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-rw-r--r--libcxx/CMakeLists.txt20
-rw-r--r--libcxx/include/__config9
-rw-r--r--libcxx/include/__config_site.in1
-rw-r--r--libcxx/include/__threading_support113
-rw-r--r--libcxx/include/thread8
-rw-r--r--libcxx/lib/CMakeLists.txt17
-rw-r--r--libcxx/test/CMakeLists.txt7
-rw-r--r--libcxx/test/libcxx/test/config.py4
-rw-r--r--libcxx/test/libcxx/thread/thread.condition/thread.condition.condvar/native_handle.pass.cpp2
-rw-r--r--libcxx/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/native_handle.pass.cpp2
-rw-r--r--libcxx/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/native_handle.pass.cpp2
-rw-r--r--libcxx/test/libcxx/thread/thread.threads/thread.thread.class/thread.thread.member/native_handle.pass.cpp2
-rw-r--r--libcxx/test/libcxx/thread/thread.threads/thread.thread.class/types.pass.cpp2
-rw-r--r--libcxx/test/lit.site.cfg.in1
-rw-r--r--libcxx/test/support/external_threads.cpp10
15 files changed, 148 insertions, 52 deletions
diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
index da68c594f13..c1391741c6b 100644
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -140,6 +140,9 @@ option(LIBCXX_ENABLE_MONOTONIC_CLOCK
This option may only be set to OFF when LIBCXX_ENABLE_THREADS=OFF." ON)
option(LIBCXX_HAS_MUSL_LIBC "Build libc++ with support for the Musl C library" OFF)
option(LIBCXX_HAS_PTHREAD_API "Ignore auto-detection and force use of pthread API" OFF)
+option(LIBCXX_HAS_EXTERNAL_THREAD_API
+ "Build libc++ with an externalized threading API.
+ This option may only be set to ON when LIBCXX_ENABLE_THREADS=ON." OFF)
# Misc options ----------------------------------------------------------------
# FIXME: Turn -pedantic back ON. It is currently off because it warns
@@ -197,6 +200,11 @@ if(LIBCXX_HAS_PTHREAD_API AND NOT LIBCXX_ENABLE_THREADS)
" when LIBCXX_ENABLE_THREADS is also set to ON.")
endif()
+if(LIBCXX_HAS_EXTERNAL_THREAD_API AND NOT LIBCXX_ENABLE_THREADS)
+ message(FATAL_ERROR "LIBCXX_HAS_EXTERNAL_THREAD_API can only be set to ON"
+ " when LIBCXX_ENABLE_THREADS is also set to ON.")
+endif()
+
# Ensure LLVM_USE_SANITIZER is not specified when LIBCXX_GENERATE_COVERAGE
# is ON.
if (LLVM_USE_SANITIZER AND LIBCXX_GENERATE_COVERAGE)
@@ -371,6 +379,17 @@ if (NOT LIBCXX_ENABLE_RTTI)
add_compile_flags_if_supported(-fno-rtti)
endif()
+# Threading flags =============================================================
+if (LIBCXX_HAS_EXTERNAL_THREAD_API AND LIBCXX_ENABLE_SHARED)
+ # Need to allow unresolved symbols if this is to work with shared library builds
+ if (APPLE)
+ add_link_flags("-undefined dynamic_lookup")
+ else()
+ # Relax this restriction from HandleLLVMOptions
+ string(REPLACE "-Wl,-z,defs" "" CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS}")
+ endif()
+endif()
+
# Assertion flags =============================================================
define_if(LIBCXX_ENABLE_ASSERTIONS -UNDEBUG)
define_if_not(LIBCXX_ENABLE_ASSERTIONS -DNDEBUG)
@@ -432,6 +451,7 @@ config_define_if_not(LIBCXX_ENABLE_MONOTONIC_CLOCK _LIBCPP_HAS_NO_MONOTONIC_CLOC
config_define_if_not(LIBCXX_ENABLE_THREAD_UNSAFE_C_FUNCTIONS _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS)
config_define_if(LIBCXX_HAS_PTHREAD_API _LIBCPP_HAS_THREAD_API_PTHREAD)
+config_define_if(LIBCXX_HAS_EXTERNAL_THREAD_API _LIBCPP_HAS_THREAD_API_EXTERNAL)
config_define_if(LIBCXX_HAS_MUSL_LIBC _LIBCPP_HAS_MUSL_LIBC)
if (LIBCXX_NEEDS_SITE_CONFIG)
diff --git a/libcxx/include/__config b/libcxx/include/__config
index b462191e436..c4e11013ca7 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -831,7 +831,9 @@ extern "C" void __sanitizer_annotate_contiguous_container(
#endif
// Thread API
-#if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
+#if !defined(_LIBCPP_HAS_NO_THREADS) && \
+ !defined(_LIBCPP_HAS_THREAD_API_PTHREAD) && \
+ !defined(_LIBCPP_HAS_THREAD_API_EXTERNAL)
# if defined(__FreeBSD__) || \
defined(__NetBSD__) || \
defined(__linux__) || \
@@ -849,6 +851,11 @@ extern "C" void __sanitizer_annotate_contiguous_container(
_LIBCPP_HAS_NO_THREADS is not defined.
