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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Olivier Langlois <olivier@trillion01.com>
Cc: Jens Axboe <axboe@kernel.dk>, Stefan Metzmacher <metze@samba.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Andy Lutomirski <luto@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	io-uring <io-uring@vger.kernel.org>,
	"the arch/x86 maintainers" <x86@kernel.org>
Subject: Re: [PATCH] io_thread/x86: don't reset 'cs', 'ss', 'ds' and 'es' registers for io_threads
Date: Tue, 25 May 2021 10:23:39 -1000	[thread overview]
Message-ID: <CAHk-=whZZ-g6qJ1Epox6c-_U-jSs+syA_7a8QKQkxZaudXXR_Q@mail.gmail.com> (raw)
In-Reply-To: <d9a12052074ba194fe0764c932603a5f85c5445a.camel@trillion01.com>

On Tue, May 25, 2021 at 9:40 AM Olivier Langlois <olivier@trillion01.com> wrote:
>
> If I look in the create_io_thread() function, I can see that CLONE_VM
> isn't set...

That would indeed be horribly buggy, but I'm not seeing it:

                .flags          = ((lower_32_bits(flags) | CLONE_VM |
                                    CLONE_UNTRACED) & ~CSIGNAL),

Yeah, it has that odd "first create 'flags' without the CLONE_VM, but
that is only used for that

        lower_32_bits(flags)

thing, and then we explicitly add CLONE_VM in there in the actual
kernel_clone_args.

It's because of how 'kernel_thread()' is written (that has historical
reasons), and the oddity is copied from there.

           Linus

  parent reply	other threads:[~2021-05-25 20:24 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <8735v3ex3h.ffs@nanos.tec.linutronix.de>
2021-05-03 16:05 ` [PATCH] io_thread/x86: don't reset 'cs', 'ss', 'ds' and 'es' registers for io_threads Andy Lutomirski
2021-05-03 19:14   ` Linus Torvalds
2021-05-03 20:15     ` Andy Lutomirski
2021-05-03 20:21       ` Andy Lutomirski
2021-05-03 20:37       ` Linus Torvalds
2021-05-03 21:26         ` Jens Axboe
2021-05-03 21:49           ` Andy Lutomirski
2021-05-03 22:08             ` Linus Torvalds
2021-05-03 22:56               ` Thomas Gleixner
2021-05-03 23:15                 ` Andy Lutomirski
2021-05-03 23:16                 ` Linus Torvalds
2021-05-03 23:19                   ` Linus Torvalds
2021-05-03 23:27                   ` Stefan Metzmacher
2021-05-03 23:48                     ` Linus Torvalds
2021-05-04  2:50                       ` Jens Axboe
2021-05-04 11:39                         ` Stefan Metzmacher
2021-05-04 15:53                           ` Linus Torvalds
2021-05-12  4:24                         ` Olivier Langlois
2021-05-12 17:44                           ` Linus Torvalds
2021-05-12 20:55                             ` Jens Axboe
2021-05-20  4:13                               ` Olivier Langlois
2021-05-21  7:31                                 ` Olivier Langlois
2021-05-25 19:39                                   ` Olivier Langlois
2021-05-25 19:45                                     ` Olivier Langlois
2021-05-25 19:52                                     ` Jens Axboe
2021-05-25 20:23                                     ` Linus Torvalds [this message]
2021-05-04  8:22                       ` David Laight
2021-05-04  0:01                   ` Andy Lutomirski
2021-05-04  8:39     ` Peter Zijlstra
2021-05-04 15:35       ` Borislav Petkov
2021-05-04 15:55         ` Simon Marchi
2021-05-05 11:29           ` Stefan Metzmacher
2021-05-05 21:59             ` Simon Marchi
2021-05-05 22:11               ` Andy Lutomirski
2021-05-05 23:12                 ` Borislav Petkov
2021-05-05 23:22                   ` Andy Lutomirski
2021-05-06  1:04                 ` Simon Marchi
2021-05-06 15:11                   ` Andy Lutomirski
2021-05-06  9:47                 ` David Laight
2021-05-06  9:53                   ` David Laight
2021-05-05 22:21               ` Stefan Metzmacher
2021-05-05 23:15                 ` Simon Marchi
2021-04-11 15:27 Stefan Metzmacher
2021-04-14 21:28 ` Stefan Metzmacher

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