linux-kernel - Re: [RFC patch] extable and module add object is static

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Message-ID: <20100329031804.GA12788@Krystal>
Date:	Sun, 28 Mar 2010 23:18:04 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	akpm@...ux-foundation.org, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org, dipankar@...ibm.com,
	josh@...htriplett.org, dvhltc@...ibm.com, niv@...ibm.com,
	tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
	Valdis.Kletnieks@...edu, dhowells@...hat.com,
	eric.dumazet@...il.com, adobriyan@...il.com,
	Tony Luck <tony.luck@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>
Subject: Re: [RFC patch] extable and module add object is static

* Lai Jiangshan (laijs@...fujitsu.com) wrote:
> Mathieu Desnoyers wrote:
> > +static int core_object_is_static(void *obj)
> > +{
> [...]
> > +	if (addr >= (unsigned long)__per_cpu_start &&
> > +	    addr <= (unsigned long)__per_cpu_end)
> > +		return 1;
> 
> This may only correct for UP.
> You may need arch-special codes for SMP.
> 

looking at include/linux/percpu.h:

#ifndef PERCPU_ENOUGH_ROOM
#define PERCPU_ENOUGH_ROOM                                              \
        (ALIGN(__per_cpu_end - __per_cpu_start, SMP_CACHE_BYTES) +      \
         PERCPU_MODULE_RESERVE)
#endif

I was under the impression that most architectures were keeping their per-cpu
data within the __per_cpu_start .. __per_cpu_end range. But I see that ia64
is the only one to redefine PERCPU_ENOUGH_ROOM. I'm not sure if it can be a
problem. Is that what you had in mind ?

(adding Tony and Fenghua in CC so they can confirm)

Thanks,

Mathieu


-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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