pre:

    pub fn now() -> Instant {
        let os_now = time::Instant::now();

        // And here we come upon a sad state of affairs. The whole point of
        // `Instant` is that it's monotonically increasing. We've found in the
        // wild, however, that it's not actually monotonically increasing for
        // one reason or another. These appear to be OS and hardware level bugs,
        // and there's not really a whole lot we can do about them. Here's a
        // taste of what we've found:
        //
        // * #48514 - OpenBSD, x86_64
        // * #49281 - linux arm64 and s390x
        // * #51648 - windows, x86
        // * #56560 - windows, x86_64, AWS
        // * #56612 - windows, x86, vm (?)
        // * #56940 - linux, arm64
        // * https://bugzilla.mozilla.org/show_bug.cgi?id=1487778 - a similar
        //   Firefox bug
        //
        // It seems that this just happens a lot in the wild.
        // We're seeing panics across various platforms where consecutive calls
        // to `Instant::now`, such as via the `elapsed` function, are panicking
        // as they're going backwards. Placed here is a last-ditch effort to try
        // to fix things up. We keep a global "latest now" instance which is
        // returned instead of what the OS says if the OS goes backwards.
        //
        // To hopefully mitigate the impact of this, a few platforms are
        // excluded as "these at least haven't gone backwards yet".
        if time::Instant::actually_monotonic() {
            return Instant(os_now);
        }

        Instant(monotonic::monotonize(os_now))
    }