#endif
+#if defined(_LIBCPP_HAS_NO_THREADS) && defined(_LIBCPP_HAS_THREAD_API_EXTERNAL)
+# error _LIBCPP_HAS_EXTERNAL_THREAD_API may not be defined when \
+ _LIBCPP_HAS_NO_THREADS is defined.
+#endif
+
#if defined(_LIBCPP_HAS_NO_MONOTONIC_CLOCK) && !defined(_LIBCPP_HAS_NO_THREADS)
# error _LIBCPP_HAS_NO_MONOTONIC_CLOCK may only be defined when \
_LIBCPP_HAS_NO_THREADS is defined.
diff --git a/libcxx/include/__config_site.in b/libcxx/include/__config_site.in
index 6c2b7bb446d..dce30bc3921 100644
--- a/libcxx/include/__config_site.in
+++ b/libcxx/include/__config_site.in
@@ -20,5 +20,6 @@
#cmakedefine _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
#cmakedefine _LIBCPP_HAS_MUSL_LIBC
#cmakedefine _LIBCPP_HAS_THREAD_API_PTHREAD
+#cmakedefine _LIBCPP_HAS_THREAD_API_EXTERNAL
#endif // _LIBCPP_CONFIG_SITE
diff --git a/libcxx/include/__threading_support b/libcxx/include/__threading_support
index c9a4ea9d094..b36a52ec9cc 100644
--- a/libcxx/include/__threading_support
+++ b/libcxx/include/__threading_support
@@ -19,20 +19,83 @@
#ifndef _LIBCPP_HAS_NO_THREADS
-#if defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
+#if defined(_LIBCPP_HAS_THREAD_API_EXTERNAL) && (!defined(__has_include) || __has_include(<__external_threading>))
+#include <__external_threading>
+#else
#include <pthread.h>
#include <sched.h>
#endif
-_LIBCPP_BEGIN_NAMESPACE_STD
+#if defined(_LIBCPP_HAS_THREAD_API_EXTERNAL)
+#define _LIBCPP_THREAD_ABI_VISIBILITY _LIBCPP_FUNC_VIS
+#else
+#define _LIBCPP_THREAD_ABI_VISIBILITY inline _LIBCPP_INLINE_VISIBILITY
+#endif
-#if defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
+_LIBCPP_BEGIN_NAMESPACE_STD
// Mutex
-#define _LIBCPP_MUTEX_INITIALIZER PTHREAD_MUTEX_INITIALIZER
typedef pthread_mutex_t __libcpp_mutex_t;
+#define _LIBCPP_MUTEX_INITIALIZER PTHREAD_MUTEX_INITIALIZER
+
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_recursive_mutex_init(__libcpp_mutex_t* __m);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_mutex_lock(__libcpp_mutex_t* __m);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_mutex_trylock(__libcpp_mutex_t* __m);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_mutex_unlock(__libcpp_mutex_t* __m);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_mutex_destroy(__libcpp_mutex_t* __m);
+
+// Condition variable
+typedef pthread_cond_t __libcpp_condvar_t;
+#define _LIBCPP_CONDVAR_INITIALIZER PTHREAD_COND_INITIALIZER
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_condvar_signal(__libcpp_condvar_t* __cv);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_condvar_broadcast(__libcpp_condvar_t* __cv);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_condvar_wait(__libcpp_condvar_t* __cv, __libcpp_mutex_t* __m);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_condvar_timedwait(__libcpp_condvar_t* __cv, __libcpp_mutex_t* __m, timespec* __ts);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_condvar_destroy(__libcpp_condvar_t* __cv);
