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From: "rth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug libstdc++/65033] C++11 atomics: is_lock_free result does not always match the real lock-free property Date: Thu, 12 Feb 2015 19:30:00 -0000 [thread overview] Message-ID: <bug-65033-4-ZiXAjRMI5J@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-65033-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65033 --- Comment #6 from Richard Henderson <rth at gcc dot gnu.org> --- (In reply to Bin Fan from comment #5) > So after the fix, atomic_is_lock_free will always return 0 for > size=3,align=1 atomic struct objects? Yes. > I understand currently libatomic tries to make an atomic object lock-free if > its memory location fit in a certain sized window. So for atomic operations > such as atomic_store where the actual address is passed in, the operation > can be still either lock-free or locked, right? Yes. > I'm wondering if it's standard conforming since the lock-free property > is still per-object, or it can be seen as an optimization, i.e. > atomic_is_lock_free query for the > object returns 0, but atomic operations on the object could be lock-free. My understanding is that it's valid to optimize the operation to lock-free, but since there may exist objects for which we will have to use the lock, the atomic_is_lock_free query must return false.
next prev parent reply other threads:[~2015-02-12 19:30 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-02-12 6:02 [Bug libstdc++/65033] New: " bin.x.fan at oracle dot com 2015-02-12 7:12 ` [Bug libstdc++/65033] " pinskia at gcc dot gnu.org 2015-02-12 8:49 ` redi at gcc dot gnu.org 2015-02-12 17:16 ` jason at gcc dot gnu.org 2015-02-12 17:47 ` rth at gcc dot gnu.org 2015-02-12 18:43 ` bin.x.fan at oracle dot com 2015-02-12 19:30 ` rth at gcc dot gnu.org [this message] 2015-03-26 18:47 ` rth at gcc dot gnu.org 2015-03-26 18:51 ` rth at gcc dot gnu.org 2015-07-16 15:51 ` bin.x.fan at oracle dot com
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