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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/110016] Possible miscodegen when inlining
 std::condition_variable::wait predicate causes deadlock
Date: Mon, 29 May 2023 15:15:13 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110016

--- Comment #13 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I suspect if you change the lambda/call to substrate::threadPool_t::waitWor=
k to
be:

                inline std::pair<bool, std::tuple<args_t...>> waitWork()
noexcept
                {
                        std::unique_lock<std::mutex> lock{workMutex};
                        ++waitingThreads;
                        // wait, but protect ourselves from accidental
wake-ups..
                        auto b =3D [this]() noexcept -> bool { bool t =3D f=
inished;
for(volatile int i =3D 0 ; i < 10000;i ++);  return t || !work.empty(); };
                        //if (!b())
                          haveWork.wait(lock, b);
                        --waitingThreads;
                        if (!work.empty())
                                return {true, work.pop()};
                        return {false, {}};
                }



you might hit the issue with more C++ implementations. This should simulates
the issue I was mentioning by adding a slight delay between the load of
finished before the call to wait(lock).=