linux-kernel - Re: [PATCH 7/10] ACPI / hotplug: Move container-specific code out of the core

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Date:	Fri, 13 Dec 2013 14:17:32 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	"Moore, Robert" <robert.moore@...el.com>,
	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>, Lv Zheng <lv.zheng@...el.com>
Subject: Re: [PATCH 7/10] ACPI / hotplug: Move container-specific code out
 of the core

(2013/12/13 13:56), Rafael J. Wysocki wrote:
> On Friday, December 13, 2013 11:56:32 AM Yasuaki Ishimatsu wrote:
>> Hi Rafael,
>
> Hi,
>
>> Please share your more detailed idea. I started to implement the following
>> idea. But the idea has one problem.
>>
>>>>> The eject work flow can be:
>>>>>      (1) an eject event occurs,
>>>>>      (2) the container "physical" device fails offline in acpi_scan_hot_remove()
>>>>>          emmitting, say, KOBJ_CHANGE for the "physical" device,
>>>>>      (3) user space notices the KOBJ_CHANGE and does the cleanup as needed,
>>>>>      (4) user space changes the "physical" container device flag controlling
>>>>>          offline to 0,
>>>>>      (5) user space uses the sysfs "eject" attribute of the ACPI container object
>>>>>          to finally eject the container,
>>>>>      (6) the offline in acpi_scan_hot_remove() is now successful, because the
>>>>>          flag controlling it has been set to 0 in step (4),
>>>>>      (7) the "physical" container device goes away before executing _EJ0,
>>>>>      (8) the container is ejected.
>>
>> I want to emit KOBJ_CHANGE before offlining devices on container device at (2).
>> But acpi_scan_hot_remove() offlines devices on container device at first.
>> So when offline container device, devices on container has been offlined.
>>
>> Thus the idea cannot fulfill my necessary feature.
>
> Well, in that case we need to treat containers in a special way at the ACPI
> level.  Which is a bit unfortunate so to speak.
>
> To that end I'd try to add a new flag to struct acpi_hotplug_profile, say
> .verify_offline, such that if set, it would cause acpi_scan_hot_remove() to
> check if all of the "physical" companions of the top-level device are offline
> to start with, and if not, it would just emit KOBJ_CHANGE for the companions
> that are not offline and bail out.
>
> So the above algorithm would become:
>
> (1) an eject event occurs,
> (2) acpi_scan_hot_remove() checks the verify_offline flag in the target device's
>      scan_handler structure,
> (3) if set (it would always be set for containers), acpi_scan_hot_remove()
>      checks the status of the target device's "physical" companions; if at least
>      one of them is offline, KOBJ_CHANGE is emitted for that "physical" device,
>      and acpi_scan_hot_remove() returns, [I guess we can just emit KOBJ_CHANGE
>      for the first companion that is not offline at this point.]
> (4) user space notices the KOBJ_CHANGE and does the cleanup as needed; in the
>      process it carries out the offline operation for the container's "physical"
>      companion (there's only one such companion for each container), [That
>      operation for the container itself is trivial, but to succeed it requires
>      all devices below the container to be taken offline in advance.]
> (5) user space uses the sysfs "eject" attribute of the ACPI container object
>      to finally eject the container,
> (6) acpi_scan_hot_remove() is now successful, because the container's "physical"
>      companion is now offline,
> (7) the "physical" container device goes away before executing _EJ0,
> (8) the container is ejected.
>
> I think that should work for you.

This idea seems to same as your previous work.
http://lkml.org/lkml/2013/2/23/97

How about add autoremove flag into acpi_hotplug_profile and check it as follow:

---
  drivers/acpi/scan.c | 5 +++++
  1 file changed, 5 insertions(+)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 5383c81..c43d110 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -409,6 +409,11 @@ static void acpi_hotplug_notify_cb(acpi_handle handle, u32 type, void *data)
  			ost_code = ACPI_OST_SC_EJECT_NOT_SUPPORTED;
  			goto err_out;
  		}
+		if (!handler->hotplug.autoremove) {
+			kobject_uevent(&device->dev.kobj, KOBJ_CHANGE);
+			ost_code = ACPI_OST_SC_EJECT_NON_SPECIFIC_FAILURE;
+			goto err_out;
+		}
  		acpi_evaluate_hotplug_ost(handle, ACPI_NOTIFY_EJECT_REQUEST,
  					  ACPI_OST_SC_EJECT_IN_PROGRESS, NULL);
  		break;

Adding the check into "acpi_hotplug_notify_cb()", user need not change the
flag for removing container device by "sysfs eject".

Thanks,
Yasuaki Ishimatsu

>
> Thanks,
> Rafael
>


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