linux-kernel - Re: 2.6.27-rc4-git1: Reported regressions from 2.6.26

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Message-ID: <19f34abd0808241143t6f5239d7o679135e9e974fe63@mail.gmail.com>
Date:	Sun, 24 Aug 2008 20:43:45 +0200
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	"Linus Torvalds" <torvalds@...ux-foundation.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	"Daniel J Blueman" <daniel.blueman@...il.com>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"Adrian Bunk" <bunk@...nel.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Natalie Protasevich" <protasnb@...il.com>,
	"Kernel Testers List" <kernel-testers@...r.kernel.org>
Subject: Re: 2.6.27-rc4-git1: Reported regressions from 2.6.26

On Sun, Aug 24, 2008 at 8:03 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
>
> On Sat, 23 Aug 2008, Rafael J. Wysocki wrote:
>>
>> Bug-Entry     : http://bugzilla.kernel.org/show_bug.cgi?id=11410
>> Subject               : SLUB list_lock vs obj_hash.lock...
>> Submitter     : Daniel J Blueman <daniel.blueman@...il.com>
>> Date          : 2008-08-22 21:48 (2 days old)
>> References    : http://marc.info/?l=linux-kernel&m=121944176609042&w=4
>
> This one now has a suggested patch for Daniel to try from Vegard, but no
> reply yet:
>
>        http://marc.info/?l=linux-kernel&m=121946972307110&w=4
>

Hi!

> Vegard, I think your patch is a bit odd, though. The result of your patch
> is
>
>  - first loop:
>
>        hlist_for_each_entry_safe(obj, node, tmp, &db->list, node) {
>                hlist_del(&obj->node);
>                hlist_add_head(&obj->node, &freelist);
>        }
>
>   and quite frankly, I don't see what the difference between that and a
>   something like a simple
>
>        struct hlist_node *first = bd->list.first;
>        if (first) {
>                bd->list.first = NULL;
>                first->pprev = &first;
>        }
>
>   really is?
>
> I dunno. We don't have list splicing ops for the hlist things.

Hm.

I haven't really used the hlists before, so my first instinct was to
do what is obvious. That's also why I put the XXX comment. Other than
that, I guess open-coding list ops is also not very good programming
practice? :-)

But... feel free to submit your own patch. Oh, what am I saying.


Vegard

-- 
"The animistic metaphor of the bug that maliciously sneaked in while
the programmer was not looking is intellectually dishonest as it
disguises that the error is the programmer's own creation."
	-- E. W. Dijkstra, EWD1036
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