__assert> // all public C++ headers provide the assertion handler
+#include <__chrono/duration.h>
+#include <__chrono/steady_clock.h>
+#include <__chrono/time_point.h>
+#include <__condition_variable/condition_variable.h>
 #include <__config>
 #include <__memory/shared_ptr.h>
 #include <__memory/unique_ptr.h>
-#include <__mutex_base>
+#include <__mutex/lock_guard.h>
+#include <__mutex/mutex.h>
+#include <__mutex/tag_types.h>
+#include <__mutex/unique_lock.h>
+#include <__utility/move.h>
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -271,7 +279,14 @@
 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
 #  include <atomic>
 #  include <concepts>
+#  include <cstdint>
+#  include <cstdlib>
+#  include <cstring>
+#  include <initializer_list>
+#  include <new>
+#  include <stdexcept>
 #  include <type_traits>
+#  include <typeinfo>
 #endif
 
 #endif // _LIBCPP_CONDITION_VARIABLE
diff --git a/libcxx/include/libcxx.imp b/libcxx/include/libcxx.imp
--- a/libcxx/include/libcxx.imp
+++ b/libcxx/include/libcxx.imp
@@ -22,6 +22,7 @@
   { include: [ "@<__chrono/.*>", "private", "<chrono>", "public" ] },
   { include: [ "@<__compare/.*>", "private", "<compare>", "public" ] },
   { include: [ "@<__concepts/.*>", "private", "<concepts>", "public" ] },
+  { include: [ "@<__condition_variable/.*>", "private", "<condition_variable>", "public" ] },
   { include: [ "@<__coroutine/.*>", "private", "<coroutine>", "public" ] },
   { include: [ "@<__debug_utils/.*>", "private", "<debug_utils>", "public" ] },
   { include: [ "@<__exception/.*>", "private", "<exception>", "public" ] },
@@ -34,6 +35,7 @@
   { include: [ "@<__iterator/.*>", "private", "<iterator>", "public" ] },
   { include: [ "@<__memory/.*>", "private", "<memory>", "public" ] },
   { include: [ "@<__memory_resource/.*>", "private", "<memory_resource>", "public" ] },
+  { include: [ "@<__mutex/.*>", "private", "<mutex>", "public" ] },
   { include: [ "@<__numeric/.*>", "private", "<numeric>", "public" ] },
   { include: [ "@<__random/.*>", "private", "<random>", "public" ] },
   { include: [ "@<__ranges/.*>", "private", "<ranges>", "public" ] },
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -813,6 +813,10 @@
   module condition_variable {
     header "condition_variable"
     export *
+
+    module __condition_variable {
+      module condition_variable { private header "__condition_variable/condition_variable.h" }
+    }
   }
   module coroutine {
     header "coroutine"
@@ -1174,6 +1178,13 @@
     @requires_LIBCXX_ENABLE_THREADS@
     header "mutex"
     export *
+
+    module __mutex {
+      module lock_guard  { private header "__mutex/lock_guard.h" }
+      module mutex       { private header "__mutex/mutex.h" }
+      module tag_types   { private header "__mutex/tag_types.h" }
+      module unique_lock { private header "__mutex/unique_lock.h" }
+    }
   }
   module new {
     header "new"
@@ -1695,7 +1706,6 @@
     private header "__locale" export *
   }
   module __mbstate_t         { private header "__mbstate_t.h"       export * }
-  module __mutex_base        { private header "__mutex_base"        export * }
   module __node_handle       { private header "__node_handle"       export * }
   module __split_buffer      { private header "__split_buffer"      export * }
   module __std_stream        {
diff --git a/libcxx/include/mutex b/libcxx/include/mutex
--- a/libcxx/include/mutex
+++ b/libcxx/include/mutex
@@ -187,9 +187,15 @@
 */
 
 #include <__assert> // all public C++ headers provide the assertion handler
+#include <__chrono/time_point.h>
+#include <__chrono/steady_clock.h>
+#include <__condition_variable/condition_variable.h>
 #include <__config>
 #include <__memory/shared_ptr.h>
-#include <__mutex_base>
+#include <__mutex/lock_guard.h>
+#include <__mutex/mutex.h>
+#include <__mutex/tag_types.h>
+#include <__mutex/unique_lock.h>
 #include <__threading_support>
 #include <__utility/forward.h>
 #include <cstdint>
@@ -706,9 +712,15 @@
 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
 #  include <atomic>
 #  include <concepts>
+#  include <cstdlib>
+#  include <cstring>
 #  include <ctime>
 #  include <functional>
+#  include <initializer_list>
+#  include <new>
+#  include <stdexcept>
 #  include <type_traits>
+#  include <typeinfo>
 #endif
 
