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| author | Jonathan Wakely <jwakely@redhat.com> | 2022-05-17 15:17:21 (GMT) |
|---|---|---|
| committer | Jonathan Wakely <jwakely@redhat.com> | 2022-05-17 19:53:40 (GMT) |
| commit | ddb1427defe95341ac2eb672e7bea7303f8c7db9 (patch) | |
| tree | 90c89ddc1745b295c25b34ea1d879f4fb6f556c2 | |
| parent | 5c2d703e6d6d47f41635ca4df06c555010462081 (diff) | |
| download | gcc-ddb1427defe95341ac2eb672e7bea7303f8c7db9.zip gcc-ddb1427defe95341ac2eb672e7bea7303f8c7db9.tar.gz gcc-ddb1427defe95341ac2eb672e7bea7303f8c7db9.tar.bz2 | |
libstdc++: Relax memory ordering for default memory resource object
Currently pmr::set_default_resource and pmr::get_default_resource both
use sequentially consistent memory ordering. This is overkill. The
standard only requires that a call to set_default_resource synchronizes
with subsequent calls to set_default_resource and get_default_resource.
Using acquire-release for the setter and acquire for the getter is
sufficient to meet the requirement.
Reviewed-by: Thomas Rodgers <trodgers@redhat.com>
libstdc++-v3/ChangeLog:
* src/c++17/memory_resource.cc (set_default_resource): Use
memory_order_acq_rel.
(get_default_resource): Use memory_order_acquire.
| -rw-r--r-- | libstdc++-v3/src/c++17/memory_resource.cc | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/libstdc++-v3/src/c++17/memory_resource.cc b/libstdc++-v3/src/c++17/memory_resource.cc index bb6334c..8bc55a6 100644 --- a/libstdc++-v3/src/c++17/memory_resource.cc +++ b/libstdc++-v3/src/c++17/memory_resource.cc @@ -112,13 +112,13 @@ namespace pmr mutex mx; memory_resource* val; - memory_resource* load() + memory_resource* load(std::memory_order) { lock_guard<mutex> lock(mx); return val; } - memory_resource* exchange(memory_resource* r) + memory_resource* exchange(memory_resource* r, std::memory_order) { lock_guard<mutex> lock(mx); return std::__exchange(val, r); @@ -134,12 +134,12 @@ namespace pmr memory_resource* val; - memory_resource* load() const + memory_resource* load(std::memory_order) const { return val; } - memory_resource* exchange(memory_resource* r) + memory_resource* exchange(memory_resource* r, std::memory_order) { return std::__exchange(val, r); } @@ -166,12 +166,12 @@ namespace pmr { if (r == nullptr) r = new_delete_resource(); - return default_res.obj.exchange(r); + return default_res.obj.exchange(r, std::memory_order_acq_rel); } memory_resource* get_default_resource() noexcept - { return default_res.obj.load(); } + { return default_res.obj.load(std::memory_order_acquire); } // Member functions for std::pmr::monotonic_buffer_resource |