fcntl(F_DUPFD_CLOEXEC) reached redox_rt/kernel with the POSIX/C value 1030
instead of the Redox syscall value (syscall::F_DUPFD_CLOEXEC=5). redox_rt did
not recognize it as a dup, forwarded the raw command to the kernel, and the
kernel's fcntl fell through to its EINVAL catch-all. That made
OwnedFd::try_clone() return EINVAL, which broke tokio Runtime::build() (its I/O
reactor try_clones the epoll fd) for every tokio user on Redox: all the zbus
system daemons (sessiond/polkit/udisks/upower) and the login shell. F_DUPFD and
plain dup worked because they share the same value in both namespaces;
F_DUPFD_CLOEXEC was the sole untranslated command.
Also drop the ineffective epoll_ctl EINVAL/EBADF retry loop: it was based on a
disproven 'transient scheme churn' theory; epoll registrations always succeed
immediately. The real dup failure is fixed above.
Red Bear OS
733da06876