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.
next prev parent 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 Race in shrink_cache 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
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