From: Vlastimil Babka <vbabka@xxxxxxx>
Subject: mm: fix kcompactd hang during memory offlining
Assume memory47 is the last online block left in node1. This will hang:
# echo offline > /sys/devices/system/node/node1/memory47/state
After a couple of minutes, the following pops up in dmesg:
INFO: task bash:957 blocked for more than 120 seconds.
Not tainted 4.6.0-rc6+ #6
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
bash D ffff8800b7adbaf8 0 957 951 0x00000000
ffff8800b7adbaf8 ffff880034d5b880 ffff8800b698d4c0 ffff8800b7adc000
7fffffffffffffff ffff88003381ff10 ffff8800b698d4c0 0000000000180000
ffff8800b7adbb10 ffffffff817be0b5 ffff88003381ff08 ffff8800b7adbbc0
Call Trace:
[<ffffffff817be0b5>] schedule+0x35/0x80
[<ffffffff817c100c>] schedule_timeout+0x1ac/0x270
[<ffffffff810d9750>] ? check_preempt_wakeup+0x100/0x220
[<ffffffff810ce0a0>] ? check_preempt_curr+0x80/0x90
[<ffffffff817bf501>] wait_for_completion+0xe1/0x120
[<ffffffff810cefc0>] ? wake_up_q+0x70/0x70
[<ffffffff810c42ff>] kthread_stop+0x4f/0x110
[<ffffffff811e1046>] kcompactd_stop+0x26/0x40
[<ffffffff817b7a16>] __offline_pages.constprop.28+0x7e6/0x840
[<ffffffff8121ee61>] offline_pages+0x11/0x20
[<ffffffff8151a073>] memory_block_action+0x73/0x1d0
[<ffffffff8151a217>] memory_subsys_offline+0x47/0x60
[<ffffffff81502dc6>] device_offline+0x86/0xb0
[<ffffffff8151a8fa>] store_mem_state+0xda/0xf0
[<ffffffff814ffea8>] dev_attr_store+0x18/0x30
[<ffffffff812c1097>] sysfs_kf_write+0x37/0x40
[<ffffffff812c062d>] kernfs_fop_write+0x11d/0x170
[<ffffffff8123e797>] __vfs_write+0x37/0x120
[<ffffffff8134d1ad>] ? security_file_permission+0x3d/0xc0
[<ffffffff810eed32>] ? percpu_down_read+0x12/0x50
[<ffffffff8123f969>] vfs_write+0xa9/0x1a0
[<ffffffff8134d543>] ? security_file_fcntl+0x43/0x60
[<ffffffff81240dc5>] SyS_write+0x55/0xc0
[<ffffffff817c21b2>] entry_SYSCALL_64_fastpath+0x1a/0xa4
kcompactd is waiting for kcompactd_max_order > 0 when it's woken up to
actually exit. Check kthread_should_stop() to break out of the wait.
Fixes: 698b1b306 ("mm, compaction: introduce kcompactd").
Reported-by: Reza Arbab <arbab@xxxxxxxxxxxxxxxxxx>
Tested-by: Reza Arbab <arbab@xxxxxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff -puN mm/compaction.c~kcompactd-hang-during-memory-offlining mm/compaction.c
--- a/mm/compaction.c~kcompactd-hang-during-memory-offlining
+++ a/mm/compaction.c
@@ -1733,7 +1733,7 @@ void compaction_unregister_node(struct n
static inline bool kcompactd_work_requested(pg_data_t *pgdat)
{
- return pgdat->kcompactd_max_order > 0;
+ return pgdat->kcompactd_max_order > 0 || kthread_should_stop();
}
static bool kcompactd_node_suitable(pg_data_t *pgdat)
@@ -1797,6 +1797,8 @@ static void kcompactd_do_work(pg_data_t
INIT_LIST_HEAD(&cc.freepages);
INIT_LIST_HEAD(&cc.migratepages);
+ if (kthread_should_stop())
+ return;
status = compact_zone(zone, &cc);
if (zone_watermark_ok(zone, cc.order, low_wmark_pages(zone),
_
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
