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From: "Rafael J. Wysocki" <rafael@kernel.org>
Date: Mon, 4 Dec 2017 15:05:05 +0100
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Subject: Re: [PATCH v2 2/5] mm: memory_hotplug: Remove assumption on memory
 state before hotremove
To: Andrea Reale <ar@linux.vnet.ibm.com>
Cc: joeyli <jlee@suse.com>,
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        Will Deacon <will.deacon@arm.com>, qiuxishi@huawei.com,
        Catalin Marinas <catalin.marinas@arm.com>,
        Michal Hocko <mhocko@suse.com>,
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On Mon, Dec 4, 2017 at 12:28 PM, Andrea Reale <ar@linux.vnet.ibm.com> wrote:
> Hi Joey,
>
> and thanks for your comments. Response inline:
>

[cut]

>>
>> So, the BUG() is useful to capture state issue in memory subsystem. But, I
>> understood your concern about the two steps offline/remove from userland.
>>
>> Maybe we should move the BUG() to somewhere but not just remove it. Or if
>> we think that the BUG() is too intense, at least we should print out a error
>> message, and ACPI should checks the return value from subsystem to
>> interrupt memory-hotplug process.
>
> In this patchset, BUG() is moved to acpi_memory_remove_memory(),
> the caller of arch_remove_memory(). However, I agree with Michal, that
> we should not BUG() here but rather halt the hotremove process and print
> some errors.
> Is there any state in ACPI that should be undone in case of hotremove
> errors or we can just stop the process "halfway"?

I have to recall a couple of things before answering this question, so
that may take some time.

Thanks,
Rafael