[Bug libstdc++/57641] std::timed_mutex.try_lock_until() is broken

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57641

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I agree that code assumes the epochs are the same, but what you describe
doesn't make sense since high_resolution_clock and steady_clock have the same
epoch in our implementation.  Are you seeing the first problem described at PR
54562?

Do you have a testcase?