On 10/1/19 9:49 AM, Arnd Bergmann wrote:
On Tue, Oct 1, 2019 at 5:38 PM Jens Axboe axboe@kernel.dk wrote:
On 10/1/19 8:09 AM, Jens Axboe wrote:
On 9/30/19 2:20 PM, Arnd Bergmann wrote:
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.
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.
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.
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.
I think I'll stuck with that you had and just use __kernel_timespec in liburing.