From 4c4a29267cbdd05471322e03bfd5eff8eb68e750 Mon Sep 17 00:00:00 2001 From: Konstantin Belousov Date: Tue, 24 Jan 2023 17:36:24 +0200 Subject: [PATCH] libcxx: add comment explaining why umtx is only used for 64bits Requested by: imp Reviewed by: arichardson, emaste Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D38178 --- contrib/llvm-project/libcxx/src/atomic.cpp | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/contrib/llvm-project/libcxx/src/atomic.cpp b/contrib/llvm-project/libcxx/src/atomic.cpp index 4a2e466bd145..f90d28c2e569 100644 --- a/contrib/llvm-project/libcxx/src/atomic.cpp +++ b/contrib/llvm-project/libcxx/src/atomic.cpp @@ -78,6 +78,11 @@ static void __libcpp_platform_wake_by_address(__cxx_atomic_contention_t const vo } #elif defined(__FreeBSD__) && __SIZEOF_LONG__ == 8 +/* + * Since __cxx_contention_t is int64_t even on 32bit FreeBSD + * platforms, we have to use umtx ops that work on the long type, and + * limit its use to architectures where long and int64_t are synonyms. + */ static void __libcpp_platform_wait_on_address(__cxx_atomic_contention_t const volatile* __ptr, __cxx_contention_t __val)