From d0ad5eb1bf8ba3703489856c05ec108d99b539d8 Mon Sep 17 00:00:00 2001 From: Louis Dionne Date: Thu, 25 Jul 2019 20:29:20 +0000 Subject: [PATCH] [NFC][libcxx] Add comments about making mutex/condition_variable trivial on Apple platforms Leaving some comments behind so that we avoid re-having that discussion in the future. git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@367048 91177308-0d34-0410-b5e6-96231b3b80d8 --- include/__config | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/include/__config b/include/__config index 61ca54479..682b9909b 100644 --- a/include/__config +++ b/include/__config @@ -1097,17 +1097,27 @@ _LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container( _LIBCPP_HAS_NO_THREADS is defined. #endif -// The Apple, glibc, and Bionic implementation of pthreads implements +// The glibc and Bionic implementation of pthreads implements // pthread_mutex_destroy as nop for regular mutexes. Additionally, Win32 // mutexes have no destroy mechanism. -// TODO(EricWF): Enable this optimization on Apple and Bionic platforms after -// speaking to their respective stakeholders. +// +// This optimization can't be performed on Apple platforms, where +// pthread_mutex_destroy can allow the kernel to release resources. +// See https://llvm.org/D64298 for details. +// +// TODO(EricWF): Enable this optimization on Bionic after speaking to their +// respective stakeholders. #if (defined(_LIBCPP_HAS_THREAD_API_PTHREAD) && defined(__GLIBC__)) \ || defined(_LIBCPP_HAS_THREAD_API_WIN32) # define _LIBCPP_HAS_TRIVIAL_MUTEX_DESTRUCTION #endif // Destroying a condvar is a nop on Windows. +// +// This optimization can't be performed on Apple platforms, where +// pthread_cond_destroy can allow the kernel to release resources. +// See https://llvm.org/D64298 for details. +// // TODO(EricWF): This is potentially true for some pthread implementations // as well. #if defined(_LIBCPP_HAS_THREAD_API_WIN32)