linux-kernel - Re: [PATCH 0/2] Don't show PF_IO

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Message-ID: <ad21da2b-01ea-e77c-70b2-0401059e322b@kernel.dk>
Date:   Thu, 25 Mar 2021 14:40:10 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     io-uring <io-uring@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Stefan Metzmacher <metze@...ba.org>
Subject: Re: [PATCH 0/2] Don't show PF_IO_WORKER in /proc/<pid>/task/

On 3/25/21 2:12 PM, Linus Torvalds wrote:
> On Thu, Mar 25, 2021 at 12:42 PM Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
>>
>> On Thu, Mar 25, 2021 at 12:38 PM Linus Torvalds
>> <torvalds@...ux-foundation.org> wrote:
>>>
>>> I don't know what the gdb logic is, but maybe there's some other
>>> option that makes gdb not react to them?
>>
>> .. maybe we could have a different name for them under the task/
>> subdirectory, for example (not  just the pid)? Although that probably
>> messes up 'ps' too..
> 
> Actually, maybe the right model is to simply make all the io threads
> take signals, and get rid of all the special cases.
> 
> Sure, the signals will never be delivered to user space, but if we
> 
>  - just made the thread loop do "get_signal()" when there are pending signals
> 
>  - allowed ptrace_attach on them
> 
> they'd look pretty much like regular threads that just never do the
> user-space part of signal handling.
> 
> The whole "signals are very special for IO threads" thing has caused
> so many problems, that maybe the solution is simply to _not_ make them
> special?

Just to wrap up the previous one, yes it broke all sorts of things to
make the 'tid' directory different. They just end up being hidden anyway
through that, for both ps and top.

Yes, I do think that maybe it's better to just embrace maybe just
embrace the signals, and have everything just work by default. It's
better than continually trying to make the threads special. I'll see
if there are some demons lurking down that path.

-- 
Jens Axboe