linux-kernel - Re: [RFC PATCH 0/3] acpi: Introduce prepare

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Message-ID: <1647704.U9gX6ykHyh@vostro.rjw.lan>
Date:	Thu, 15 Nov 2012 00:12:55 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Vasilis Liaskovitis <vasilis.liaskovitis@...fitbricks.com>
Cc:	Wen Congyang <wency@...fujitsu.com>, linux-acpi@...r.kernel.org,
	isimatu.yasuaki@...fujitsu.com, lenb@...nel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [RFC PATCH 0/3] acpi: Introduce prepare_remove device operation

On Monday, November 12, 2012 06:20:47 PM Vasilis Liaskovitis wrote:
> On Mon, Nov 12, 2012 at 12:00:55PM +0800, Wen Congyang wrote:
> > At 11/09/2012 02:29 AM, Vasilis Liaskovitis Wrote:
> > > As discussed in
> > > https://patchwork.kernel.org/patch/1581581/
> > > the driver core remove function needs to always succeed. This means we need
> > > to know that the device can be successfully removed before acpi_bus_trim / 
> > > acpi_bus_hot_remove_device are called. This can cause panics when OSPM-initiated
> > > eject (echo 1 > /sys/bus/acpi/devices/PNP/eject) of memory devices fails, since
> > > the ACPI core goes ahead and ejects the device regardless of whether the memory
> > > is still in use or not.
> > > 
> > > For this reason a new acpi_device operation called prepare_remove is introduced.
> > > This operation should be registered for acpi devices whose removal (from kernel
> > > perspective) can fail.  Memory devices fall in this category.
> > > 
> > > acpi_bus_hot_remove_device is changed to handle removal in 2 steps:
> > > - preparation for removal i.e. perform part of removal that can fail outside of
> > >   ACPI core. Should succeed for device and all its children.
> > > - if above step was successfull, proceed to actual ACPI removal
> > 
> > If we unbind the device from the driver, we still need to do preparation. But
> > you don't do it in your patch.
> 
> yes, driver_unbind breaks with the current patchset. I 'll try to fix and
> repost. However, I think this will require a new driver-core wide prepare_remove
> callback (not only acpi-specific). I am not sure that would be acceptable.

However, you can't break driver_unbind either.

Thanks,
Rafael


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