linux-kernel - Re: [PATCH 0/6] improve list

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Date:	Sat, 21 Aug 2010 12:32:49 +0300
From:	Artem Bityutskiy <dedekind1@...il.com>
To:	Don Mullis <don.mullis@...il.com>
Cc:	linux-kernel@...r.kernel.org, David Airlie <airlied@...ux.ie>,
	Dave Chinner <david@...morbit.com>
Subject: Re: [PATCH 0/6] improve list_sort test

On Sun, 2010-08-08 at 12:31 -0700, Don Mullis wrote:
> Yes, invalid 'a' or 'b' pointers would be a bug.  If providing a test
> case is hard, can you say what segment is pointed to?  Into the stack?
> Into address ranges normal for elements, but not now on the list?  Is
> there a pattern to the values returned?  Is it perhaps always the
> first or last callback from a particular call to list_sort()?

You've correctly identified in the the other mail that 'a' and 'b'
sometimes point to the list head. I've just checked this.

> That sometimes a==b is, on the other hand, by design:
> 
> 	/*
> 	 * In worst cases this loop may run many iterations.
> 	 * Continue callbacks to the client even though no
> 	 * element comparison is needed, so the client's cmp()
> 	 * routine can invoke cond_resched() periodically.
> 	 */
> 	(*cmp)(priv, tail, tail);
> 
> Adding a sentence to the function header comment reminding callers
> that they need to be able to handle a==b seems like a good idea.

OK, I'll add it.

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)

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