Linux-Next Archive on lore.kernel.org
 help / color / Atom feed
From: Peter Zijlstra <peterz@infradead.org>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
	Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Linux-Next <linux-next@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Davidlohr Bueso <davidlohr@hp.com>
Subject: Re: linux-next: manual merge of the akpm-current tree with the tip tree
Date: Tue, 14 Jan 2014 14:33:13 +0100
Message-ID: <20140114133313.GZ7572@laptop.programming.kicks-ass.net> (raw)
In-Reply-To: <CAMuHMdUPJ7pu5J6om+j=Tm8xDXhXU3sD4k7ZP6b4Xu-tF+gK2w@mail.gmail.com>

On Tue, Jan 14, 2014 at 02:17:55PM +0100, Geert Uytterhoeven wrote:
> On Tue, Jan 14, 2014 at 1:51 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> > On Tue, Jan 14, 2014 at 03:53:31PM +1100, Stephen Rothwell wrote:
> >> Today's linux-next merge of the akpm-current tree got a conflict in
> >> kernel/futex.c between commit a52b89ebb6d4 ("futexes: Increase hash table
> >> size for better performance") from the tip tree and commit 61beee6c76e5
> >> ("futex: switch to USER_DS for futex test") from the akpm-current tree.
> >>
> >> @@@ -2869,10 -2748,13 +2871,13 @@@
> >>        * implementation, the non-functional ones will return
> >>        * -ENOSYS.
> >>        */
> >> +     fs = get_fs();
> >> +     set_fs(USER_DS);
> >>       if (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT)
> >>               futex_cmpxchg_enabled = 1;
> >> +     set_fs(fs);
> >>
> >
> > This seems terribly broken, the *futex_value*() ops should not need
> > that; they are supposed to access userspace without any of that.
> 
> Why don't they need set_fs(USER_DS)?

Why would they need it? These functions explicitly take a __user pointer
and are expected to do whatever is needed to perform the operation. None
of the other futex bits use USER_DS either.


Furthermore, from the Changelog of:
e4f2dfbb5e92be4e46c0625f4f8eb101110f756f

"   This patch adds that support, but only for uniprocessor machines,
    which is adequate for M68K.  For UP it's enough to disable preemption
    to ensure mutual exclusion (futexes don't need to care about other
    hardware agents), and the mandatory pagefault_disable() does just that.  "

It is wrong to rely on the fact that pagefault_disable() disables
preemption. This is fact not true on -rt.

