[Bug libstdc++/60966] std::call_once sometime hangs

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60966

--- Comment #15 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Hideaki Kimura from comment #14)
> I'm not sure if this helps, but could you try the following code snippet?

Very helpful, thanks