All of lore.kernel.org
 help / color / mirror / Atom feed
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Dave Jones <davej@redhat.com>, Al Viro <viro@zeniv.linux.org.uk>,
	Linux Kernel <linux-kernel@vger.kernel.org>,
	Rik van Riel <riel@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>, Michel Lespinasse <walken@google.com>
Subject: Re: pipe/page fault oddness.
Date: Tue, 30 Sep 2014 08:52:08 -0700	[thread overview]
Message-ID: <CA+55aFynr-Abo_JY1=GGOf9e2tjJvexbX2kVTgD0bkq7BXacJw@mail.gmail.com> (raw)
In-Reply-To: <CA+55aFwxdOBKHwwp7Zq1k19mHCyHYmYqigCVt59AtB-P7Zva1w@mail.gmail.com>

On Mon, Sep 29, 2014 at 9:54 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> Odd. The 0x3b3 offset seems to be the single-byte write of zero, which is
> just the initial probe (aka "fault_in_pages_writeable()").
>
> How *that* could loop, I have no idea. Unless the exception table is broken.
> I'll take another look tomorrow.

Confirmed. It's the second write in fault_in_pages_writeable() (the
one that writes to the "end" pointer).

And there's no loop in software. And in fact, the trace shows that
there is no exception case for the fault either, so the fault is
perfectly successful.

So if it's looping on that fault, what seems to happen is that the
page fault keeps happening.

Can you recreate this? Because if you can, please try to revert commit
e4a1cc56e4d7 ("x86: mm: drop TLB flush from ptep_set_access_flags").
Maybe the TLB has it read-only, and it doesn't get flushed, and the
page fault happens over and over again.

What kind of CPU is the problematic machine? There was some question
about just how architectural the whole "TLB entry causing a page fault
gets invalidated automatically" really is.

                    Linus

  parent reply	other threads:[~2014-09-30 15:52 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-30  3:33 pipe/page fault oddness Dave Jones
2014-09-30  4:27 ` Linus Torvalds
2014-09-30  4:33   ` Dave Jones
     [not found]     ` <CA+55aFwxdOBKHwwp7Zq1k19mHCyHYmYqigCVt59AtB-P7Zva1w@mail.gmail.com>
2014-09-30 15:52       ` Linus Torvalds [this message]
2014-09-30 16:03         ` Rik van Riel
2014-09-30 16:07           ` Dave Jones
2014-09-30 16:26           ` Linus Torvalds
2014-09-30 16:05         ` Dave Jones
2014-09-30 16:10           ` Linus Torvalds
2014-09-30 16:22             ` Dave Jones
2014-09-30 16:40               ` Dave Jones
2014-09-30 16:46                 ` Linus Torvalds
2014-09-30 18:20                   ` Dave Jones
2014-09-30 18:58                     ` Linus Torvalds
2014-10-01  8:19                       ` Hugh Dickins
2014-10-01 16:01                         ` Linus Torvalds
2014-10-01 16:18                           ` Linus Torvalds
2014-10-01 17:29                             ` Rik van Riel
2014-10-02  8:28                               ` Peter Zijlstra
2014-10-01 20:20                             ` Linus Torvalds
2014-10-01 21:09                               ` Rik van Riel
2014-10-01 22:08                               ` Sasha Levin
2014-10-01 22:28                                 ` Chuck Ebbert
2014-10-02  3:32                                   ` Sasha Levin
2014-10-02  8:03                                     ` Chuck Ebbert
2014-10-02 14:49                                       ` Sasha Levin
2014-10-01 22:42                                 ` Linus Torvalds
2014-10-02 14:25                                   ` Kirill A. Shutemov
2014-10-02 16:01                                     ` Linus Torvalds
2014-10-02 16:35                                       ` Kirill A. Shutemov
2014-10-02 15:04                                   ` Sasha Levin
2014-10-02 16:10                                     ` Linus Torvalds
2014-10-03  5:00                                       ` Sasha Levin
2014-10-03 15:43                                         ` Linus Torvalds
2014-10-03 15:58                                           ` Dave Jones
2014-10-03 16:02                                             ` Sasha Levin
2014-10-02 12:45                             ` Mel Gorman
2014-10-06 19:18                               ` Aneesh Kumar K.V
2014-10-07 12:45                                 ` Linus Torvalds
2014-10-08 10:37                                   ` Aneesh Kumar K.V
2014-10-02  8:47                           ` Hugh Dickins
2014-10-02 15:57                             ` Linus Torvalds
2014-09-30  4:35   ` Al Viro

Reply instructions:

You may reply publicly 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='CA+55aFynr-Abo_JY1=GGOf9e2tjJvexbX2kVTgD0bkq7BXacJw@mail.gmail.com' \
    --to=torvalds@linux-foundation.org \
    --cc=davej@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=riel@redhat.com \
    --cc=viro@zeniv.linux.org.uk \
    --cc=walken@google.com \
    /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
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.