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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: block: only use __set_current_state() for polled IO
Date: Wed, 2 Jan 2019 10:11:39 -0800	[thread overview]
Message-ID: <CAHk-=whcmNjH+3pP_tgKbxe3iNu20eVVxfDyVXrKsNf7HiR0WA@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=wicNcMhY_YCkT5Nsdcxake8x+sfYUByvbhTzp2v-LWjeA@mail.gmail.com>

On Wed, Jan 2, 2019 at 10:07 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> Stop this craziness. The optimization is garbage. If you want to save
> 15 cycles, get rid of code, don't add new code in an area where the
> block maintainers have already shown that they can't get it right.

Side note: that argument is further strengthened by a very simple
observation: if the code isn't going to sleep, then the whole state
setting is entirely and utterly pointless.

So code like this:

+                       if (is_poll)
+                               __set_current_state(TASK_UNINTERRUPTIBLE);

is *FUNDAMENTAL* garbage.

Seriously, stop playing stupid games. You're doing things wrong.

I'm doing to revert that buggy commit, and I will not pull any crazy
code that tries to redo this kind of completely broken code.

                 Linus

  parent reply	other threads:[~2019-01-02 18:12 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-02 17:55 block: only use __set_current_state() for polled IO Jens Axboe
2019-01-02 18:07 ` Linus Torvalds
2019-01-02 18:10   ` Jens Axboe
2019-01-02 18:11   ` Linus Torvalds [this message]
2019-01-02 18:14     ` Jens Axboe
2019-01-02 18:55       ` Linus Torvalds
2019-01-02 18:59         ` Jens Axboe

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