From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: linux-mm@kvack.org
Subject: THP race?
Date: Tue, 23 Feb 2016 18:49:50 +0300 [thread overview]
Message-ID: <20160223154950.GA22449@node.shutemov.name> (raw)
Hi Andrea,
I suspect there's race with THP in __handle_mm_fault(). It's pure
theoretical and race window is small, but..
Consider following scenario:
- THP got allocated by other thread just before "pmd_none() &&
__pte_alloc()" check, so pmd_none() is false and we don't
allocate the page table.
- But before pmd_trans_huge() check the page got unmap by
MADV_DONTNEED in other thread.
- At this point we will call pte_offset_map() for pmd which is
pmd_none().
Nothing pleasant would happen after this...
Do you see anything what would prevent this scenario?
--
Kirill A. Shutemov
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next reply other threads:[~2016-02-23 15:49 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-23 15:49 Kirill A. Shutemov [this message]
2016-02-23 18:06 ` THP race? Andrea Arcangeli
2016-02-23 18:18 ` [PATCH 1/1] mm: thp: fix SMP race condition between THP page fault kbuild test robot
2016-02-23 18:21 ` kbuild test robot
2016-02-23 18:27 ` kbuild test robot
2016-02-23 18:38 ` THP race? Kirill A. Shutemov
2016-02-23 19:28 ` Andrea Arcangeli
2016-02-25 18:45 ` Dan Williams
2016-02-26 10:37 ` Kirill A. Shutemov
2016-02-26 14:46 ` Dan Williams
2016-02-23 18:49 ` [PATCH 0/1] " Andrea Arcangeli
2016-02-23 18:49 ` [PATCH 1/1] mm: thp: fix SMP race condition between THP page fault and MADV_DONTNEED Andrea Arcangeli
2016-02-23 21:18 ` Andrew Morton
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