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From: "fw at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/101761] Random hang with
 29_atomics/atomic_ref/wait_notify.cc
Date: Wed, 15 Sep 2021 08:56:00 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101761

Florian Weimer <fw at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fw at gcc dot gnu.org

--- Comment #4 from Florian Weimer <fw at gcc dot gnu.org> ---
I think it's a test bug:

      std::atomic_ref<S> a{ aa };

      std::thread t([&]
        {
          a.store(bb);
          a.notify_one();
        });
      a.wait(aa);

Due to the use of std::atomic_ref, store() overwrites aa with the value of =
bb.
If the notify_one() call completes before the wait() call, wait() blocks
because aa =3D=3D bb (due to the previous store()), and the wakeup never ha=
ppens
because wakes are not queued.=