Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> writes:
> On Wed, May 24, 2017 at 04:47:28PM +0100, Punit Agrawal wrote:
>> On failing to migrate a page, soft_offline_huge_page() performs the
>> necessary update to the hugepage ref-count. When
>> !hugepage_migration_supported() , unmap_and_move_hugepage() also
>> decrements the page ref-count for the hugepage. The combined behaviour
>> leaves the ref-count in an inconsistent state.
>>
>> This leads to soft lockups when running the overcommitted hugepage test
>> from mce-tests suite.
>>
>> Soft offlining pfn 0x83ed600 at process virtual address 0x400000000000
>> soft offline: 0x83ed600: migration failed 1, type
>> 1fffc00000008008 (uptodate|head)
>> INFO: rcu_preempt detected stalls on CPUs/tasks:
>> Tasks blocked on level-0 rcu_node (CPUs 0-7): P2715
>> (detected by 7, t=5254 jiffies, g=963, c=962, q=321)
>> thugetlb_overco R running task 0 2715 2685 0x00000008
>> Call trace:
>> [<ffff000008089f90>] dump_backtrace+0x0/0x268
>> [<ffff00000808a2d4>] show_stack+0x24/0x30
>> [<ffff000008100d34>] sched_show_task+0x134/0x180
>> [<ffff0000081c90fc>] rcu_print_detail_task_stall_rnp+0x54/0x7c
>> [<ffff00000813cfd4>] rcu_check_callbacks+0xa74/0xb08
>> [<ffff000008143a3c>] update_process_times+0x34/0x60
>> [<ffff0000081550e8>] tick_sched_handle.isra.7+0x38/0x70
>> [<ffff00000815516c>] tick_sched_timer+0x4c/0x98
>> [<ffff0000081442e0>] __hrtimer_run_queues+0xc0/0x300
>> [<ffff000008144fa4>] hrtimer_interrupt+0xac/0x228
>> [<ffff0000089a56d4>] arch_timer_handler_phys+0x3c/0x50
>> [<ffff00000812f1bc>] handle_percpu_devid_irq+0x8c/0x290
>> [<ffff0000081297fc>] generic_handle_irq+0x34/0x50
>> [<ffff000008129f00>] __handle_domain_irq+0x68/0xc0
>> [<ffff0000080816b4>] gic_handle_irq+0x5c/0xb0
>>
>> Fix this by dropping the ref-count decrement in
>> unmap_and_move_hugepage() when !hugepage_migration_supported().
>>
>> Fixes: 32665f2bbfed ("mm/migrate: correct failure handling if !hugepage_migration_support()")
>> Reported-by: Manoj Iyer <manoj.iyer@xxxxxxxxxxxxx>
>> Signed-off-by: Punit Agrawal <punit.agrawal@xxxxxxx>
>> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
>> Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
>> Cc: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>
>> Cc: Christoph Lameter <cl@xxxxxxxxx>
>>
>> --
>> Hi Andrew,
>>
>> We ran into this bug when working towards enabling memory corruption
>> on arm64. The patch was tested on an arm64 platform running v4.12-rc2
>> with the series to enable memory corruption handling[0].
>>
>> Please consider merging as a fix for the 4.12 release.
>>
>> Thanks,
>> Punit
>>
>> [0] https://www.spinics.net/lists/arm-kernel/msg581657.html
>> ---
>> mm/migrate.c | 4 +---
>> 1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index 89a0a1707f4c..187abd1526df 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -1201,10 +1201,8 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
>> * tables or check whether the hugepage is pmd-based or not before
>> * kicking migration.
>> */
>> - if (!hugepage_migration_supported(page_hstate(hpage))) {
>> - putback_active_hugepage(hpage);
>
> Thank you for reporting and suggestion, Punit, Manoj.
>
> Simply dropping this putback_active_hugepage() may resume the failure
> counting issue addressed in 32665f2bbfed, so I would recommend to call
> putback_movable_pages() in failure path in soft_offline_huge_page().
>
> @@ -1600,7 +1600,8 @@ static int soft_offline_huge_page(struct page *page, int flags)
> * only one hugepage pointed to by hpage, so we need not
> * run through the pagelist here.
> */
> - putback_active_hugepage(hpage);
> + if (!list_empty(&pagelist))
> + putback_movable_pages(&pagelist);
> if (ret > 0)
> ret = -EIO;
> } else {
>
> Could you check this works for you?
Using this sequence works as well. I'll send out an update shortly.
Thanks
>
> Thanks,
> Naoya Horiguchi
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