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> -Toshi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>