Re: [PATCH v3 RESEND] io_uring: add timeout support for io_uring_enter()

Jens Axboe
2020-11-04T19:34:04Z

On 11/4/20 12:27 PM, Pavel Begunkov wrote:
> On 04/11/2020 18:32, Jens Axboe wrote:
>> On 11/4/20 10:50 AM, Jens Axboe wrote:
>>> +struct io_uring_getevents_arg {
>>> + sigset_t *sigmask;
>>> + struct __kernel_timespec *ts;
>>> +};
>>> +
>>
>> I missed that this is still not right, I did bring it up in your last
>> posting though - you can't have pointers as a user API, since the size
>> of the pointer will vary depending on whether this is a 32-bit or 64-bit
>> arch (or 32-bit app running on 64-bit kernel).
>
> Maybe it would be better
>
> 1) to kill this extra indirection?
>
> struct io_uring_getevents_arg {
> - sigset_t *sigmask;
> - struct __kernel_timespec *ts;
> + sigset_t sigmask;
> + struct __kernel_timespec ts;
> };
>
> then,
>
> sigset_t *sig = (...)arg;
> __kernel_timespec* ts = (...)(arg + offset);

But then it's kind of hard to know which, if any, of them are set... I
did think about this, and any solution seemed worse than just having the
extra indirection.

Yeah, not doing the extra indirection would save a copy, but don't think
it's worth it for this path.

--
Jens Axboe