 #endif // _LIBCPP_MUTEX
diff --git a/libcxx/include/shared_mutex b/libcxx/include/shared_mutex
--- a/libcxx/include/shared_mutex
+++ b/libcxx/include/shared_mutex
@@ -124,7 +124,19 @@
 
 #include <__assert> // all public C++ headers provide the assertion handler
 #include <__availability>
+#include <__chrono/duration.h>
+#include <__chrono/ostream.h>
+#include <__chrono/steady_clock.h>
+#include <__chrono/time_point.h>
+#include <__condition_variable/condition_variable.h>
 #include <__config>
+#include <__memory/addressof.h>
+#include <__mutex/mutex.h>
+#include <__mutex/tag_types.h>
+#include <__mutex/unique_lock.h>
+#include <__utility/swap.h>
+#include <cerrno>
+#include <system_error>
 #include <version>
 
 _LIBCPP_PUSH_MACROS
@@ -133,8 +145,6 @@
 
 #if _LIBCPP_STD_VER >= 14 || defined(_LIBCPP_BUILDING_LIBRARY)
 
-#include <__mutex_base>
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
diff --git a/libcxx/include/thread b/libcxx/include/thread
--- a/libcxx/include/thread
+++ b/libcxx/include/thread
@@ -84,12 +84,16 @@
 */
 
 #include <__assert> // all public C++ headers provide the assertion handler
+#include <__chrono/steady_clock.h>
+#include <__chrono/time_point.h>
+#include <__condition_variable/condition_variable.h>
 #include <__config>
 #include <__exception/terminate.h>
 #include <__functional/hash.h>
 #include <__memory/addressof.h>
 #include <__memory/unique_ptr.h>
-#include <__mutex_base>
+#include <__mutex/mutex.h>
+#include <__mutex/unique_lock.h>
 #include <__thread/poll_with_backoff.h>
 #include <__thread/timed_backoff_policy.h>
 #include <__threading_support>
@@ -416,7 +420,10 @@
 #endif
 
 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
+#  include <cstdint>
+#  include <cstring>
 #  include <functional>
+#  include <new>
 #endif
 
 #endif // _LIBCPP_THREAD
diff --git a/libcxx/src/shared_mutex.cpp b/libcxx/src/shared_mutex.cpp
--- a/libcxx/src/shared_mutex.cpp
+++ b/libcxx/src/shared_mutex.cpp
@@ -10,6 +10,7 @@
 
