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Message-ID: <5BE44FDB.6040303@huawei.com>
Date: Thu, 8 Nov 2018 23:01:47 +0800
From: zhong jiang <zhongjiang@huawei.com>
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Subject: [Question] There is a thp count left when the process exits
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Sender: owner-linux-mm@kvack.org
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To: Michal Hocko <mhocko@kernel.org>, Anshuman Khandual <khandual@linux.vnet.ibm.com>, Matthew Wilcox <willy@infradead.org>, Andrea
 Arcangeli <aarcange@redhat.com>, David Rientjes <rientjes@google.com>, Vlastimil Babka <vbabka@suse.cz>, "'Kirill A . Shutemov'" <kirill.shutemov@linux.intel.com>
Cc: Linux Memory Management List <linux-mm@kvack.org>

Hi, 

Recently,  I hit  the following issue in linux 3.10 stable.  and hard to recur.

bad pmd ffff880c13ecea80(80000017b16000e7)

Call Trace:
  [<ffffffff8164195f>] dump_stack+0x19/0x1b
  [<ffffffff8107b230>] warn_slowpath_common+0x70/0xb0
  [<ffffffff8107b37a>] warn_slowpath_null+0x1a/0x20
  [<ffffffff811a2b86>] exit_mmap+0x196/0x1a0
  [<ffffffff810782e7>] mmput+0x67/0xf0
  [<ffffffff81081b2c>] do_exit+0x28c/0xa60
  [<ffffffff810a9dc0>] ? hrtimer_get_res+0x50/0x50
  [<ffffffff8108237f>] do_group_exit+0x3f/0xa0
  [<ffffffff81093240>] get_signal_to_deliver+0x1d0/0x6d0
  [<ffffffff81014427>] do_signal+0x57/0x6b0
  [<ffffffff810e4f92>] ? futex_wait_queue_me+0xa2/0x120
  [<ffffffff8164d323>] ? __do_page_fault+0x183/0x470
  [<ffffffff81014adf>] do_notify_resume+0x5f/0xb0
  [<ffffffff816520bd>] int_signal+0x12/0x17

BUG: Bad rss-counter state mm:ffff8820136b5dc0 idx:1 val:512

The pmd entry show that it is still a thp. but It fails to check and clear the pmd.
hence,   page fault will produce a new page for pmd when accessing the page,
which thp count will reduplicative increase.

Thanks,
zhong jiang