linux-kernel - Re: acpi_bus_trim does not detach devices in post order

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Message-ID: <8453998.khIH1RyxM0@vostro.rjw.lan>
Date:	Tue, 06 Aug 2013 16:26:03 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
Cc:	rafael.j.wysocki@...el.com, yinghai@...nel.org, toshi.kani@...com,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: acpi_bus_trim does not detach devices in post order

On Tuesday, August 06, 2013 07:06:37 PM Yasuaki Ishimatsu wrote:
> (2013/08/06 12:07), Yasuaki Ishimatsu wrote:
> > 
> > I acked the following commit but I hit a problem by the commit.
> > So I report it.
> > 
> > commit cecdb193c8d91a42d9489d00618cc3dfff92e55a
> > Author: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > Date:   Tue Jan 15 13:24:02 2013 +0100
> > 
> >      ACPI / scan: Change the implementation of acpi_bus_trim()
> > 
> > Before applying the commit, acpi_bus_trim() detachs devices in post order.
> > 
> > When I hot add memory devices and processor devices by container device
> > in my x86 box, memory devices are added first and processor devices are added
> > second. So I expect that processor devices are removed first and memory
> > devices are removed second when I remove them. And before applying the
> > commit, acpi_bus_trim() did so.
> > 
> > But after appling the commit, acpi_bus_trim() does not detach devices in
> > post order. So when I remove them, memory devices are removed first and
> > processor devices are removed second.
> > 
> > By this, I hit a problem.
> > 
> > In Linux on x86 arch, NUMA node is depend on memory devices. So new NUMA
> > node is created at memory hot adding. Thus when I hot add memory devices and
> > processor devices, we must hot add memory device first. Otherwise, processor
> > devices are not set to correct NUMA node number.
> > 
> > And Linux expects that when removing them, processor devices are removed
> > first before removing memory devices. But acpi_bus_trim() does not do so.
> > By this, NUMA node is not cleared in my x86 box when hot removing memory device
> > and processor devices. When removing memory devices, NUMA node is cleared.
> > But if there are processor devices related with the NUMA node, NUMA node is
> > not be cleared at memory hot removing.
> > 
> > So when I remove them, NUMA node's sysfs file remained as follows:
> 
> I had little mistake. CPU also tries to clear NUMA node.
> But current implementation has bug. So I'll fix it.

Do I understand correctly that with your fix at

https://patchwork.kernel.org/patch/2839298/

the current acpi_bus_trim() implementation will be sufficient?

Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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