linux-kernel - Re: [PATCH v3 3/3] acpi,memory-hotplug : add memory offline code to acpi_memory_device

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Date:	Mon, 29 Oct 2012 08:04:32 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Wen Congyang <wency@...fujitsu.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"liuj97@...il.com" <liuj97@...il.com>,
	"len.brown@...el.com" <len.brown@...el.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"kosaki.motohiro@...fujitsu.com" <kosaki.motohiro@...fujitsu.com>,
	"isimatu.yasuaki@...fujitsu.com" <isimatu.yasuaki@...fujitsu.com>,
	"rjw@...k.pl" <rjw@...k.pl>,
	"laijs@...fujitsu.com" <laijs@...fujitsu.com>,
	David Rientjes <rientjes@...gle.com>,
	Christoph Lameter <cl@...ux.com>,
	Minchan Kim <minchan.kim@...il.com>
Subject: Re: [PATCH v3 3/3] acpi,memory-hotplug : add memory offline code to
 acpi_memory_device_remove()

On Mon, 2012-10-29 at 06:16 +0000, Wen Congyang wrote:
> At 10/27/2012 01:14 AM, Toshi Kani Wrote:
> > On Fri, 2012-10-26 at 18:31 +0800, wency@...fujitsu.com wrote:
> >> From: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
> >>
> >> The memory device can be removed by 2 ways:
> >> 1. send eject request by SCI
> >> 2. echo 1 >/sys/bus/pci/devices/PNP0C80:XX/eject
> >>
> >> In the 1st case, acpi_memory_disable_device() will be called.
> >> In the 2nd case, acpi_memory_device_remove() will be called.
> > 
> > Hi Yasuaki, Wen,
> > 
> > Why do you need to have separate code design & implementation for the
> > two cases?  In other words, can the 1st case simply use the same code
> > path of the 2nd case, just like I did for the CPU hot-remove patch
> > below?  It will simplify the code and make the memory notify handler
> > more consistent with other handlers.
> > https://lkml.org/lkml/2012/10/19/456
> 
> Yes, the 1st case can simply reuse the same code of the 2nd case.
> It is another issue. The memory is not offlined and removed in 2nd
> case. This patchset tries to fix this problem. After doing this,
> we can merge the codes for the two cases.
> 
> But there is some bug in the code for 2nd case:
> If offlining memory failed, we don't know such error in 2nd case, and
> the kernel will in a dangerous state: the memory device is poweroffed
> but the kernel is using it.
> 
> We should fix this bug before merging them.

Hi Wen,

Sounds good.  Thanks for the clarification!

-Toshi



> Thanks
> Wen Congyang
> 


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