 #ifndef _LIBCPP_HAS_NO_THREADS
 
+#include <mutex>
 #include <shared_mutex>
 #if defined(__ELF__) && defined(_LIBCPP_LINK_PTHREAD_LIB)
 #  pragma comment(lib, "pthread")
diff --git a/libcxx/test/libcxx/private_headers.verify.cpp b/libcxx/test/libcxx/private_headers.verify.cpp
--- a/libcxx/test/libcxx/private_headers.verify.cpp
+++ b/libcxx/test/libcxx/private_headers.verify.cpp
@@ -328,6 +328,7 @@
 #include <__concepts/semiregular.h> // expected-error@*:* {{use of private header from outside its module: '__concepts/semiregular.h'}}
 #include <__concepts/swappable.h> // expected-error@*:* {{use of private header from outside its module: '__concepts/swappable.h'}}
 #include <__concepts/totally_ordered.h> // expected-error@*:* {{use of private header from outside its module: '__concepts/totally_ordered.h'}}
+#include <__condition_variable/condition_variable.h> // expected-error@*:* {{use of private header from outside its module: '__condition_variable/condition_variable.h'}}
 #include <__coroutine/coroutine_handle.h> // expected-error@*:* {{use of private header from outside its module: '__coroutine/coroutine_handle.h'}}
 #include <__coroutine/coroutine_traits.h> // expected-error@*:* {{use of private header from outside its module: '__coroutine/coroutine_traits.h'}}
 #include <__coroutine/noop_coroutine_handle.h> // expected-error@*:* {{use of private header from outside its module: '__coroutine/noop_coroutine_handle.h'}}
@@ -505,7 +506,10 @@
 #include <__memory_resource/pool_options.h> // expected-error@*:* {{use of private header from outside its module: '__memory_resource/pool_options.h'}}
 #include <__memory_resource/synchronized_pool_resource.h> // expected-error@*:* {{use of private header from outside its module: '__memory_resource/synchronized_pool_resource.h'}}
 #include <__memory_resource/unsynchronized_pool_resource.h> // expected-error@*:* {{use of private header from outside its module: '__memory_resource/unsynchronized_pool_resource.h'}}
-#include <__mutex_base> // expected-error@*:* {{use of private header from outside its module: '__mutex_base'}}
+#include <__mutex/lock_guard.h> // expected-error@*:* {{use of private header from outside its module: '__mutex/lock_guard.h'}}
+#include <__mutex/mutex.h> // expected-error@*:* {{use of private header from outside its module: '__mutex/mutex.h'}}
+#include <__mutex/tag_types.h> // expected-error@*:* {{use of private header from outside its module: '__mutex/tag_types.h'}}
+#include <__mutex/unique_lock.h> // expected-error@*:* {{use of private header from outside its module: '__mutex/unique_lock.h'}}
 #include <__node_handle> // expected-error@*:* {{use of private header from outside its module: '__node_handle'}}
 #include <__numeric/accumulate.h> // expected-error@*:* {{use of private header from outside its module: '__numeric/accumulate.h'}}
 #include <__numeric/adjacent_difference.h> // expected-error@*:* {{use of private header from outside its module: '__numeric/adjacent_difference.h'}}
diff --git a/libcxx/test/libcxx/thread/thread.condition/thread.condition.condvar/native_handle.pass.cpp b/libcxx/test/libcxx/thread/thread.condition/thread.condition.condvar/native_handle.pass.cpp
--- a/libcxx/test/libcxx/thread/thread.condition/thread.condition.condvar/native_handle.pass.cpp
+++ b/libcxx/test/libcxx/thread/thread.condition/thread.condition.condvar/native_handle.pass.cpp
@@ -17,8 +17,10 @@
 // typedef pthread_cond_t* native_handle_type;
 // native_handle_type native_handle();
 
-#include <condition_variable>
 #include <cassert>
+#include <condition_variable>
+#include <pthread.h>
+#include <type_traits>
 
 #include "test_macros.h"
 
diff --git a/libcxx/test/libcxx/transitive_includes/cxx2b.csv b/libcxx/test/libcxx/transitive_includes/cxx2b.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx2b.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx2b.csv
@@ -110,11 +110,14 @@
 concepts cstddef
 concepts version
 condition_variable cstddef
-condition_variable cstdint
 condition_variable cstdlib
+<<<<<<< HEAD
 condition_variable cstring
 condition_variable ctime
 condition_variable initializer_list
+=======
+condition_variable ctime
+>>>>>>> f626323c3b1a ([libc++] Granularize __mutex_base)
 condition_variable iosfwd
 condition_variable limits
 condition_variable new
@@ -403,9 +406,13 @@
 mutex cstddef
 mutex cstdint
 mutex cstdlib
+<<<<<<< HEAD
 mutex cstring
 mutex ctime
 mutex initializer_list
+=======
+mutex ctime
+>>>>>>> f626323c3b1a ([libc++] Granularize __mutex_base)
 mutex iosfwd
 mutex limits
 mutex new
@@ -591,12 +598,9 @@
 system_error version
 thread compare
 thread cstddef
-thread cstdint
-thread cstring
 thread ctime
 thread iosfwd
 thread limits
-thread new
 thread ratio
 thread system_error
 thread tuple
diff --git a/libcxx/test/std/thread/futures/futures.shared_future/wait.pass.cpp b/libcxx/test/std/thread/futures/futures.shared_future/wait.pass.cpp
--- a/libcxx/test/std/thread/futures/futures.shared_future/wait.pass.cpp
+++ b/libcxx/test/std/thread/futures/futures.shared_future/wait.pass.cpp
@@ -18,6 +18,7 @@
 #include <cassert>
 #include <chrono>
 #include <future>
+#include <ratio>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/futures/futures.unique_future/wait.pass.cpp b/libcxx/test/std/thread/futures/futures.unique_future/wait.pass.cpp
--- a/libcxx/test/std/thread/futures/futures.unique_future/wait.pass.cpp
+++ b/libcxx/test/std/thread/futures/futures.unique_future/wait.pass.cpp
@@ -18,6 +18,7 @@
 #include <cassert>
 #include <chrono>
 #include <future>
+#include <ratio>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.cons/mutex.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.cons/mutex.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.cons/mutex.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.cons/mutex.pass.cpp
@@ -22,11 +22,12 @@
 // template<class _Mutex> shared_lock(shared_lock<_Mutex>)
 //     -> shared_lock<_Mutex>;  // C++17
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <shared_mutex>
 #include <thread>
 #include <vector>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.cons/mutex_try_to_lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.cons/mutex_try_to_lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.cons/mutex_try_to_lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.cons/mutex_try_to_lock.pass.cpp
@@ -19,11 +19,13 @@
 
