From: Jiang Liu <liuj97@gmail.com>
To: Toshi Kani <toshi.kani@hp.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>,
linux-acpi@vger.kernel.org, Hanjun Guo <guohanjun@huawei.com>,
Vasilis Liaskovitis <vasilis.liaskovitis@profitbricks.com>,
isimatu.yasuaki@jp.fujitsu.com, wency@cn.fujitsu.com,
lenb@kernel.org, gregkh@linuxfoundation.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Tang Chen <tangchen@cn.fujitsu.com>
Subject: Re: [RFC PATCH v3 0/3] acpi: Introduce prepare_remove device operation
Date: Fri, 07 Dec 2012 01:01:48 +0800 [thread overview]
Message-ID: <50C0CF7C.7010006@gmail.com> (raw)
In-Reply-To: <1354208592.26955.429.camel@misato.fc.hp.com>
On 11/30/2012 01:03 AM, Toshi Kani wrote:
> On Thu, 2012-11-29 at 11:15 +0100, Rafael J. Wysocki wrote:
>> On Wednesday, November 28, 2012 11:41:36 AM Toshi Kani wrote:
>>> On Wed, 2012-11-28 at 19:05 +0800, Hanjun Guo wrote:
>>>> On 2012/11/24 1:50, 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
>>>>> or SCI-initiated eject of memory devices fail e.g with:
>>>>> echo 1 >/sys/bus/pci/devices/PNP0C80:XX/eject
>>>>>
>>>>> since the ACPI core goes ahead and ejects the device regardless of whether the
>>>>> 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_remove() is changed to handle removal in 2 steps:
>>>>> - preparation for removal i.e. perform part of removal that can fail. Should
>>>>> succeed for device and all its children.
>>>>> - if above step was successfull, proceed to actual device removal
>>>>
>>>> Hi Vasilis,
>>>> We met the same problem when we doing computer node hotplug, It is a good idea
>>>> to introduce prepare_remove before actual device removal.
>>>>
>>>> I think we could do more in prepare_remove, such as rollback. In most cases, we can
>>>> offline most of memory sections except kernel used pages now, should we rollback
>>>> and online the memory sections when prepare_remove failed ?
>>>
>>> I think hot-plug operation should have all-or-nothing semantics. That
>>> is, an operation should either complete successfully, or rollback to the
>>> original state.
>>
>> That's correct.
>>
>>>> As you may know, the ACPI based hotplug framework we are working on already addressed
>>>> this problem, and the way we slove this problem is a bit like yours.
>>>>
>>>> We introduce hp_ops in struct acpi_device_ops:
>>>> struct acpi_device_ops {
>>>> acpi_op_add add;
>>>> acpi_op_remove remove;
>>>> acpi_op_start start;
>>>> acpi_op_bind bind;
>>>> acpi_op_unbind unbind;
>>>> acpi_op_notify notify;
>>>> #ifdef CONFIG_ACPI_HOTPLUG
>>>> struct acpihp_dev_ops *hp_ops;
>>>> #endif /* CONFIG_ACPI_HOTPLUG */
>>>> };
>>>>
>>>> in hp_ops, we divide the prepare_remove into six small steps, that is:
>>>> 1) pre_release(): optional step to mark device going to be removed/busy
>>>> 2) release(): reclaim device from running system
>>>> 3) post_release(): rollback if cancelled by user or error happened
>>>> 4) pre_unconfigure(): optional step to solve possible dependency issue
>>>> 5) unconfigure(): remove devices from running system
>>>> 6) post_unconfigure(): free resources used by devices
>>>>
>>>> In this way, we can easily rollback if error happens.
>>>> How do you think of this solution, any suggestion ? I think we can achieve
>>>> a better way for sharing ideas. :)
>>>
>>> Yes, sharing idea is good. :) I do not know if we need all 6 steps (I
>>> have not looked at all your changes yet..), but in my mind, a hot-plug
>>> operation should be composed with the following 3 phases.
>>>
>>> 1. Validate phase - Verify if the request is a supported operation. All
>>> known restrictions are verified at this phase. For instance, if a
>>> hot-remove request involves kernel memory, it is failed in this phase.
>>> Since this phase makes no change, no rollback is necessary to fail.
>>
>> Actually, we can't do it this way, because the conditions may change between
>> the check and the execution. So the first phase needs to involve execution
>> to some extent, although only as far as it remains reversible.
>
> For memory hot-remove, we can check if the target memory ranges are
> within ZONE_MOVABLE. We should not allow user to change this setup
> during hot-remove operation. Other things may be to check if a target
> node contains cpu0 (until it is supported), the console UART (assuming
> we cannot delete it), etc. We should avoid doing rollback as much as we
> can.
Fengguang from Intel is working on a patchset to hot-remove CPU0(BSP)
on x86 platforms and he has posted several versions. Maybe we could eventually
remove CPU0 on x86.
>
> Thanks,
> -Toshi
>
>
>>> 2. Execute phase - Perform hot-add / hot-remove operation that can be
>>> rolled-back in case of error or cancel.
>>
>> I would just merge 1 and 2.
>>
>>> 3. Commit phase - Perform the final hot-add / hot-remove operation that
>>> cannot be rolled-back. No error / cancel is allowed in this phase. For
>>> instance, eject operation is performed at this phase.
>>
>> Yup.
