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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: Wed, 04 Sep 2002 23:36:20 -0700	[thread overview]
Message-ID: <3D76FB64.7AAB215F@zip.com.au> (raw)
In-Reply-To: E17mooe-00064m-00@starship

Daniel Phillips wrote:
> 
> Hi Marcelo,
> 
> This looks really suspicious, vmscan.c#435:
> 
>         spin_unlock(&pagemap_lru_lock);
>                                                         if (put_page_testzero(page))
>                                                                 __free_pages_ok(page, 0);
>         /* avoid to free a locked page */
>         page_cache_get(page);
> 
>         /* whoops, double free coming */
> 
> I suggest you bump the page count before releasing the lru lock.  The race
> shown above may not in fact be possible, but the current code is fragile.
> 

That's OK.  The page has a ref because of nonzero ->buffers  And it
is locked, which pins page->buffers.

  reply	other threads:[~2002-09-05  6:19 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 [this message]
2002-09-05  6:36   ` Daniel Phillips
2002-09-05  7:07     ` Andrew Morton
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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