From 172400c69cb0d0d684b7cd75ac75872b3d7c61a1 Mon Sep 17 00:00:00 2001 From: Vlastimil Babka Date: Thu, 5 May 2016 16:22:32 -0700 Subject: [PATCH] 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 Call Trace: schedule+0x35/0x80 schedule_timeout+0x1ac/0x270 wait_for_completion+0xe1/0x120 kthread_stop+0x4f/0x110 kcompactd_stop+0x26/0x40 __offline_pages.constprop.28+0x7e6/0x840 offline_pages+0x11/0x20 memory_block_action+0x73/0x1d0 memory_subsys_offline+0x47/0x60 device_offline+0x86/0xb0 store_mem_state+0xda/0xf0 dev_attr_store+0x18/0x30 sysfs_kf_write+0x37/0x40 kernfs_fop_write+0x11d/0x170 __vfs_write+0x37/0x120 vfs_write+0xa9/0x1a0 SyS_write+0x55/0xc0 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 Tested-by: Reza Arbab Cc: Andrea Arcangeli Cc: "Kirill A. Shutemov" Cc: Rik van Riel Cc: Joonsoo Kim Cc: Mel Gorman Cc: David Rientjes Cc: Michal Hocko Cc: Johannes Weiner Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/compaction.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/compaction.c b/mm/compaction.c index 4a0d4b8ccde8..8fa254043801 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1733,7 +1733,7 @@ void compaction_unregister_node(struct node *node) 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 *pgdat) 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), -- 2.34.1