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* [gcc r12-6708] libstdc++: Fix std::atomic<std::shared_ptr<T>> for AIX [PR104101]
@ 2022-01-19 1:03 Jonathan Wakely
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From: Jonathan Wakely @ 2022-01-19 1:03 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:c3861f79859d96777f86a24261fe639538fd2e1c
commit r12-6708-gc3861f79859d96777f86a24261fe639538fd2e1c
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Tue Jan 18 21:15:05 2022 +0000
libstdc++: Fix std::atomic<std::shared_ptr<T>> for AIX [PR104101]
This fixes an on AIX.
The lock function currently just spins, which should be changed to use
back-off, and maybe then _M_val.wait(__current) when supported.
libstdc++-v3/ChangeLog:
PR libstdc++/104101
* include/bits/shared_ptr_atomic.h (_Sp_atomic::_Atomic_count::lock):
Only use __thread_relax if __cpp_lib_atomic_wait is defined.
Diff:
---
libstdc++-v3/include/bits/shared_ptr_atomic.h | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/libstdc++-v3/include/bits/shared_ptr_atomic.h b/libstdc++-v3/include/bits/shared_ptr_atomic.h
index 50aa46370ca..35f781dc9a0 100644
--- a/libstdc++-v3/include/bits/shared_ptr_atomic.h
+++ b/libstdc++-v3/include/bits/shared_ptr_atomic.h
@@ -392,7 +392,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
auto __current = _M_val.load(memory_order_relaxed);
while (__current & _S_lock_bit)
{
+#if __cpp_lib_atomic_wait
__detail::__thread_relax();
+#endif
__current = _M_val.load(memory_order_relaxed);
}
@@ -401,7 +403,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__o,
memory_order_relaxed))
{
+#if __cpp_lib_atomic_wait
__detail::__thread_relax();
+#endif
__current = __current & ~_S_lock_bit;
}
return reinterpret_cast<pointer>(__current);
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