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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 15:37:53 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110016

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #15 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Rachel Mant from comment #14)=20
> To properly understand this problem space, why do you think locking the
> mutex before setting `finished` is sufficient to fix this? It feels to us
> like it shouldn't, and should only mask the bug, making it less likely to
> trigger?

So currently wait (and the check of finished) is under the mutex, workMutex=
. If
you want to modify finish, it needs to be under the same mutex.


Note https://en.cppreference.com/w/cpp/thread/condition_variable mentiones =
the
exact fix too.

And even has the following: "Even if the shared variable is atomic, it must=
 be
modified while owning the mutex to correctly publish the modification to the
waiting thread."

(this part was added back in 2015:
https://en.cppreference.com/mwiki/index.php?title=3Dcpp/thread/condition_va=
riable&diff=3D81211&oldid=3D80448
)

So I think I can now close this as invalid.=