Subject: Re: Define __raw_read_lock etc for uniprocessor builds
From: Arjan van de Ven <arjan@infradead.org>
To: joe.korty@ccur.com
Cc: Christoph Hellwig <hch@infradead.org>, mingo@elte.hu, akpm@osdl.org,
       linux-kernel@vger.kernel.org
In-Reply-To: <20060124183808.GA16507@tsunami.ccur.com>
References: <20060124180954.GA14506@tsunami.ccur.com>
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	 <1138127523.2977.70.camel@laptopd505.fenrus.org>
	 <20060124183808.GA16507@tsunami.ccur.com>
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Date: Tue, 24 Jan 2006 19:42:36 +0100
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On Tue, 2006-01-24 at 13:38 -0500, Joe Korty wrote:
> On Tue, Jan 24, 2006 at 07:32:02PM +0100, Arjan van de Ven wrote:
> > On Tue, 2006-01-24 at 13:29 -0500, Joe Korty wrote:
> > > On Tue, Jan 24, 2006 at 06:17:12PM +0000, Christoph Hellwig wrote:
> > > > On Tue, Jan 24, 2006 at 01:09:54PM -0500, Joe Korty wrote:
> > > > > 
> > > > > Make NOPed versions of __raw_read_lock and family available
> > > > > under uniprocessor kernels.
> > > > > 
> > > > > Discovered when compiling a uniprocessor kernel with the
> > > > > fusyn patch applied.
> > > > > 
> > > > > The standard kernel does not use __raw_read_lock etc
> > > > > outside of spinlock.c, which may account for this bug
> > > > > being undiscovered until now.
> > > > 
> > > > No one should call these directly.   Please fix your odd patch instead.
> > > 
> > > Actually the patch calls the _raw version which is #defined to the __raw
> > > version.  So it is doing the correct thing.
> > 
> > no it's not, it has no business calling the _raw version either.
> 
> Nope.
> 
> 1) The _raw_spin_lock family is used everywhere in the kernel.  

no it's not. It's used in a few very special architecture places, and in
the spinlock.c code, and in one place of the scheduler, which is
arguably special.

I don't know what kernel you're looking at.. but it's not a kernel.org
one.


> 2) The _raw versions are intended to be used in places where it is
> known that preemption is already disabled, so that the overhead of
> re-disabling/enabling it can be avoided.

that's not true either. If it was, then the name would have been
different.


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