Date: Sun, 20 Jul 2008 15:03:41 +0200
From: Bernhard Walle <bwalle@suse.de>
To: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Vegard Nossum <vegard.nossum@gmail.com>, Greg KH <gregkh@suse.de>,
       Mariusz Kozlowski <m.kozlowski@tuxland.pl>,
       Stephen Rothwell <sfr@canb.auug.org.au>, kernel-testers@vger.kernel.org,
       linux-next@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
       Pekka Enberg <penberg@cs.helsinki.fi>, Ingo Molnar <mingo@elte.hu>,
       Vivek Goyal <vgoyal@redhat.com>, kexec <kexec@lists.infradead.org>
Subject: Re: linux-next: Tree for July 18: warning at kernel/lockdep.c:2068
 trace_hardirqs_on_caller
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* Dave Hansen <dave@linux.vnet.ibm.com> [2008-07-20 02:01]:
>
> It is possible that it could run later.  But, I do know that there are
> at least a couple of these tables (on various arches) that we toss out
> of memory or become unavailable later in boot.  
> 
> I do this this:
> 
>     sysfs: add /sys/firmware/memmap
> 
> is really being done at the wrong level.

I posted that patches multiple times. They were reviewed by the kdump
maintainer and by the kexec maintainer. Why didn't you mention it
*there* that this is the wrong way?

> I don't, for instance, see
> *any* reference to memory hotplug in these patches.

Right. The idea was to add memory hotplugging later. I decided to
create the patch series, get some review, and then fix the rest of the
systems that use memory hot-plugging. So, do you see a problem (in
theory) to add memory and remove memory in that sysfs interface? Of
course the code must be extended to handle modifications in the linked
list afterwards. Yes, I should have made that extension just after the
patch went into tip. Unfortunately, I didn't have time so far.

> Secondly, why don't we just modify the existing /sys/devices/system/memory

Because I didn't know that interface. And because I don't see that
interface on my two systems that I just checked. i386 and x86-64. What
do I have to do to enable that interface?

Does that interface export the *used* memory or just export the memory
that is available? Because exactly that was the reason why I made that
modification -- because kexec needs to know the *available* memory even
if that memory is disabled via 'memmap' or 'mem' command line
parameters.


Bernhard
-- 
Bernhard Walle, SUSE LINUX Products GmbH, Architecture Development
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