Re: [PATCH 5/5] io_uring: add IORING_OP_WAITID support

["Arnd Bergmann" <arnd@arndb.de>]

On Tue, Jul 11, 2023, at 22:43, Jens Axboe wrote:
> This adds support for an async version of waitid(2), in a fully async
> version. If an event isn't immediately available, wait for a callback
> to trigger a retry.
>
> The format of the sqe is as follows:
>
> sqe->len		The 'which', the idtype being queried/waited for.
> sqe->fd			The 'pid' (or id) being waited for.
> sqe->file_index		The 'options' being set.
> sqe->addr2		A pointer to siginfo_t, if any, being filled in.
>
> buf_index, add3, and waitid_flags are reserved/unused for now.
> waitid_flags will be used for options for this request type. One
> interesting use case may be to add multi-shot support, so that the
> request stays armed and posts a notification every time a monitored
> process state change occurs.
>
> Note that this does not support rusage, on Arnd's recommendation.
>
> See the waitid(2) man page for details on the arguments.
>
> Signed-off-by: Jens Axboe <axboe@kernel.dk>

Does this require argument conversion for compat tasks?

Even without the rusage argument, I think the siginfo
remains incompatible with 32-bit tasks, unfortunately.

     Arnd