Subject: Re: [-mm PATCH] register_memory/unregister_memory clean ups
From: Badari Pulavarty <pbadari@us.ibm.com>
To: Dave Hansen <haveblue@us.ibm.com>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       lkml <linux-kernel@vger.kernel.org>, greg@kroah.com,
       linux-mm <linux-mm@kvack.org>
In-Reply-To: <1202854520.11188.90.camel@nimitz.home.sr71.net>
References: <20080211114818.74c9dcc7.akpm@linux-foundation.org>
	 <1202765553.25604.12.camel@dyn9047017100.beaverton.ibm.com>
	 <20080212154309.F9DA.Y-GOTO@jp.fujitsu.com>
	 <1202836953.25604.42.camel@dyn9047017100.beaverton.ibm.com>
	 <1202849972.11188.71.camel@nimitz.home.sr71.net>
	 <1202853415.25604.59.camel@dyn9047017100.beaverton.ibm.com>
	 <1202853434.11188.76.camel@nimitz.home.sr71.net>
	 <1202854031.25604.62.camel@dyn9047017100.beaverton.ibm.com>
	 <1202854520.11188.90.camel@nimitz.home.sr71.net>
Content-Type: text/plain
Date: Tue, 12 Feb 2008 14:51:59 -0800
Message-Id: <1202856720.25604.69.camel@dyn9047017100.beaverton.ibm.com>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1977
Lines: 55

On Tue, 2008-02-12 at 14:15 -0800, Dave Hansen wrote:
> On Tue, 2008-02-12 at 14:07 -0800, Badari Pulavarty wrote:
> > On Tue, 2008-02-12 at 13:57 -0800, Dave Hansen wrote:
> > > On Tue, 2008-02-12 at 13:56 -0800, Badari Pulavarty wrote:
> > > > 
> > > > +static void __remove_section(struct zone *zone, unsigned long
> > > > section_nr)
> > > > +{
> > > > +       if (!valid_section_nr(section_nr))
> > > > +               return;
> > > > +
> > > > +       unregister_memory_section(__nr_to_section(section_nr));
> > > > +       sparse_remove_one_section(zone, section_nr);
> > > > +}
> > > 
> > > I do think passing in a mem_section* here is highly superior.  It makes
> > > it impossible to pass a pfn in and not get a warning.
> > > 
> > 
> > Only problem is, I need to hold pgdat_resize_lock() if pass *ms. 
> > If I don't hold the resize_lock, I have to re-evaluate.
> 
> What's wrong with holding the resize lock?  What races, precisely, are
> you trying to avoid?

I was trying to avoid holding resize lock for entire duration of
remove_section(), which includes removing sysfs entries etc. Its
needed only to decode and clear out sectionmap. (I am no longer 
passing pfns).

Whats wrong with passing section_nr ? It simply checks if that
section exists and if so removes sysfs entries and corresponding
sectionmap.  What wrong thing can happen ?

> 
> > And also,
> > I need to pass section_nr for decoding the mem_map anyway :(
> 
> See sparse.c::__section_nr().  It takes a mem_section* and returns a
> section_nr.

I know. It looked like a round about of getting section_nr while
we have that information easily available.

If you are really passionate about passing mem_section*, sure I
can do that :)

Thanks,
Badari

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/