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

Dave Young
2008-01-02T00:55:09Z

On Dec 30, 2007 1:07 AM, Greg KH <greg@kroah.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@gmail.com> wrote:
> > >
> > > On Dec 29, 2007 12:42 PM, Greg KH <gregkh@suse.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
>