Re: [PATCH] io_uring: use __kernel_timespec in timeout ABI

[Arnd Bergmann]

On Tue, Oct 1, 2019 at 5:52 PM Jens Axboe <axboe@xxxxxxxxx> wrote:
> On 10/1/19 9:49 AM, Arnd Bergmann wrote:
> > On Tue, Oct 1, 2019 at 5:38 PM Jens Axboe <axboe@xxxxxxxxx> wrote:

> > What's wrong with using __kernel_timespec? Just the name?
> > I suppose liburing could add a macro to give it a different name
> > for its users.
>
> Just that it seems I need to make it available through liburing on
> systems that don't have it yet. Not a big deal, though.

Ah, right. I t would not cover the case of building against kernel
headers earlier than linux-5.1 but running on a 5.4+ kernel.

I assumed that that you would require new kernel headers anyway,
but if you have a copy of the io_uring header, that is not necessary.

> One thing that struck me about this approach - we then lose the ability to
> differentiate between "don't want a timed timeout" with ts == NULL, vs
> tv_sec and tv_nsec both being 0.

You could always define a special constant such as
'#define IO_URING_TIMEOUT_NEVER -1ull' if you want to
support for 'never wait if it's not already done' and 'wait indefinitely'.

> I think I'll stuck with that you had and just use __kernel_timespec in
> liburing.

Ok.

       Arnd