linux-kernel - Re: [PATCH 1/2][Untested] ACPI / hotplug: Add demand

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Message-ID: <2270511.t53XC5JBYQ@vostro.rjw.lan>
Date:	Fri, 27 Dec 2013 01:33:30 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Toshi Kani <toshi.kani@...com>,
	Yinghai Lu <yinghai@...nel.org>,
	Zhang Rui <rui.zhang@...el.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Aaron Lu <aaron.lu@...el.com>
Subject: Re: [PATCH 1/2][Untested] ACPI / hotplug: Add demand_offline hotplug profile flag

On Thursday, December 26, 2013 12:10:04 PM Yasuaki Ishimatsu wrote:
> (2013/12/23 23:00), Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > Add a new ACPI hotplug profile flag, demand_offline, such that if
> > set for the given ACPI device object's scan handler, it will cause
> > acpi_scan_hot_remove() to check if that device object's physical
> > companions are offline upfront and fail the hot removal if that
> > is not the case.
> >
> > That flag will be useful to overcome a problem with containers on
> > some system where they can only be hot-removed after some cleanup
> > operations carried out by user space, which needs to be notified
> > of the container hot-removal before the kernel attempts to offline
> > devices in the container.  In those cases the current implementation
> > of acpi_scan_hot_remove() is not sufficient, because it first tries
> > to offline the devices in the container and only if that is
> > suffcessful it tries to offline the container itself.  As a result,
> > the container hot-removal notification is not delivered to user space
> > at the right time.
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> >   drivers/acpi/scan.c     |   41 +++++++++++++++++++++++++++++++++++++----
> >   include/acpi/acpi_bus.h |    3 ++-
> >   2 files changed, 39 insertions(+), 5 deletions(-)
> >
> > Index: linux-pm/drivers/acpi/scan.c
> > ===================================================================
> > --- linux-pm.orig/drivers/acpi/scan.c
> > +++ linux-pm/drivers/acpi/scan.c
> > @@ -126,6 +126,24 @@ acpi_device_modalias_show(struct device
> >   }
> >   static DEVICE_ATTR(modalias, 0444, acpi_device_modalias_show, NULL);
> >
> > +static bool acpi_scan_is_offline(struct acpi_device *adev)
> > +{
> > +	struct acpi_device_physical_node *pn;
> > +	bool offline = true;
> > +
> > +	mutex_lock(&adev->physical_node_lock);
> > +
> > +	list_for_each_entry(pn, &adev->physical_node_list, node)
> 
> > +		if (!pn->dev->offline) {
> 
> Please check pn->dev->bus and pn->dev->bus->offline too as follow:
> 
> 		if (pn->dev->bus && pn->dev->bus->offline &&
> 		    !pn->dev->offline) {
> 
> My container has CPU and Memory and PCI root bridge. PCI root bridge
> does not has offline function (pn->dev->bus->offline). So I cannot offline
> the device and pn->dev->offline of the device is always 0. Therefore,
> following operation always returns -EBUSY even if I offline CPUs and
> all memory sections on a container device.
> 
> echo 0 > /sys/bus/container/devices/ACPI0004:01/online

I see.  We simply can do

	if (device_supports_offline(pn->dev) && !pn->dev->offline) {

there I think.

Thanks,
Rafael

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