mirror of https://lore.kernel.org/lkml/
 help / color / mirror / Atom feed
From: Andrew Morton <akpm@zip.com.au>
To: Daniel Phillips <phillips@arcor.de>
Cc: Marcelo Tosatti <marcelo@conectiva.com.br>, linux-kernel@vger.kernel.org
Subject: Re: Race in shrink_cache
Date: Thu, 05 Sep 2002 00:07:42 -0700	[thread overview]
Message-ID: <3D7702BE.85A5D11D@zip.com.au> (raw)
In-Reply-To: <E17mqFV-00065Y-00@starship>

Daniel Phillips wrote:
> 
> ...
> /*
>  * We must not allow an anon page
>  * with no buffers to be visible on
>  * the LRU, so we unlock the page after
>  * taking the lru lock
>  */
> 
> That is, what's scary about an anon page without buffers?

ooop.  That's an akpm comment.  umm, err..

It solves this BUG:

http://www.cs.helsinki.fi/linux/linux-kernel/2001-37/0594.html

Around the 2.4.10 timeframe, Andrea started putting anon pages
on the LRU.  Then he backed that out, then put it in again.  I
think this comment dates from the time when anon pages were
not on the LRU.  So there's a little window there where the
page is unlocked, we've just dropped its swapdev buffers, the page is
on the LRU and pagemap_lru_lock is not held.

So another CPU came in, found the page on the LRU, saw that it had
no ->mapping and no ->buffers and went BUG.

The fix was to take pagemap_lru_lock before unlocking the page.

The comment is stale.

  reply	other threads:[~2002-09-05  6:50 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-09-05  5:04 Daniel Phillips
2002-09-05  6:36 ` Andrew Morton
2002-09-05  6:36   ` Daniel Phillips
2002-09-05  7:07     ` Andrew Morton [this message]
2002-09-05  7:28       ` Daniel Phillips
2002-09-05  7:53         ` Andrew Morton
2002-09-05 18:41           ` Daniel Phillips
2002-09-05 18:51             ` Andrew Morton
2002-09-05 19:08               ` Daniel Phillips
2002-09-05 19:22                 ` Andrew Morton
2002-09-05 20:00                   ` Daniel Phillips
2002-09-05 13:33     ` Rik van Riel

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=3D7702BE.85A5D11D@zip.com.au \
    --to=akpm@zip.com.au \
    --cc=linux-kernel@vger.kernel.org \
    --cc=marcelo@conectiva.com.br \
    --cc=phillips@arcor.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
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®