(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@xxxxxxxxxxxxxx>
Thanks for the update. It looks good.
Reviewed-by: Toshi Kani <toshi.kani@xxxxxx>
Thank you for your review.
Thanks,
Yasuaki Ishimatasu
-Toshi
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