+
+// Thread id
+typedef pthread_t __libcpp_thread_id;
+_LIBCPP_THREAD_ABI_VISIBILITY
+bool __libcpp_thread_id_equal(__libcpp_thread_id t1, __libcpp_thread_id t2);
+_LIBCPP_THREAD_ABI_VISIBILITY
+bool __libcpp_thread_id_less(__libcpp_thread_id t1, __libcpp_thread_id t2);
+
+// Thread
+typedef pthread_t __libcpp_thread_t;
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_thread_create(__libcpp_thread_t* __t, void* (*__func)(void*), void* __arg);
+_LIBCPP_THREAD_ABI_VISIBILITY
+__libcpp_thread_id __libcpp_thread_get_current_id();
+_LIBCPP_THREAD_ABI_VISIBILITY
+__libcpp_thread_id __libcpp_thread_get_id(const __libcpp_thread_t* __t);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_thread_join(__libcpp_thread_t* __t);
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_thread_detach(__libcpp_thread_t* __t);
+_LIBCPP_THREAD_ABI_VISIBILITY
+void __libcpp_thread_yield();
+
+// Thread local storage
+typedef pthread_key_t __libcpp_tls_key;
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_tls_create(__libcpp_tls_key* __key, void (*__at_exit)(void*));
+_LIBCPP_THREAD_ABI_VISIBILITY
+void* __libcpp_tls_get(__libcpp_tls_key __key);
+_LIBCPP_THREAD_ABI_VISIBILITY
+void __libcpp_tls_set(__libcpp_tls_key __key, void* __p);
+
+#if defined(_LIBCPP_HAS_THREAD_API_PTHREAD) || defined(_LIBCPP_BUILDING_EXTERNAL_THREADS)
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_recursive_mutex_init(__libcpp_mutex_t* __m)
{
pthread_mutexattr_t attr;
@@ -59,144 +122,112 @@ int __libcpp_recursive_mutex_init(__libcpp_mutex_t* __m)
return 0;
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_mutex_lock(__libcpp_mutex_t* __m)
{
return pthread_mutex_lock(__m);
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_mutex_trylock(__libcpp_mutex_t* __m)
{
return pthread_mutex_trylock(__m);
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_mutex_unlock(__libcpp_mutex_t* __m)
{
return pthread_mutex_unlock(__m);
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_mutex_destroy(__libcpp_mutex_t* __m)
{
return pthread_mutex_destroy(__m);
}
// Condition variable
-#define _LIBCPP_CONDVAR_INITIALIZER PTHREAD_COND_INITIALIZER
-typedef pthread_cond_t __libcpp_condvar_t;
-
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_condvar_signal(__libcpp_condvar_t* __cv)
{
return pthread_cond_signal(__cv);
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_condvar_broadcast(__libcpp_condvar_t* __cv)
{
return pthread_cond_broadcast(__cv);
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_condvar_wait(__libcpp_condvar_t* __cv, __libcpp_mutex_t* __m)
{
