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

From: Andrew Morton
Date: Tue May 20 2008 - 13:31:00 EST

On Tue, 20 May 2008 19:05:21 +0800 "Dave Young" <hidave.darkstar@xxxxxxxxx> wrote:

> On Tue, May 20, 2008 at 6:02 PM, Andrew Morton
> <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> > On Tue, 20 May 2008 17:55:54 +0800 Dave Young <hidave.darkstar@xxxxxxxxx> wrote:
> >
> >> Converting class semaphore to mutex cause lockdep warnings due to
> >> class_interface_register/unregister will possible call device_add/del
> >
> > Shouldn't we just fix that?
> Andrew, could you tell more?

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?

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?

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