On 10/1/19 9:57 AM, Arnd Bergmann wrote:

On Tue, Oct 1, 2019 at 5:52 PM Jens Axboe [off-list ref] wrote:

quoted

On 10/1/19 9:49 AM, Arnd Bergmann wrote:

quoted

On Tue, Oct 1, 2019 at 5:38 PM Jens Axboe [off-list ref] wrote:

quoted

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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.

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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