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Date: Sun, 8 Aug 2010 13:07:49 -0700
Message-ID: <AANLkTikEN_RBQeOTKxjLp2sud1qyCjFtWSXVXXMc79zw@mail.gmail.com>
Subject: Re: [PATCH 0/6] improve list_sort test
From: Don Mullis <don.mullis@gmail.com>
To: dedekind1@gmail.com
Cc: linux-kernel@vger.kernel.org, David Airlie <airlied@linux.ie>,
        Dave Chinner <david@fromorbit.com>
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On Sun, Aug 8, 2010 at 12:31 PM, Don Mullis <don.mullis@gmail.com> wrote:
> Artem Bityutskiy <dedekind1@gmail.com> writes:
>> Actually, your 'list_sort()' version does have a problem. I found out
>> that it calls 'cmp(priv, a, b)' with 'a = b' sometimes, and in these
>> cases 'a' and 'b' can point to something which is not a valid element of
>> the original list. Probably a senitel or something like that.

Looks like if the original list is a POT in length, the first callback
from line 73 will pass a==b both pointing to the original list_head.
Would you be able to test this fix?

--- linux-2.6.orig/lib/list_sort.c
+++ linux-2.6/lib/list_sort.c
@@ -70,7 +70,7 @@ static void merge_and_restore_back_links
                 * element comparison is needed, so the client's cmp()
                 * routine can invoke cond_resched() periodically.
                 */
-               (*cmp)(priv, tail, tail);
+               (*cmp)(priv, tail->next, tail->next);

                tail->next->prev = tail;
                tail = tail->next;
--
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