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SubjectRe: [PATCH v2] memory-hotplug: Clear pgdat which is allocated by bootmem in try_offline_node()
(2014/10/23 4:02), Toshi Kani wrote:
> On Wed, 2014-10-22 at 16:51 +0900, Yasuaki Ishimatsu wrote:
>> When hot adding the same memory after hot removing a memory,
>> the following messages are shown:
>>
>> WARNING: CPU: 20 PID: 6 at mm/page_alloc.c:4968 free_area_init_node+0x3fe/0x426()
>> ...
>> Call Trace:
>> [<...>] dump_stack+0x46/0x58
>> [<...>] warn_slowpath_common+0x81/0xa0
>> [<...>] warn_slowpath_null+0x1a/0x20
>> [<...>] free_area_init_node+0x3fe/0x426
>> [<...>] ? up+0x32/0x50
>> [<...>] hotadd_new_pgdat+0x90/0x110
>> [<...>] add_memory+0xd4/0x200
>> [<...>] acpi_memory_device_add+0x1aa/0x289
>> [<...>] acpi_bus_attach+0xfd/0x204
>> [<...>] ? device_register+0x1e/0x30
>> [<...>] acpi_bus_attach+0x178/0x204
>> [<...>] acpi_bus_scan+0x6a/0x90
>> [<...>] ? acpi_bus_get_status+0x2d/0x5f
>> [<...>] acpi_device_hotplug+0xe8/0x418
>> [<...>] acpi_hotplug_work_fn+0x1f/0x2b
>> [<...>] process_one_work+0x14e/0x3f0
>> [<...>] worker_thread+0x11b/0x510
>> [<...>] ? rescuer_thread+0x350/0x350
>> [<...>] kthread+0xe1/0x100
>> [<...>] ? kthread_create_on_node+0x1b0/0x1b0
>> [<...>] ret_from_fork+0x7c/0xb0
>> [<...>] ? kthread_create_on_node+0x1b0/0x1b0
>>
>> The detaled explanation is as follows:
>>
>> When hot removing memory, pgdat is set to 0 in try_offline_node().
>> But if the pgdat is allocated by bootmem allocator, the clearing
>> step is skipped. And when hot adding the same memory, the uninitialized
>> pgdat is reused. But free_area_init_node() checks wether pgdat is set
>> to zero. As a result, free_area_init_node() hits WARN_ON().
>>
>> This patch clears pgdat which is allocated by bootmem allocator
>> in try_offline_node().
>>
>> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
>
> Thanks for the update. It looks good.
>

> Reviewed-by: Toshi Kani <toshi.kani@hp.com>

Thank you for your review.

Thanks,
Yasuaki Ishimatasu

>
> -Toshi
>
>
>




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