On Wed, 24 May 2017, 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
I applied this patch applied to Ubuntu Zesty (4.10) kernel and tested on
QDF2400 platform with mce-test without config migration enabled.
== dmesg ==
[ 91.569358] Soft offlining page 0x1763c00 at 0x400000000000
[ 91.569364] soft offline: 0x1763c00: migration failed 1, type
100000000008008
[ 150.282911] Soft offlining page 0x1763c00 at 0x400000000000
[ 150.282917] soft offline: 0x1763c00: migration failed 1, type
100000000008008
The mce-test failed as expected but did not encounter the soft lockups.
(The test case might have an error it is missing an 'echo' in failure
case.)
$ sudo ./run_hugepage_overcommit.sh
***************************************************************************
Pay attention:
This test checks that hugepage soft-offlining works under overcommitting.
***************************************************************************
-------------------------------------
TestCase ./thugetlb_overcommit 1
FAIL: migration failed.
Unpoisoning.
Num of Executed Test Case: 1 Num of Failed Case: 1
Tested-By: Manoj Iyer <manoj.iyer@xxxxxxxxxxxxx>
Thanks
Manoj Iyer
[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);
+ if (!hugepage_migration_supported(page_hstate(hpage)))
return -ENOSYS;
- }
new_hpage = get_new_page(hpage, private, &result);
if (!new_hpage)
--
============================
Manoj Iyer
Ubuntu/Canonical
ARM Servers - Cloud
============================
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