linux-kernel - Re: A udev rule to serve the change event of ACPI container?

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Message-ID: <1f1b0229-84c8-f95f-dab4-76588834b6e6@gmail.com>
Date:   Wed, 28 Jun 2017 15:53:16 -0400
From:   YASUAKI ISHIMATSU <yasu.isimatu@...il.com>
To:     joeyli <jlee@...e.com>, linux-acpi@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
        Michal Hocko <mhocko@...e.cz>
Subject: Re: A udev rule to serve the change event of ACPI container?


On 06/26/2017 02:26 AM, joeyli wrote:
> Hi all,
> 
> If ACPI received ejection request for a ACPI container, kernel
> emits KOBJ_CHANGE uevent when it found online children devices
> below the acpi container.
> 
> Base on the description of caa73ea15 kernel patch, user space
> is expected to offline all devices below the container and the
> container itself. Then, user space can finalize the removal of
> the container with the help of its ACPI device object's eject
> attribute in sysfs.
> 
> That means that kernel relies on users space to peform the offline
> and ejection jobs to acpi container and children devices. The
> discussion is here:
> 	https://lkml.org/lkml/2013/11/28/520
> 
> The mail loop didn't explain why the userspace is responsible for
> the whole container offlining. Is it possible to do that transparently
> from the kernel? What's the difference between offlining memory and
> processors which happends without any cleanup and container which
> does essentially the same except it happens at once? 

We don't know what devices mount on the container device. I think
devices mount on the container device are different each vendor's server.

If memory device mounts on the container, memory offline easily fails.
Other devices may have other concerns. So the following udev rule you
write does not work correctly.

I think we need to change offline processing for each device. So currently
the userspace is responsible for the whole container offlining.


Thanks,
Yasuaki Ishimatsu
`

>  
>  - After a couple of years, can we let the container hot-remove
>    process transparently?
>  - Except udev rule, does there have any other mechanism to trigger
>    auto offline/ejection?
> 
> The attached patch is a udev rule that it's used to perform the
> offlien/ejection jobs on user space. I want to send it to systemd.
> 
> Thanks a lot!
> Joey Lee
> 
> From 6c95d4858e0e7c280e490491c1a00c1b5226a029 Mon Sep 17 00:00:00 2001
> From: "Lee, Chun-Yi" <jlee@...e.com>
> Date: Mon, 26 Jun 2017 11:40:03 +0800
> Subject: [PATCH] rules: handle the change event of ACPI container
> 
> Currently the ACPI in kernel emits KOBJ_CHANGE uevent when there
> have online children devices below the acpi container.
> 
> Base on the description of caa73ea15 kernel patch, user space
> is expected to offline all devices below the container and the
> container itself. Then, user space can finalize the removal of
> the container with the help of its ACPI device object's eject
> attribute in sysfs.
> 
> This udev rule can be a default user space application to meet
> kernel's expectations. This rule walks through the sysfs tree
> to trigger the offline of each child device then ejects the
> container.
> 
> The ACPI_CONTAINER_EJECT environoment variable can be used to
> turn off the the ejection logic of container if the ejection
> will be triggered by other ways, e.g. BIOS or other user space
> application.
> 
> Reference: https://lkml.org/lkml/2013/11/28/520
> Cc: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Cc: Michal Hocko <mhocko@...e.cz>
> Signed-off-by: "Lee, Chun-Yi" <jlee@...e.com>
> ---
>  rules/80-acpi-container-hotremove.rules | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>  create mode 100644 rules/80-acpi-container-hotremove.rules
> 
> diff --git a/rules/80-acpi-container-hotremove.rules b/rules/80-acpi-container-hotremove.rules
> new file mode 100644;a
> index 000000000..ef4ceb5fb
> --- /dev/null
> +++ b/rules/80-acpi-container-hotremove.rules
> @@ -0,0 +1,16 @@
> +# do not edit this file, it will be overwritten on update
> +
> +SUBSYSTEM=="container", ACTION=="change", DEVPATH=="*/ACPI0004:??", ENV{ACPI_CONTAINER_EJECT}="1"\
> +RUN+="/bin/sh -c ' \
> +if [ $(cat /sys/$env{DEVPATH}/online) -eq 1 ]; then \
> +        find -L /sys/$env{DEVPATH}/firmware_node/*/physical_node* -maxdepth 1 -name online | \
> +        while read line; do \
> +                if [ $(cat $line) -eq 1 ]; then \
> +                        /bin/echo 0 > $line; \
> +                fi \
> +        done; \
> +        /bin/echo 0 > /sys/$env{DEVPATH}/online; \
> +        if [$env{ACPI_CONTAINER_EJECT} -eq 1] && [ $(cat /sys/$env{DEVPATH}/online) -eq 0 ]; then \
> +                /bin/echo 1 > /sys/$env{DEVPATH}/firmware_node/eject; \
> +        fi \
> +fi
>