Message-ID: <49C300D8.5080204@kernel.org>
Date: Fri, 20 Mar 2009 11:35:04 +0900
From: Tejun Heo <tj@kernel.org>
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To: Martin Schwidefsky <schwidefsky@de.ibm.com>
CC: mingo@elte.hu, rusty@rustcorp.com.au, tglx@linutronix.de, x86@kernel.org,
       linux-kernel@vger.kernel.org, hpa@zytor.com,
       Paul Mundt <lethal@linux-sh.org>, rmk@arm.linux.org.uk,
       starvik@axis.com, ralf@linux-mips.org, davem@davemloft.net,
       cooloney@kernel.org, kyle@mcmartin.ca, matthew@wil.cx,
       grundler@parisc-linux.org, takata@linux-m32r.org,
       benh@kernel.crashing.org, rth@twiddle.net, ink@jurassic.park.msu.ru,
       heiko.carstens@de.ibm.com
Subject: Re: [GIT RFC] percpu: use dynamic percpu allocator as the default
 percpu allocator
References: <1236671631-9305-1-git-send-email-tj@kernel.org> <20090316190132.7965a49a@skybase>
In-Reply-To: <20090316190132.7965a49a@skybase>
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Hello, Martin.

Sorry about the delay.

Martin Schwidefsky wrote:
> We do have a problem with #2, the dynamic percpu patches currently
> breaks s390. But the nice thing is that we can now get rid of the GOTENT
> relocation for the percpu symbols. If the code is changed to use
> RELOC_HIDE for the SHIFT_PERCPU_PTR define, everything works just fine.
> Patch attached. Nice works guys.
> 
> Subject: [PATCH] s390: percpu access.
> 
> From: Martin Schwidefsky <schwidefsky@de.ibm.com>
> 
> With the dynamic percpu allocator there is no need anymore to play
> tricks with the GOTENT relocation for the access to the percpu
> symbols. A simple RELOC_HIDE gets the job done.

Hmm... I don't quite get it.  The GOTENT was to work around large
offsets for modules, right?  Can you please explain what changed by
the dynamic percpu allocator?

> +#define SHIFT_PERCPU_PTR(var, offset) RELOC_HIDE(&per_cpu_var(var), (offset))

Hmm... @var already has per_cpu__ prefix when the above macro is
invoked, so doing per_cpu_var() on it again wouldn't work.  If simple
RELOC_HIDE works, you should be able to simply drop the above
definition.  The generic percpu.h will define it.

Thanks.

-- 
tejun
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