>>
>> Thanks,
>> Rafael
>>
>>
>
>
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next prev parent reply other threads:[~2012-12-06 17:01 UTC|newest]
Thread overview: 92+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-23 17:50 [RFC PATCH v3 0/3] acpi: Introduce prepare_remove device operation Vasilis Liaskovitis
2012-11-23 17:50 ` [RFC PATCH v3 1/3] acpi: Introduce prepare_remove operation in acpi_device_ops Vasilis Liaskovitis
2012-11-27 0:10 ` Toshi Kani
2012-11-27 18:36 ` Vasilis Liaskovitis
2012-11-27 23:18 ` Rafael J. Wysocki
2012-11-23 17:50 ` [RFC PATCH v3 2/3] acpi_memhotplug: Add prepare_remove operation Vasilis Liaskovitis
2012-11-24 16:23 ` Wen Congyang
2012-11-23 17:50 ` [RFC PATCH v3 3/3] acpi_memhotplug: Allow eject to proceed on rebind scenario Vasilis Liaskovitis
2012-11-24 16:20 ` Wen Congyang
2012-11-26 8:36 ` Vasilis Liaskovitis
2012-11-26 9:11 ` Wen Congyang
2012-11-27 0:19 ` Toshi Kani
2012-11-27 18:32 ` Vasilis Liaskovitis
2012-11-27 22:03 ` Toshi Kani
2012-11-27 23:41 ` Rafael J. Wysocki
2012-11-28 16:01 ` Toshi Kani
2012-11-28 18:40 ` Rafael J. Wysocki
2012-11-28 21:02 ` Toshi Kani
2012-11-28 21:40 ` Rafael J. Wysocki
2012-11-28 21:40 ` Toshi Kani
2012-11-28 22:01 ` Rafael J. Wysocki
2012-11-28 22:04 ` Toshi Kani
2012-11-28 22:21 ` Rafael J. Wysocki
2012-11-28 22:16 ` Toshi Kani
2012-11-28 22:39 ` Rafael J. Wysocki
2012-11-28 22:46 ` Greg KH
2012-11-28 23:05 ` Rafael J. Wysocki
2012-11-28 23:10 ` Greg KH
2012-11-28 23:31 ` Rafael J. Wysocki
2012-11-28 23:49 ` Rafael J. Wysocki
2012-11-29 1:02 ` Toshi Kani
2012-11-29 1:15 ` Toshi Kani
2012-11-29 10:03 ` Rafael J. Wysocki
2012-11-29 11:30 ` Vasilis Liaskovitis
2012-11-29 16:57 ` Rafael J. Wysocki
2012-11-29 17:56 ` Toshi Kani
2012-11-29 20:25 ` Rafael J. Wysocki
2012-11-29 20:38 ` Toshi Kani
2012-11-29 21:23 ` Rafael J. Wysocki
2012-11-29 21:46 ` Toshi Kani
2012-11-29 22:11 ` Rafael J. Wysocki
2012-11-29 23:17 ` Toshi Kani
2012-11-30 0:13 ` Rafael J. Wysocki
2012-11-30 1:09 ` Toshi Kani
2012-11-29 16:43 ` Toshi Kani
2012-11-29 11:04 ` Vasilis Liaskovitis
2012-11-29 17:44 ` Toshi Kani
2012-12-06 9:30 ` Vasilis Liaskovitis
2012-12-06 12:50 ` Rafael J. Wysocki
2012-12-06 15:41 ` Toshi Kani
2012-12-06 20:32 ` Rafael J. Wysocki
2012-11-28 11:05 ` [RFC PATCH v3 0/3] acpi: Introduce prepare_remove device operation Hanjun Guo
2012-11-28 18:41 ` Toshi Kani
2012-11-29 4:48 ` Hanjun Guo
2012-11-29 22:27 ` Toshi Kani
2012-12-03 4:25 ` Hanjun Guo
2012-12-04 0:10 ` Toshi Kani
2012-12-04 9:16 ` Hanjun Guo
2012-12-04 23:23 ` Toshi Kani
2012-12-05 12:10 ` Hanjun Guo
2012-12-05 22:31 ` Toshi Kani
2012-12-06 16:47 ` Jiang Liu
2012-12-07 2:25 ` Toshi Kani
2012-12-06 16:40 ` Jiang Liu
2012-12-06 20:30 ` Rafael J. Wysocki
2012-12-07 2:57 ` Toshi Kani
2012-12-07 5:57 ` Jiang Liu
2012-12-08 1:08 ` Toshi Kani
2012-12-11 14:34 ` Jiang Liu
2012-12-13 14:42 ` Toshi Kani
2012-12-13 15:15 ` Jiang Liu
2012-12-15 1:19 ` Toshi Kani
2012-11-29 10:15 ` Rafael J. Wysocki
2012-11-29 11:36 ` Vasilis Liaskovitis
2012-12-06 16:59 ` Jiang Liu
2012-11-29 17:03 ` Toshi Kani
2012-11-29 20:30 ` Rafael J. Wysocki
2012-11-29 20:39 ` Toshi Kani
2012-11-29 20:56 ` Toshi Kani
2012-11-29 21:25 ` Rafael J. Wysocki
2012-12-06 17:10 ` Jiang Liu
2012-12-06 17:07 ` Jiang Liu
2012-12-06 17:01 ` Jiang Liu [this message]
2012-12-06 16:56 ` Jiang Liu
2012-12-06 16:00 ` Jiang Liu
2012-12-06 16:03 ` Toshi Kani
2012-12-06 16:25 ` Jiang Liu
2012-12-06 16:31 ` Toshi Kani
2012-12-06 16:52 ` Jiang Liu
2012-12-06 17:09 ` Toshi Kani
2012-12-06 17:30 ` Jiang Liu
2012-12-06 17:28 ` Toshi Kani
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