Re: [PATCH] rust: time: New module for timekeeping functions

[Josh Stone]

On 2/21/23 4:32 AM, Thomas Gleixner wrote:
> Now the problem is that 'Instant' in it's specification is bound to
> CLOCK_MONOTONIC and there is no way to express CLOCK_BOOTTIME, but
> that's a shortcoming of the spec which ignores CLOCK_BOOTTIME
> completely. IOW, that's also a problem for user space.

That's not exactly *specified* -- it's meant to be opaque time. It is
documented that this currently uses clock_gettime monotonic on unix
targets, but "Disclaimer: These system calls might change over time."
CLOCK_MONOTONIC isn't even consistent across unix targets whether that
counts suspended time. It's been debated if we should switch to
CLOCK_BOOTTIME on Linux, but for now we're sticking to monotonic:

https://github.com/rust-lang/rust/pull/88714

But as others mentioned, this is in the std crate which isn't used by
the kernel. You could absolutely define your own with more specificity,
like kernel::time::BootTime, and copy an API similar to Instant's.