 // shared_lock(mutex_type& m, try_to_lock_t);
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
+#include <mutex>
 #include <shared_mutex>
 #include <thread>
 #include <vector>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/lock.pass.cpp
@@ -19,11 +19,13 @@
 
 // void lock();
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
+#include <mutex>
 #include <shared_mutex>
 #include <thread>
 #include <vector>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/try_lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/try_lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/try_lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/try_lock.pass.cpp
@@ -17,9 +17,10 @@
 
 // bool try_lock();
 
-#include <shared_mutex>
 #include <cassert>
 #include <mutex>
+#include <shared_mutex>
+#include <system_error>
 
 #include "test_macros.h"
 
diff --git a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/try_lock_for.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/try_lock_for.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/try_lock_for.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/try_lock_for.pass.cpp
@@ -16,10 +16,11 @@
 // template <class Rep, class Period>
 //   bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
 
-#include <shared_mutex>
 #include <cassert>
 #include <chrono>
 #include <mutex>
+#include <shared_mutex>
+#include <system_error>
 
 #include "test_macros.h"
 
diff --git a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/try_lock_until.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/try_lock_until.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/try_lock_until.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.shared/thread.lock.shared.locking/try_lock_until.pass.cpp
@@ -16,10 +16,11 @@
 // template <class Clock, class Duration>
 //   bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
 
-#include <shared_mutex>
 #include <cassert>
 #include <chrono>
 #include <mutex>
+#include <shared_mutex>
+#include <system_error>
 
 #include "test_macros.h"
 
diff --git a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.cons/mutex.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.cons/mutex.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.cons/mutex.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.cons/mutex.pass.cpp
@@ -18,10 +18,11 @@
 // template<class _Mutex> unique_lock(unique_lock<_Mutex>)
 //     -> unique_lock<_Mutex>;  // C++17
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <mutex>
 #include <thread>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.cons/mutex_try_to_lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.cons/mutex_try_to_lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.cons/mutex_try_to_lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.cons/mutex_try_to_lock.pass.cpp
@@ -15,10 +15,11 @@
 
 // unique_lock(mutex_type& m, try_to_lock_t);
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <mutex>
 #include <thread>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/lock.pass.cpp
@@ -15,10 +15,11 @@
 
 // void lock();
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <mutex>
 #include <thread>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/try_lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/try_lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/try_lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/try_lock.pass.cpp
@@ -16,8 +16,9 @@
 
 // bool try_lock();
 
-#include <mutex>
 #include <cassert>
+#include <mutex>
+#include <system_error>
 
 #include "test_macros.h"
 
diff --git a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/try_lock_for.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/try_lock_for.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/try_lock_for.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/try_lock_for.pass.cpp
@@ -15,8 +15,9 @@
 // template <class Rep, class Period>
 //   bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
 
-#include <mutex>
 #include <cassert>
+#include <mutex>
+#include <system_error>
 
 #include "test_macros.h"
 
diff --git a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/try_lock_until.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/try_lock_until.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/try_lock_until.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/try_lock_until.pass.cpp
@@ -15,8 +15,9 @@
 // template <class Clock, class Duration>
 //   bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
 
-#include <mutex>
 #include <cassert>
+#include <mutex>
+#include <system_error>
 
 #include "test_macros.h"
 
diff --git a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/unlock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/unlock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/unlock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.lock/thread.lock.unique/thread.lock.unique.locking/unlock.pass.cpp
@@ -14,8 +14,9 @@
 
 // void unlock();
 
-#include <mutex>
 #include <cassert>
+#include <mutex>
+#include <system_error>
 
 #include "test_macros.h"
 
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/lock.pass.cpp
@@ -15,10 +15,11 @@
 
