From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Phil Carmody <ext-phil.2.carmody@nokia.com>
Cc: menage@google.com, lizf@cn.fujitsu.com,
containers@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, akpm@linux-foundation.org
Subject: Re: [PATCH 2/2] cgroup: if you list_empty() a head then don't list_del() it
Date: Tue, 15 Mar 2011 18:35:23 +0200 [thread overview]
Message-ID: <20110315163523.GB12170@shutemov.name> (raw)
In-Reply-To: <1300194523-19325-3-git-send-email-ext-phil.2.carmody@nokia.com>
On Tue, Mar 15, 2011 at 03:08:43PM +0200, Phil Carmody wrote:
> list_del() leaves poison in the prev and next pointers. The next
> list_empty() will compare those poisons, and say the list isn't empty.
> Any list operations that assume the node is on a list because of such a
> check will be fooled into dereferencing poison. One needs to INIT the
> node after the del, and fortunately there's already a wrapper for that -
> list_del_init().
>
> Some of the dels are followed by deallocations, so can be ignored,
> and one can be merged with an add to make a move. Apart from that, I
> erred on the side of caution in making nodes list_empty()-queriable.
>
> Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Acked-by: Kirill A. Shutemov <kirill@shutemov.name>
--
Kirill A. Shutemov
next prev parent reply other threads:[~2011-03-15 16:35 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-15 13:08 [PATCH 0/2] suck some poison out of cgroups' linked lists Phil Carmody
2011-03-15 13:08 ` [PATCH 1/2] list.h: add debug version of list_empty Phil Carmody
2011-03-15 13:08 ` [PATCH 2/2] cgroup: if you list_empty() a head then don't list_del() it Phil Carmody
2011-03-15 16:20 ` Paul Menage
2011-03-15 16:35 ` Kirill A. Shutemov [this message]
2011-03-21 23:52 ` [PATCH 1/2] list.h: add debug version of list_empty Andrew Morton
2011-03-22 10:11 ` Phil Carmody
2011-03-22 10:18 ` Kirill A. Shutemov
2011-03-15 13:51 ` [PATCH 0/2] suck some poison out of cgroups' linked lists Christoph Hellwig
2011-03-15 14:01 ` Phil Carmody
2011-03-15 14:12 ` ext Christoph Hellwig
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