linux-kernel - Re: [PATCH 1/2] lib: more scalable list

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Date:	Thu, 21 Jan 2010 08:34:40 -0800
From:	Don Mullis <don.mullis@...il.com>
To:	dedekind@...radead.org
Cc:	Dave Chinner <david@...morbit.com>, linux-kernel@...r.kernel.org,
	airlied@...hat.com, andi@...stfloor.org
Subject: Re: [PATCH 1/2] lib: more scalable list_sort()

Artem Bityutskiy <dedekind@...radead.org> writes:

> On Thu, 2010-01-21 at 20:54 +1100, Dave Chinner wrote:
>> On Thu, Jan 21, 2010 at 11:22:55AM +0200, Artem Bityutskiy wrote:
>> > 
>> > Could you please add a debugging function which would be compiled-out
>> > normally, and which would check that on the output 'list_sort()' gives
>> > really sorted list, and number of elements in the list stays the same.
>> > You'd call this function before returning from list_sort(). Something
>> > like:
>> > 
>> > #ifdef DEBUG_LIST_SORT
>> > static int list_check(void *priv, struct list_head *head,
>> >                       int (*cmp)(void *priv, struct list_head *a,
>> >                                  struct list_head *b))
>> > {
>> >    /* Checking */
>> > }
>> > #else
>> > #define list_check(priv, head, cmp) 0
>> > #endif
>> > 
>> > This will provide more confidence in the algorithm correctness for
>> > everyone who modifies 'list_sort()'.
>> 
>> I'd suggest the same method as employed in lib/sort.c - a
>> simple userspace program that verifies correct operation is included
>> in lib/sort.c....
>
> Yeah, that's also an option.

Okay. The regression test in lib/sort.c is kernel-space, run once at
boot. I'd like to do something similar for lib/list_sort.c, conditioned
on DEBUG_LIST_SORT. I would extend the testing to verify stability as
well as sort order and number of elements.
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