On 10/1/19 9:57 AM, Arnd Bergmann wrote: > 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. Since I rely mostly on folks using liburing, we include the header as well. So I'm just going to use __kernel_timespec in liburing, and have a check to define it if we don't have it. >> 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'. That thought did occur to me, but that seems pretty ugly... The ts == NULL vs ts != NULL and timeout set is a more well understood pattern. -- Jens Axboe
