linux-kernel - Re: [PATCH 7/7] driver-core : convert semaphore to mutex in struct class

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Date:	Thu, 17 Jan 2008 09:17:35 +0800
From:	"Dave Young" <hidave.darkstar@...il.com>
To:	"Jarek Poplawski" <jarkao2@...il.com>
Cc:	"Greg KH" <gregkh@...e.de>, stefanr@...6.in-berlin.de,
	david-b@...bell.net, stern@...land.harvard.edu,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/7] driver-core : convert semaphore to mutex in struct class

On Jan 16, 2008 4:34 PM, Jarek Poplawski <jarkao2@...il.com> wrote:
> On Wed, Jan 16, 2008 at 09:03:03AM +0800, Dave Young wrote:
> ...
> > The lockdep warining was posted in the below thread, actually, I have
> > built and run this patced kernel for several days, there's no more
> > warnings.
> > http://lkml.org/lkml/2008/1/3/2
>
> Right... But, with something like this:
>
> ... have_some_fun(... cls)
> {
>         mutex_lock_nested(&cls->mutex, SINGLE_DEPTH_NESTING);
>         have_other_fun(cls);
>         mutex_unlock(&cls->mutex);
>
> }
>
> ... have_more_fun(...)
> {
>         ...
>
>         mutex_init(&cls->mutex);
>
>         mutex_lock(&cls->mutex);
>         have_some_fun(cls);
>         mutex_unlock(&cls->mutex);
> }
>
> probably you wouldn't get any lockdep warning too...

Sorry for late reply.
Actually, I don't know much about lockdep. Could you tell how to use
it properly in this scenario?

>
> Of course, if we know all the locking is right such proper lockdep
> annotating shouldn't matter too much. (And of course this could be
> improved later.)
>
> Regards,
> Jarek P.
>
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