 // void lock();
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <mutex>
 #include <thread>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/try_lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/try_lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/try_lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/try_lock.pass.cpp
@@ -15,10 +15,11 @@
 
 // bool try_lock();
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <mutex>
 #include <thread>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/lock.pass.cpp
@@ -15,10 +15,11 @@
 
 // void lock();
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <mutex>
 #include <thread>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/try_lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/try_lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/try_lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/try_lock.pass.cpp
@@ -15,10 +15,11 @@
 
 // bool try_lock();
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <mutex>
 #include <thread>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/lock.pass.cpp
@@ -20,10 +20,11 @@
 
 // void lock();
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <shared_mutex>
 #include <thread>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/lock_shared.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/lock_shared.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/lock_shared.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/lock_shared.pass.cpp
@@ -20,11 +20,12 @@
 
 // void lock_shared();
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <shared_mutex>
 #include <thread>
 #include <vector>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/try_lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/try_lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/try_lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/try_lock.pass.cpp
@@ -20,10 +20,11 @@
 
 // bool try_lock();
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <shared_mutex>
 #include <thread>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/try_lock_shared.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/try_lock_shared.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/try_lock_shared.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.shared_mutex.requirements/thread.shared_mutex.class/try_lock_shared.pass.cpp
@@ -20,11 +20,12 @@
 
 // bool try_lock_shared();
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <shared_mutex>
 #include <thread>
 #include <vector>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/lock.pass.cpp
@@ -20,12 +20,12 @@
 
 // void lock();
 
-#include <thread>
-
 #include <atomic>
-#include <cstdlib>
 #include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <shared_mutex>
+#include <thread>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/lock_shared.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/lock_shared.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/lock_shared.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/lock_shared.pass.cpp
@@ -20,12 +20,13 @@
 
 // void lock_shared();
 
-#include <thread>
 
 #include <atomic>
 #include <cassert>
+#include <chrono>
 #include <cstdlib>
 #include <shared_mutex>
+#include <thread>
 #include <vector>
 
 #include "make_test_thread.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/try_lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/try_lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/try_lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/try_lock.pass.cpp
@@ -20,10 +20,11 @@
 
 // bool try_lock();
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <shared_mutex>
 #include <thread>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/try_lock_shared.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/try_lock_shared.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/try_lock_shared.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.sharedtimedmutex.requirements/thread.sharedtimedmutex.class/try_lock_shared.pass.cpp
@@ -20,11 +20,12 @@
 
 // bool try_lock_shared();
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <shared_mutex>
 #include <thread>
 #include <vector>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.class/lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.class/lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.class/lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.class/lock.pass.cpp
@@ -15,10 +15,11 @@
 
 // void lock();
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <mutex>
 #include <thread>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.class/try_lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.class/try_lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.class/try_lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.class/try_lock.pass.cpp
@@ -15,10 +15,11 @@
 
 // bool try_lock();
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <mutex>
 #include <thread>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.recursive/lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.recursive/lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.recursive/lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.recursive/lock.pass.cpp
@@ -15,10 +15,11 @@
 
 // void lock();
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <mutex>
 #include <thread>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.recursive/try_lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.recursive/try_lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.recursive/try_lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.mutex.requirements/thread.timedmutex.requirements/thread.timedmutex.recursive/try_lock.pass.cpp
@@ -15,10 +15,11 @@
 
 // bool try_lock();
 
+#include <cassert>
+#include <chrono>
+#include <cstdlib>
 #include <mutex>
 #include <thread>
-#include <cstdlib>
-#include <cassert>
 
 #include "make_test_thread.h"
 #include "test_macros.h"
diff --git a/libcxx/test/std/thread/thread.threads/thread.thread.this/sleep_until.pass.cpp b/libcxx/test/std/thread/thread.threads/thread.thread.this/sleep_until.pass.cpp
--- a/libcxx/test/std/thread/thread.threads/thread.thread.this/sleep_until.pass.cpp
+++ b/libcxx/test/std/thread/thread.threads/thread.thread.this/sleep_until.pass.cpp
@@ -13,9 +13,10 @@
 // template <class Clock, class Duration>
 //   void sleep_until(const chrono::time_point<Clock, Duration>& abs_time);
 
-#include <thread>
-#include <cstdlib>
 #include <cassert>
+#include <chrono>
+#include <cstdlib>
+#include <thread>
 
 #include "test_macros.h"