tavianator updated this revision to Diff 62691.
tavianator added a comment.
Added a test case for destructor ordering. Got rid of
pthread_{get,set}specific in a loop.
http://reviews.llvm.org/D21803
Files:
cmake/config-ix.cmake
src/CMakeLists.txt
src/cxa_thread_atexit.cpp
test/CMakeLists.txt
test/cxa_thread_atexit_test.pass.cpp
test/libcxxabi/test/config.py
test/lit.site.cfg.in
test/thread_local_destruction_order.pass.cpp
Index: test/thread_local_destruction_order.pass.cpp
===================================================================
--- test/thread_local_destruction_order.pass.cpp
+++ test/thread_local_destruction_order.pass.cpp
@@ -0,0 +1,59 @@
+//===--------------------- cxa_thread_atexit_test.cpp ---------------------===//
+//
+// 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.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+#include <cassert>
+#include <thread>
+
+int seq = 0;
+
+class OrderChecker
+{
+public:
+ explicit OrderChecker(int n) : n_{n} { }
+
+ ~OrderChecker() {
+ assert(seq++ == n_);
+ }
+
+private:
+ int n_;
+};
+
+class CreatesThreadLocalInDestructor
+{
+public:
+ CreatesThreadLocalInDestructor(int n) : n_{n} { }
+
+ ~CreatesThreadLocalInDestructor() {
+ thread_local OrderChecker checker{n_};
+ }
+
+private:
+ int n_;
+};
+
+OrderChecker global{5};
+
+void thread_fn() {
+ static OrderChecker fn_static{3};
+ thread_local OrderChecker fn_thread_local{0};
+}
+
+int main() {
+ static OrderChecker fn_static{4};
+
+ std::thread{thread_fn}.join();
+
+ thread_local OrderChecker fn_thread_local{2};
+ thread_local CreatesThreadLocalInDestructor creates_tl{1};
+
+ return 0;
+}
Index: test/lit.site.cfg.in
===================================================================
--- test/lit.site.cfg.in
+++ test/lit.site.cfg.in
@@ -13,7 +13,6 @@
config.enable_32bit = "@LIBCXXABI_BUILD_32_BITS@"
config.target_info = "@LIBCXXABI_TARGET_INFO@"
config.executor = "@LIBCXXABI_EXECUTOR@"
-config.thread_atexit = "@LIBCXXABI_HAS_CXA_THREAD_ATEXIT_IMPL@"
config.libcxxabi_shared = "@LIBCXXABI_ENABLE_SHARED@"
config.enable_shared = "@LIBCXX_ENABLE_SHARED@"
config.enable_exceptions = "@LIBCXXABI_ENABLE_EXCEPTIONS@"
Index: test/libcxxabi/test/config.py
===================================================================
--- test/libcxxabi/test/config.py
+++ test/libcxxabi/test/config.py
@@ -37,8 +37,6 @@
super(Configuration, self).configure_features()
if not self.get_lit_bool('enable_exceptions', True):
self.config.available_features.add('libcxxabi-no-exceptions')
- if self.get_lit_bool('thread_atexit', True):
- self.config.available_features.add('thread_atexit')
def configure_compile_flags(self):
self.cxx.compile_flags += ['-DLIBCXXABI_NO_TIMER']
Index: test/cxa_thread_atexit_test.pass.cpp
===================================================================
--- test/cxa_thread_atexit_test.pass.cpp
+++ test/cxa_thread_atexit_test.pass.cpp
@@ -8,7 +8,6 @@
//===----------------------------------------------------------------------===//
// REQUIRES: linux
-// REQUIRES: thread_atexit
#include <assert.h>
#include <cxxabi.h>
Index: test/CMakeLists.txt
===================================================================
--- test/CMakeLists.txt
+++ test/CMakeLists.txt
@@ -16,7 +16,6 @@
pythonize_bool(LIBCXXABI_ENABLE_THREADS)
pythonize_bool(LIBCXXABI_ENABLE_EXCEPTIONS)
pythonize_bool(LIBCXXABI_USE_LLVM_UNWINDER)
-pythonize_bool(LIBCXXABI_HAS_CXA_THREAD_ATEXIT_IMPL)
set(LIBCXXABI_TARGET_INFO "libcxx.test.target_info.LocalTI" CACHE STRING
"TargetInfo to use when setting up test environment.")
set(LIBCXXABI_EXECUTOR "None" CACHE STRING
Index: src/cxa_thread_atexit.cpp
===================================================================
--- src/cxa_thread_atexit.cpp
+++ src/cxa_thread_atexit.cpp
@@ -7,20 +7,126 @@
//
//===----------------------------------------------------------------------===//
+#include "abort_message.h"
#include "cxxabi.h"
+#include <cstdlib>
+#include <pthread.h>
namespace __cxxabiv1 {
+namespace {
+ // This implementation is used if the C library does not provide
+ // __cxa_thread_atexit_impl() for us. It has a number of limitations that are
+ // difficult to impossible to address without ..._impl():
+ //
+ // - dso_symbol is ignored. This means that a shared library may be unloaded
+ // (via dlclose()) before its thread_local destructors have run.
+ //
+ // - thread_local destructors for the main thread are run by the destructor of
+ // a static object. This is later than expected; they should run before the
+ // destructors of any objects with static storage duration.
