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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Mon, 3 May 2021 16:19:35 -0700
Message-ID: <CAHk-=wj+njBWpgFqueHMVk1U8-APxZsgRsrOvhybcBEjspzGSg@mail.gmail.com>
Subject: Re: [PATCH] io_thread/x86: don't reset 'cs', 'ss', 'ds' and 'es'
 registers for io_threads
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Andy Lutomirski <luto@kernel.org>, Jens Axboe <axboe@kernel.dk>,
        Stefan Metzmacher <metze@samba.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        io-uring <io-uring@vger.kernel.org>,
        "the arch/x86 maintainers" <x86@kernel.org>
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On Mon, May 3, 2021 at 4:16 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> These days they really are fully regular user threads, they just don't
> return to user space because they continue to do the IO work that they
> were created for.

IOW, you should think of them as "io_uring does an interface clone()
to generate an async thread, it does the work and then exits".

Now, that's the conceptual thing - in reality one thread can do
multiple async things - but it's the mental image you should have.

Don't think of them as kernel threads. Yes, that's how it started, but
that really ended up being very very painful indeed.

            Linus