linux-kernel - Re: [PATCH 01/12] Use mutex instead of semaphore in driver core

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Date:	Wed, 2 Jan 2008 08:54:53 +0800
From:	"Dave Young" <hidave.darkstar@...il.com>
To:	"Greg KH" <greg@...ah.com>
Cc:	"Greg KH" <gregkh@...e.de>,
	"Peter Zijlstra" <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH 01/12] Use mutex instead of semaphore in driver core

On Dec 30, 2007 1:07 AM, Greg KH <greg@...ah.com> wrote:
>
> On Sat, Dec 29, 2007 at 03:07:30PM +0800, Dave Young wrote:
> > On Dec 29, 2007 1:06 PM, Dave Young <hidave.darkstar@...il.com> wrote:
> > >
> > > On Dec 29, 2007 12:42 PM, Greg KH <gregkh@...e.de> wrote:
> > > > On Sat, Dec 29, 2007 at 10:36:49AM +0800, Dave Young wrote:
> > > > > >
> > > > > The full boot dmesg with lockdep output is out, there's one warnings in it :
> > > >
> > > > Please fix that warning before the next repost of these patches (along
> > > > with fixing the problem of them not being able to be applied and
> > > > successfully built at every point in the series...)
> > > >
> > >
> > > Ok, thanks, I will fix them and repost.
> > >
> >
> > Hi,
> > After digging the code, I feel hard to fix the lockdep warning due to
> > some misterious relationship with usb.
> >
> > Could someone help on this? thanks.
>
> My question back to you is why are you doing this conversion?  Have you
> found that it is needed for something?  Are there problems in the -rt
> kernels that this conversion helps with?  Or is it just a janitorial
> "convert semaphore to mutex" type thing.

Sorry for delay-reply because recently I have little free time.

Mutex is lightweighter than semaphore, the device/class is used
heavily in kernel, so I think the convert would be worth.

>
> If the latter, I would suggest dropping it, as this area is quite
> complex and I think the locking chain too deep at times for a simple
> conversion.

I admit that I did not realize the complex in the lockdep fixing when
writing the patches.

> good luck,
>
> greg k-h
>
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