Re: [PATCH 0/2] Don't show PF_IO_WORKER in /proc//task/

Jens Axboe
2021-03-26T00:09:21Z

On 3/25/21 4:37 PM, Linus Torvalds wrote:
> On Thu, Mar 25, 2021 at 2:44 PM Jens Axboe <axboe@kernel.dk> wrote:
>>
>> In the spirit of "let's just try it", I ran with the below patch. With
>> that, I can gdb attach just fine to a test case that creates an io_uring
>> and a regular thread with pthread_create(). The regular thread uses
>> the ring, so you end up with two iou-mgr threads. Attach:
>>
>> [root@archlinux ~]# gdb -p 360
>> [snip gdb noise]
>> Attaching to process 360
>> [New LWP 361]
>> [New LWP 362]
>> [New LWP 363]
> [..]
>
> Looks fairly sane to me.
>
> I think this ends up being the right approach - just the final part
> (famous last words) of "io_uring threads act like normal threads".
>
> Doing it for VM and FS got rid of all the special cases there, and now
> doing it for signal handling gets rid of all these ptrace etc issues.
>
> And the fact that a noticeable part of the patch was removing the
> PF_IO_WORKER tests again looks like a very good sign to me.

I agree, and in fact there are more PF_IO_WORKER checks that can go
too. The patch is just the bare minimum.

> In fact, I think you could now remove all the freezer hacks too -
> because get_signal() will now do the proper try_to_freeze(), so all
> those freezer things are stale as well.

Yep

> Yeah, it's still going to be different in that there's no real user
> space return, and so it will never look _entirely_ like a normal
> thread, but on the whole I really like how this does seem to get rid
> of another batch of special cases.

That's what makes me feel better too. I think was so hung up on the
"never take signals" that it just didn't occur to me to go this
route instead.

I'll send out a clean series.

--
Jens Axboe