return pthread_cond_wait(__cv, __m);
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_condvar_timedwait(__libcpp_condvar_t* __cv, __libcpp_mutex_t* __m, timespec* __ts)
{
return pthread_cond_timedwait(__cv, __m, __ts);
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_condvar_destroy(__libcpp_condvar_t* __cv)
{
return pthread_cond_destroy(__cv);
}
-// Thread id
-typedef pthread_t __libcpp_thread_id;
-
// Returns non-zero if the thread ids are equal, otherwise 0
-inline _LIBCPP_ALWAYS_INLINE
bool __libcpp_thread_id_equal(__libcpp_thread_id t1, __libcpp_thread_id t2)
{
return pthread_equal(t1, t2) != 0;
}
// Returns non-zero if t1 < t2, otherwise 0
-inline _LIBCPP_ALWAYS_INLINE
bool __libcpp_thread_id_less(__libcpp_thread_id t1, __libcpp_thread_id t2)
{
return t1 < t2;
}
// Thread
-typedef pthread_t __libcpp_thread_t;
-
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_thread_create(__libcpp_thread_t* __t, void* (*__func)(void*), void* __arg)
{
return pthread_create(__t, 0, __func, __arg);
}
-inline _LIBCPP_ALWAYS_INLINE
__libcpp_thread_id __libcpp_thread_get_current_id()
{
return pthread_self();
}
-inline _LIBCPP_ALWAYS_INLINE
__libcpp_thread_id __libcpp_thread_get_id(const __libcpp_thread_t* __t)
{
return *__t;
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_thread_join(__libcpp_thread_t* __t)
{
return pthread_join(*__t, 0);
}
-inline _LIBCPP_ALWAYS_INLINE
int __libcpp_thread_detach(__libcpp_thread_t* __t)
{
return pthread_detach(*__t);
}
-inline _LIBCPP_ALWAYS_INLINE
void __libcpp_thread_yield()
{
sched_yield();
}
// Thread local storage
-typedef pthread_key_t __libcpp_tl_key;
-
-inline _LIBCPP_ALWAYS_INLINE
-int __libcpp_tl_create(__libcpp_tl_key* __key, void (*__at_exit)(void*))
+int __libcpp_tls_create(__libcpp_tls_key* __key, void (*__at_exit)(void*))
{
return pthread_key_create(__key, __at_exit);
}
-inline _LIBCPP_ALWAYS_INLINE
-void* __libcpp_tl_get(__libcpp_tl_key __key)
+void* __libcpp_tls_get(__libcpp_tls_key __key)
{
return pthread_getspecific(__key);
}
-inline _LIBCPP_ALWAYS_INLINE
-void __libcpp_tl_set(__libcpp_tl_key __key, void* __p)
+void __libcpp_tls_set(__libcpp_tls_key __key, void* __p)
{
pthread_setspecific(__key, __p);
}
-#else // !_LIBCPP_HAS_THREAD_API_PTHREAD
- #error "No thread API selected."
-#endif
+#endif // _LIBCPP_HAS_THREAD_API_PTHREAD || _LIBCPP_BUILDING_EXTERNAL_THREADS
_LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/thread b/libcxx/include/thread
index 21cc7610fd0..7fe4c77e1b1 100644
--- a/libcxx/include/thread
+++ b/libcxx/include/thread
@@ -137,7 +137,7 @@ public:
template <class _Tp>
class __thread_specific_ptr
{
- __libcpp_tl_key __key_;
+ __libcpp_tls_key __key_;
// Only __thread_local_data() may construct a __thread_specific_ptr
// and only with _Tp == __thread_struct.
