linux-kernel - Re: [PATCH RFC v2 0/3] add cpu physically hotplug driver

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Date:	Mon, 10 Jun 2013 12:04:21 +0800
From:	li guang <lig.fnst@...fujitsu.com>
To:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, Len Brown <lenb@...nel.org>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	platform-driver-x86@...r.kernel.org,
	Andreas Färber <afaerber@...e.de>,
	Igor Mammedov <imammedo@...hat.com>
Subject: Re: [PATCH RFC v2 0/3] add cpu physically hotplug driver

在 2013-06-10一的 12:51 +0900，Yasuaki Ishimatsu写道：
> 2013/06/10 9:36, li guang wrote:
> > Hi, Rafael
> >
> > 在 2013-06-06四的 13:00 +0200，Rafael J. Wysocki写道：
> >> On Thursday, June 06, 2013 09:40:32 AM liguang wrote:
> >>> This patch-set try to support physically hot-plug/unplug
> >>> a cpu automatically, that is:
> >>> if you offline a cpu, it will automatically actually remove
> >>> a cpu, and if you hot-plug a cpu, then it will online this
> >>> cpu automatically.
> >>
> >> No and no.
> >
> > Hmm... are you saying cpu online/offline designed to distinguish
> > with real cpu plug/unplug?
> > but, what the actual usage of online/offline?
> > forgive my foolish.
> >
> >>
> >> Why do you need this?
> >>
> >
> > e.g. for QEMU case, if hot-plug a cpu,
> 
> > we have to online a cpu manually if there's
> > no user space support like udev to do it automatically.
> 
> I could not understand why you do not use udev.
> Please explain in detail.

I did not say I can't use udev now,
just for in case someone can't.

> 
> > and also, I think maybe online/offline should be naturally
> > integrated with real plug/unplug process of CPU.
> 
> I could not understand this explanation too.
> Why do we need it?
> 

actually, I am asking if CPU online/offline have real purpose,
you offline a CPU, then threads can't run on it,
you online a CPU, then threads can run on it,
so, the purpose here is just bouncing threads?
obviously not, any profound historical reasons?

I boldly think maybe online/offline should be integrated into
real plug/unplug process of CPU.

Thanks!

> >
> >>
> >>
> >>> so, offline is just like eject, but eject attribute seems not
> >>> available since recent kernel(can't figure out when), with
> >>> this driver, if allowed, it will trigger a eject cpu process.
> >>> and for automatically online, it was said there are objections,
> >>> don't know the reason, so, send this patch-set boldly.
> >>>
> >>> of course, this approach is for QEMU 's hotplug cpu emulation
> >>> only, but not limited, if someone like to explore ec space to
> >>> implment cpu hot-plug/unplug for real platform please
> >>> feel free to continue.
> >>>
> >>> Li Guang (3)
> >>> 	 drivers/platform/x86: add cpu physically hotplug driver
> >>> 	 ec: add ec space notifier
> >>> 	 cpu_physic_hotplug: register handler for ec space notifier
> >>>
> >>> drivers/acpi/ec.c                         | 32 ++++++++++++++++++++++++++++++++
> >>> drivers/platform/x86/Kconfig              |  8 ++++
> >>> drivers/platform/x86/Makefile             |  1 +
> >>> drivers/platform/x86/cpu_physic_hotplug.c | 90 +++++++++++++++++++++++++++++
> >>> include/linux/acpi.h                      |  2 ++
> >>> 5 files changed, 130 insertions(+), 3 deletions(-)
> >>>   create mode 100644 drivers/platform/x86/cpu_physic_hotplug.c
> >
> >
> > --
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> >
> 
> 


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