internal/poll, runtime: handle netpollopen error in poll_runtime_pollOpen
When netpollopen in poll_runtime_pollOpen returns an error, the work in
runtime_pollUnblock and runtime_pollClose can be avoided since the
underlying system call to set up the poller failed.
E.g. on linux, this avoids calling netpollclose and thus epoll_ctl(fd,
EPOLL_CTL_DEL, ...) in case the file does not support epoll, i.e.
epoll_ctl(fd, EPOLL_CTL_ADD, ...) in netpollopen failed.
Fixes #44552
Change-Id: I564d90340fd1ab3a6490526353616a447ae0cfb8
Reviewed-on: https://go-review.googlesource.com/c/go/+/297392
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>