  reply index

Thread overview: 87+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-01-14  4:53 Stephen Rothwell
2014-01-14  5:04 ` Davidlohr Bueso
2014-01-14 12:51 ` Peter Zijlstra
2014-01-14 13:17   ` Geert Uytterhoeven
2014-01-14 13:33     ` Peter Zijlstra [this message]
2014-01-14 16:19     ` H. Peter Anvin
2014-01-14 15:15   ` H. Peter Anvin
2014-01-14 15:20     ` Geert Uytterhoeven
2014-01-14 15:41       ` Peter Zijlstra
2014-01-14 15:48         ` H. Peter Anvin
  -- strict thread matches above, loose matches on Subject: below --
2019-10-31  5:43 Stephen Rothwell
2019-06-24 10:24 Stephen Rothwell
2019-05-01 11:10 Stephen Rothwell
2019-01-31  4:31 Stephen Rothwell
2018-08-20  4:32 Stephen Rothwell
2018-08-20 19:52 ` Andrew Morton
2018-03-23  5:59 Stephen Rothwell
2017-12-18  5:04 Stephen Rothwell
2017-11-10  4:33 Stephen Rothwell
2017-11-02  7:19 Stephen Rothwell
2017-08-22  6:57 Stephen Rothwell
2017-08-23  6:39 ` Vlastimil Babka
2017-08-11  7:53 Stephen Rothwell
2017-08-11  9:34 ` Peter Zijlstra
2017-08-11 10:48   ` Peter Zijlstra
2017-08-11 11:45   ` Stephen Rothwell
2017-08-11 11:56     ` Ingo Molnar
2017-08-11 12:17       ` Peter Zijlstra
2017-08-11 12:44         ` Ingo Molnar
2017-08-11 13:49           ` Stephen Rothwell
2017-08-11 14:04       ` Peter Zijlstra
2017-08-13  6:06         ` Nadav Amit
2017-08-13 12:50           ` Peter Zijlstra
2017-08-14  3:16             ` Minchan Kim
2017-08-14  5:07               ` Nadav Amit
2017-08-14  5:23                 ` Minchan Kim
2017-08-14  8:38                 ` Minchan Kim
2017-08-14 19:57                   ` Peter Zijlstra
2017-08-16  4:14                     ` Minchan Kim
2017-08-14 19:38                 ` Peter Zijlstra
2017-08-15  7:51                   ` Nadav Amit
2017-08-14  3:09         ` Minchan Kim
2017-08-14 18:54           ` Peter Zijlstra
2017-04-12  6:46 Stephen Rothwell
2017-04-12 20:53 ` Vlastimil Babka
2017-04-20  2:17   ` NeilBrown
2017-03-24  5:25 Stephen Rothwell
2017-02-17  4:40 Stephen Rothwell
2016-11-14  6:08 Stephen Rothwell
2016-07-29  4:14 Stephen Rothwell
2016-06-15  5:23 Stephen Rothwell
2016-06-18 19:39 ` Manfred Spraul
2016-04-29  6:12 Stephen Rothwell
2016-04-29  6:26 ` Ingo Molnar
2016-03-02  5:40 Stephen Rothwell
2016-02-26  5:07 Stephen Rothwell
2016-02-26 21:35 ` Andrew Morton
2016-02-19  4:09 Stephen Rothwell
2016-02-19 15:26 ` Ard Biesheuvel
2015-12-07  8:06 Stephen Rothwell
2015-10-02  4:21 Stephen Rothwell
2015-07-28  6:00 Stephen Rothwell
2015-07-29 17:12 ` Andrea Arcangeli
2015-07-29 17:47   ` Andy Lutomirski
2015-07-29 18:46     ` Thomas Gleixner
2015-07-30 15:38       ` Andrea Arcangeli
2015-07-29 23:06   ` Stephen Rothwell
2015-07-29 23:07     ` Thomas Gleixner
2015-09-07 23:35   ` Stephen Rothwell
2015-09-08 18:11     ` Linus Torvalds
2015-09-08 22:56       ` Stephen Rothwell
2015-09-08 23:03         ` Linus Torvalds
2015-09-08 23:21           ` Andrew Morton
2015-09-16  6:58             ` Geert Uytterhoeven
2015-06-04 12:07 Stephen Rothwell
2015-04-08  8:28 Stephen Rothwell
2015-04-08  8:25 Stephen Rothwell
2014-03-17  9:31 Stephen Rothwell
2014-03-17  9:36 ` Peter Zijlstra
2014-03-19 23:27   ` Andrew Morton
2014-01-07  6:00 Stephen Rothwell
2014-01-07  6:34 ` Tang Chen
2013-11-08  7:48 Stephen Rothwell
2013-11-08 18:58 ` Josh Triplett
2013-11-08 23:20   ` Stephen Rothwell
2013-11-09  0:19     ` Josh Triplett
2013-10-30  6:40 Stephen Rothwell

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20140114133313.GZ7572@laptop.programming.kicks-ass.net \
    --to=peterz@infradead.org \
    --cc=akpm@linux-foundation.org \
    --cc=davidlohr@hp.com \
    --cc=geert@linux-m68k.org \
    --cc=hpa@zytor.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-next@vger.kernel.org \
    --cc=mingo@elte.hu \
    --cc=sfr@canb.auug.org.au \
    --cc=tglx@linutronix.de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Next Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-next/0 linux-next/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-next linux-next/ https://lore.kernel.org/linux-next \
		linux-next@vger.kernel.org
	public-inbox-index linux-next

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-next


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git