@@ -155,7 +155,7 @@ public:
~__thread_specific_ptr();
_LIBCPP_INLINE_VISIBILITY
- pointer get() const {return static_cast<_Tp*>(__libcpp_tl_get(__key_));}
+ pointer get() const {return static_cast<_Tp*>(__libcpp_tls_get(__key_));}
_LIBCPP_INLINE_VISIBILITY
pointer operator*() const {return *get();}
_LIBCPP_INLINE_VISIBILITY
@@ -173,7 +173,7 @@ __thread_specific_ptr<_Tp>::__at_thread_exit(void* __p)
template <class _Tp>
__thread_specific_ptr<_Tp>::__thread_specific_ptr()
{
- int __ec = __libcpp_tl_create(
+ int __ec = __libcpp_tls_create(
&__key_,
&__thread_specific_ptr::__at_thread_exit);
if (__ec)
@@ -196,7 +196,7 @@ __thread_specific_ptr<_Tp>::set_pointer(pointer __p)
{
_LIBCPP_ASSERT(get() == nullptr,
"Attempting to overwrite thread local data");
- __libcpp_tl_set(__key_, __p);
+ __libcpp_tls_set(__key_, __p);
}
class _LIBCPP_TYPE_VIS thread;
diff --git a/libcxx/lib/CMakeLists.txt b/libcxx/lib/CMakeLists.txt
index dd0f663740d..8ebda513249 100644
--- a/libcxx/lib/CMakeLists.txt
+++ b/libcxx/lib/CMakeLists.txt
@@ -201,6 +201,23 @@ if (LIBCXX_ENABLE_EXPERIMENTAL_LIBRARY)
)
endif()
+if (LIBCXX_HAS_EXTERNAL_THREAD_API)
+ file(GLOB LIBCXX_EXTERNAL_THREADING_SUPPORT_SOURCES ../test/support/external_threads.cpp)
+
+ if (LIBCXX_ENABLE_SHARED)
+ add_library(cxx_external_threads SHARED ${LIBCXX_EXTERNAL_THREADING_SUPPORT_SOURCES})
+ else()
+ add_library(cxx_external_threads STATIC ${LIBCXX_EXTERNAL_THREADING_SUPPORT_SOURCES})
+ endif()
+
+ set_target_properties(cxx_external_threads
+ PROPERTIES
+ LINK_FLAGS "${LIBCXX_LINK_FLAGS}"
+ COMPILE_FLAGS "${LIBCXX_COMPILE_FLAGS}"
+ OUTPUT_NAME "c++external_threads"
+ )
+endif()
+
# Generate a linker script inplace of a libc++.so symlink. Rerun this command
# after cxx builds.
if (LIBCXX_ENABLE_SHARED AND LIBCXX_ENABLE_ABI_LINKER_SCRIPT)
diff --git a/libcxx/test/CMakeLists.txt b/libcxx/test/CMakeLists.txt
index ed6f20d573b..d9be0df8d62 100644
--- a/libcxx/test/CMakeLists.txt
+++ b/libcxx/test/CMakeLists.txt
@@ -22,6 +22,7 @@ pythonize_bool(LIBCXXABI_ENABLE_SHARED)
pythonize_bool(LIBCXXABI_USE_LLVM_UNWINDER)
pythonize_bool(LIBCXX_HAS_ATOMIC_LIB)
pythonize_bool(LIBCXX_HAVE_CXX_ATOMICS_WITH_LIB)
+pythonize_bool(LIBCXX_HAS_EXTERNAL_THREAD_API)
# The tests shouldn't link to any ABI library when it has been linked into
# libc++ statically or via a linker script.
@@ -52,10 +53,14 @@ if (LIBCXX_ENABLE_EXPERIMENTAL_LIBRARY)
set(experimental_dep cxx_experimental)
endif()
+if (LIBCXX_HAS_EXTERNAL_THREAD_API)
+ set(external_threads_dep cxx_external_threads)
+endif()
+
add_lit_testsuite(check-cxx
"Running libcxx tests"
${CMAKE_CURRENT_BINARY_DIR}
- DEPENDS cxx ${experimental_dep})
+ DEPENDS cxx ${experimental_dep} ${external_threads_dep})
add_custom_target(check-libcxx DEPENDS check-cxx)
diff --git a/libcxx/test/libcxx/test/config.py b/libcxx/test/libcxx/test/config.py
index 579089a9501..70f2094aac9 100644
--- a/libcxx/test/libcxx/test/config.py
+++ b/libcxx/test/libcxx/test/config.py
@@ -510,6 +510,10 @@ class Configuration(object):
self.cxx.link_flags += [abs_path]
else:
self.cxx.link_flags += ['-lc++']
+ # This needs to come after -lc++ as we want its unresolved thread-api symbols
+ # to be picked up from this one.
