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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Stefan Metzmacher <metze@samba.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Andy Lutomirski <luto@kernel.org>, Jens Axboe <axboe@kernel.dk>,
	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: Mon, 3 May 2021 16:48:07 -0700	[thread overview]
Message-ID: <CAHk-=wiR7c-UHh_3Rj-EU8=AbURKchnMFJWW7=5EH=qEUDT8wg@mail.gmail.com> (raw)
In-Reply-To: <12710fda-1732-ee55-9ac1-0df9882aa71b@samba.org>

On Mon, May 3, 2021 at 4:27 PM Stefan Metzmacher <metze@samba.org> wrote:
>
> If I remember correctly gdb showed bogus addresses for the backtraces of the io_threads,
> as some regs where not cleared.

Yeah, so that patch will make the IO thread have the user stack
pointer point to the original user stack, but that stack will
obviously be used by the original thread which means that it will
contain random stuff on it.

Doing a

        childregs->sp = 0;

is probably a good idea for that PF_IO_WORKER case, since it really
doesn't have - or need - a user stack.

Of course, it doesn't really have - or need - any of the other user
registers either, but once you fill in the segment stuff to make gdb
happy, you might as well fill it all in using the same code that the
regular case does.

          Linus

  reply	other threads:[~2021-05-03 23:48 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 [this message]
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
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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