linux-kernel - Re: [2/7, v9] NUMA Hotplug Emulator: Add numa=possible option

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Date:	Wed, 22 Dec 2010 17:14:13 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Haicheng Li <haicheng.li@...ux.intel.com>, lethal@...ux-sh.org,
	Andi Kleen <ak@...ux.intel.com>, shaohui.zheng@...ux.intel.com,
	dave@...ux.vnet.ibm.com, Greg KH <gregkh@...e.de>
Subject: Re: [2/7, v9] NUMA Hotplug Emulator: Add numa=possible option

On Wed, 22 Dec 2010, Andrew Morton wrote:

> > @@ -646,6 +647,15 @@ void __init initmem_init(unsigned long start_pfn, unsigned long last_pfn,
> >  		numa_set_node(i, 0);
> >  	memblock_x86_register_active_regions(0, start_pfn, last_pfn);
> >  	setup_node_bootmem(0, start_pfn << PAGE_SHIFT, last_pfn << PAGE_SHIFT);
> > +out: __maybe_unused
> 
> hm, I didn't know you could do that with labels.
> 
> Does it work?
> 

Yeah, it's equivalent to __attribute__((unused)) and according to the gcc 
manual section 6.30:

	In GNU C, an attribute specifier list may appear after the colon 
	following a label, other than a case or default label. The only 
	attribute it makes sense to use after a label is unused. This 
	feature is intended for code generated by programs which contains 
	labels that may be unused but which is compiled with ‘-Wall’. It 
	would not normally be appropriate to use in it human-written code, 
	though it could be useful in cases where the code that jumps to 
	the label is contained within an #ifdef conditional.

I used it because I knew I wouldn't get away with putting a label inside 
an #ifdef :)

> > +	for (i = 0; i < numa_possible_nodes; i++) {
> > +		int nid;
> > +
> > +		nid = first_unset_node(node_possible_map);
> > +		if (nid == MAX_NUMNODES)
> > +			break;
> > +		node_set(nid, node_possible_map);
> > +	}
> >  }
> >  
> >  unsigned long __init numa_free_all_bootmem(void)