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author | Kuba Brecka <kuba.brecka@gmail.com> | 2016-09-04 09:55:12 +0000 |
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committer | Kuba Brecka <kuba.brecka@gmail.com> | 2016-09-04 09:55:12 +0000 |
commit | 4dbd4fcf8626453949625bf36976e668094cfbb1 (patch) | |
tree | bb56168016d3cf4cd4a0f4cee12287b95d2aecb6 /include/memory | |
parent | 226cd0674ec0ef4db9c126373e30078f33526d7e (diff) |
[libcxx] Fix a data race in call_once
call_once is using relaxed atomic load to perform double-checked locking, which contains a data race. The fast-path load has to be an acquire atomic load.
Differential Revision: https://reviews.llvm.org/D24028
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@280621 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'include/memory')
-rw-r--r-- | include/memory | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/include/memory b/include/memory index 31f58b7c0..8cb094e6b 100644 --- a/include/memory +++ b/include/memory @@ -663,6 +663,18 @@ _ValueType __libcpp_relaxed_load(_ValueType const* __value) { #endif } +template <class _ValueType> +inline _LIBCPP_ALWAYS_INLINE +_ValueType __libcpp_acquire_load(_ValueType const* __value) { +#if !defined(_LIBCPP_HAS_NO_THREADS) && \ + defined(__ATOMIC_ACQUIRE) && \ + (__has_builtin(__atomic_load_n) || _GNUC_VER >= 407) + return __atomic_load_n(__value, __ATOMIC_ACQUIRE); +#else + return *__value; +#endif +} + // addressof moved to <__functional_base> template <class _Tp> class allocator; |