Re: [PATCH 0/1] pipe: only enable the extra wake_up(rd_wait) when epoll is actually used

[Oleg Nesterov]

On 07/24, Mateusz Guzik wrote:
>
> On Fri, Jul 24, 2026 at 3:58 PM Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
> >
> > This means that io_uring depends on the "nasty semantics" too, io_poll_wake()
> > path should add the task work which calls io_req_post_cqe() every time the new
> > data arrives, even if the pipe was not empty.
> >
>
> well io_uring could set the flag as well in that case? it does not
> inherently mean random select and poll consumers definitely need this.

How? I don't think io_uring can do this. It doesn't even know if the file
is pipe or not. Only file_operations->poll() does know...

__Perhaps__ pipe_poll() could check something like wait->_key & EPOLLET to
detect both epoll/io_uring... Not sure, probably not, I'll try to check later.

Oleg.