+ if self.get_lit_bool('libcxx_external_thread_api', default=False):
+ self.cxx.link_flags += ['-lc++external_threads']
def configure_link_flags_abi_library(self):
cxx_abi = self.get_lit_conf('cxx_abi', 'libcxxabi')
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
index bf28e01a0e8..6ebba1467db 100644
--- 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
@@ -7,7 +7,7 @@
//
//===----------------------------------------------------------------------===//
//
-// UNSUPPORTED: libcpp-has-no-threads
+// UNSUPPORTED: libcpp-has-no-threads, libcpp-has-thread-api-external
// <condition_variable>
diff --git a/libcxx/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/native_handle.pass.cpp b/libcxx/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/native_handle.pass.cpp
index 12c80f02c34..c6ed66ce41d 100644
--- a/libcxx/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/native_handle.pass.cpp
+++ b/libcxx/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/native_handle.pass.cpp
@@ -7,7 +7,7 @@
//
//===----------------------------------------------------------------------===//
//
-// UNSUPPORTED: libcpp-has-no-threads
+// UNSUPPORTED: libcpp-has-no-threads, libcpp-has-thread-api-external
// <mutex>
diff --git a/libcxx/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/native_handle.pass.cpp b/libcxx/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/native_handle.pass.cpp
index 10626bc4072..2031e4d7d4b 100644
--- a/libcxx/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/native_handle.pass.cpp
+++ b/libcxx/test/libcxx/thread/thread.mutex/thread.mutex.requirements/thread.mutex.requirements.mutex/thread.mutex.recursive/native_handle.pass.cpp
@@ -7,7 +7,7 @@
//
//===----------------------------------------------------------------------===//
//
-// UNSUPPORTED: libcpp-has-no-threads
+// UNSUPPORTED: libcpp-has-no-threads, libcpp-has-thread-api-external
// <mutex>
diff --git a/libcxx/test/libcxx/thread/thread.threads/thread.thread.class/thread.thread.member/native_handle.pass.cpp b/libcxx/test/libcxx/thread/thread.threads/thread.thread.class/thread.thread.member/native_handle.pass.cpp
index c8807a965c4..1b1cbf89a09 100644
--- a/libcxx/test/libcxx/thread/thread.threads/thread.thread.class/thread.thread.member/native_handle.pass.cpp
+++ b/libcxx/test/libcxx/thread/thread.threads/thread.thread.class/thread.thread.member/native_handle.pass.cpp
@@ -7,7 +7,7 @@
//
//===----------------------------------------------------------------------===//
//
-// UNSUPPORTED: libcpp-has-no-threads
+// UNSUPPORTED: libcpp-has-no-threads, libcpp-has-thread-api-external
// <thread>
diff --git a/libcxx/test/libcxx/thread/thread.threads/thread.thread.class/types.pass.cpp b/libcxx/test/libcxx/thread/thread.threads/thread.thread.class/types.pass.cpp
index a5bf77031cc..e864af7f05b 100644
--- a/libcxx/test/libcxx/thread/thread.threads/thread.thread.class/types.pass.cpp
+++ b/libcxx/test/libcxx/thread/thread.threads/thread.thread.class/types.pass.cpp
@@ -7,7 +7,7 @@
//
//===----------------------------------------------------------------------===//
//
-// UNSUPPORTED: libcpp-has-no-threads
+// UNSUPPORTED: libcpp-has-no-threads, libcpp-has-thread-api-external
// <thread>
diff --git a/libcxx/test/lit.site.cfg.in b/libcxx/test/lit.site.cfg.in
index a1ae90cb479..943c840fa22 100644
--- a/libcxx/test/lit.site.cfg.in
+++ b/libcxx/test/lit.site.cfg.in
@@ -26,6 +26,7 @@ config.has_libatomic = "@LIBCXX_HAS_ATOMIC_LIB@"
config.use_libatomic = "@LIBCXX_HAVE_CXX_ATOMICS_WITH_LIB@"
config.libcxxabi_shared = "@LIBCXXABI_ENABLE_SHARED@"
+config.libcxx_external_thread_api = "@LIBCXX_HAS_EXTERNAL_THREAD_API@"
# Let the main config do the real work.
lit_config.load_config(config, "@LIBCXX_SOURCE_DIR@/test/lit.cfg")
diff --git a/libcxx/test/support/external_threads.cpp b/libcxx/test/support/external_threads.cpp
new file mode 100644
index 00000000000..381ec651eef
--- /dev/null
+++ b/libcxx/test/support/external_threads.cpp
@@ -0,0 +1,10 @@
+//===----------------------------------------------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#define _LIBCPP_BUILDING_EXTERNAL_THREADS
+#include <__threading_support>
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