Re: [PATCH 1/3][-mm] add class_reclassify macro

From: Andrew Morton
Date: Tue May 20 2008 - 15:25:51 EST

On Tue, 20 May 2008 11:36:41 -0600
Matthew Wilcox <matthew@xxxxxx> wrote:

> On Tue, May 20, 2008 at 10:30:45AM -0700, Andrew Morton wrote:
> > Well what are these lockdep warnings? Normally such a warning means that
> > we have a locking bug. I _assume_ that you've determined that the warnings
> > are false-positives?
> Andrew, we already discussed this on the thread you started that you
> then ignored ...


All pertinent information should be in a patch's changelog. Then this
sort of confusion will not occur.

> > The warning which Mariusz Kozlowski discovered ("Subject: Re:
> > 2.6.26-rc2-mm1: possible circular locking dependency detected") was
> > triggered by the "class semaphore to mutex" conversion and it looks
> > like a real bug to me. Would your patch prevent warnings such as that
> > one from being available to us?
> The problem is that you add one type of class which then adds devices
> that are of another class. This is not a bug. My proposal is to give
> each sysfs class its own lock class; Dave's is to only do it for the
> two classes he knows about that do this.

Well that sounds reasonable. I'm not sure that we should introduce
generic-looking helper infrastructure to do it, however.

Anyway I'll happily sit back and let you guys and Greg sort this one out ;)
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