+ //
+ // - thread_local destructors on other threads run on the first iteration
+ // through the pthread_key destructors. std::notify_all_at_thread_exit()
+ // and similar functions must be careful to wait until the second iteration
+ // to provide their indended ordering guarantees.
+
+ using Dtor = void(*)(void*);
+
+ struct DtorList {
+ Dtor dtor;
+ void* obj;
+ DtorList* next;
+ };
+
+ pthread_key_t dtors;
+
+ void run_dtors(void* ptr) {
+ // pthread_key destructors run after the key is set to NULL, but we need to
+ // restore it here to get the right ordering if __cxa_thread_atexit() is
+ // called during the loop.
+ if (pthread_setspecific(dtors, ptr) != 0) {
+ abort_message("pthread_setspecific() failed during thread_local destruction");
+ }
+
+ auto list = static_cast<DtorList**>(ptr);
+
+ while (auto head = *list) {
+ *list = head->next;
+ head->dtor(head->obj);
+ std::free(head);
+ }
+
+ std::free(list);
+
+ // Set the pthread_key to NULL (or else the destructor would run again)
+ if (pthread_setspecific(dtors, NULL) != 0) {
+ abort_message("pthread_setspecific() failed during thread_local destruction");
+ }
+ }
+
+ struct DtorsManager
+ {
+ DtorsManager() {
+ // There is intentionally no matching pthread_key_delete call, as
+ // __cxa_thread_atexit() may be called arbitrarily late (for example, from
+ // global destructors or atexit() handlers).
+ if (pthread_key_create(&dtors, run_dtors) != 0) {
+ abort_message("pthread_key_create() failed in __cxa_thread_atexit()");
+ }
+ }
+
+ ~DtorsManager() {
+ // pthread_key destructors do not run on threads that call exit()
+ // (including when the main thread returns from main()), so we explicitly
+ // call the destructor here. This runs at exit time (potentially earlier
+ // if libc++abi is dlclose()'d).
+ auto ptr = pthread_getspecific(dtors);
+ if (ptr) {
+ run_dtors(ptr);
+ }
+ }
+ };
+} // namespace
+
extern "C" {
-#ifdef HAVE___CXA_THREAD_ATEXIT_IMPL
+_LIBCXXABI_FUNC_VIS int __cxa_thread_atexit(Dtor dtor, void* obj,
+ void* dso_symbol) throw() {
+ // A weak symbol is used to detect this function's presence in the C library
+ extern int __cxa_thread_atexit_impl(Dtor, void*, void*)
+ __attribute__((__weak__));
+
+ if (__cxa_thread_atexit_impl) {
+ return __cxa_thread_atexit_impl(dtor, obj, dso_symbol);
+ } else {
+ // Initialize the dtors pthread_key (uses __cxa_guard_*() for one-time
+ // initialization and __cxa_atexit() for destruction)
+ static DtorsManager manager;
+
+ auto list = static_cast<DtorList**>(pthread_getspecific(dtors));
+ if (!list) {
+ list = static_cast<DtorList**>(std::malloc(sizeof(DtorList*)));
+ if (!list) {
+ return -1;
+ }
+ if (pthread_setspecific(dtors, list) != 0) {
+ return -1;
+ }
+ }
+
+ auto head = static_cast<DtorList*>(std::malloc(sizeof(DtorList)));
+ if (!head) {
+ return -1;
+ }
+
+ head->dtor = dtor;
+ head->obj = obj;
+ head->next = *list;
+ *list = head;
-_LIBCXXABI_FUNC_VIS int __cxa_thread_atexit(void (*dtor)(void *), void *obj,
- void *dso_symbol) throw() {
- extern int __cxa_thread_atexit_impl(void (*)(void *), void *, void *);
- return __cxa_thread_atexit_impl(dtor, obj, dso_symbol);
+ return 0;
+ }
}
-#endif // HAVE__CXA_THREAD_ATEXIT_IMPL
-
} // extern "C"
} // namespace __cxxabiv1
Index: src/CMakeLists.txt
===================================================================
--- src/CMakeLists.txt
+++ src/CMakeLists.txt
@@ -41,10 +41,6 @@
include_directories("${LIBCXXABI_LIBCXX_INCLUDES}")
-if (LIBCXXABI_HAS_CXA_THREAD_ATEXIT_IMPL)
- add_definitions(-DHAVE___CXA_THREAD_ATEXIT_IMPL)
-endif()
-
# Generate library list
set(libraries ${LIBCXXABI_CXX_ABI_LIBRARIES})
Index: cmake/config-ix.cmake
===================================================================
--- cmake/config-ix.cmake
+++ cmake/config-ix.cmake
@@ -43,5 +43,3 @@
check_library_exists(dl dladdr "" LIBCXXABI_HAS_DL_LIB)
check_library_exists(pthread pthread_once "" LIBCXXABI_HAS_PTHREAD_LIB)
check_library_exists(gcc_s __gcc_personality_v0 "" LIBCXXABI_HAS_GCC_S_LIB)
-check_library_exists(c __cxa_thread_atexit_impl ""
- LIBCXXABI_HAS_CXA_THREAD_ATEXIT_IMPL)
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