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

On 10/1/19 8:09 AM, Jens Axboe wrote:

quoted

On 9/30/19 2:20 PM, Arnd Bergmann wrote:

quoted

All system calls use struct __kernel_timespec instead of the old struct
timespec, but this one was just added with the old-style ABI. Change it
now to enforce the use of __kernel_timespec, avoiding ABI confusion and
the need for compat handlers on 32-bit architectures.

Any user space caller will have to use __kernel_timespec now, but this
is unambiguous and works for any C library regardless of the time_t
definition. A nicer way to specify the timeout would have been a less
ambiguous 64-bit nanosecond value, but I suppose it's too late now to
change that as this would impact both 32-bit and 64-bit users.

Thanks for catching that, Arnd. Applied.

On second thought - since there appears to be no good 64-bit timespec
available to userspace, the alternative here is including on in liburing.

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.

That seems kinda crappy in terms of API, so why not just use a 64-bit nsec
value as you suggest? There's on released kernel with this feature yet, so
there's nothing stopping us from just changing the API to be based on
a single 64-bit nanosecond timeout.

Certainly fine with me.

+       timeout = READ_ONCE(sqe->addr);
        hrtimer_init(&req->timeout.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
        req->timeout.timer.function = io_timeout_fn;
-       hrtimer_start(&req->timeout.timer, timespec_to_ktime(ts),
+       hrtimer_start(&req->timeout.timer, ns_to_ktime(timeout),

It seems a little odd to use the 'addr' field as something that's not
an address,
and I'm not sure I understand the logic behind when you use a READ_ONCE()
as opposed to simply accessing the sqe the way it is done a few lines
earlier.

The time handling definitely looks good to me.

       Arnd