https://github.com/torvalds/linux
Revision ad33bb04b2a6cee6c1f99fabb15cddbf93ff0433 authored by Andrea Arcangeli on 26 February 2016, 23:19:28 UTC, committed by Linus Torvalds on 27 February 2016, 18:28:52 UTC
pmd_trans_unstable()/pmd_none_or_trans_huge_or_clear_bad() were introduced to locklessy (but atomically) detect when a pmd is a regular (stable) pmd or when the pmd is unstable and can infinitely transition from pmd_none() and pmd_trans_huge() from under us, while only holding the mmap_sem for reading (for writing not). While holding the mmap_sem only for reading, MADV_DONTNEED can run from under us and so before we can assume the pmd to be a regular stable pmd we need to compare it against pmd_none() and pmd_trans_huge() in an atomic way, with pmd_trans_unstable(). The old pmd_trans_huge() left a tiny window for a race. Useful applications are unlikely to notice the difference as doing MADV_DONTNEED concurrently with a page fault would lead to undefined behavior. [akpm@linux-foundation.org: tidy up comment grammar/layout] Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Reported-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 29a9faa
Tip revision: ad33bb04b2a6cee6c1f99fabb15cddbf93ff0433 authored by Andrea Arcangeli on 26 February 2016, 23:19:28 UTC
mm: thp: fix SMP race condition between THP page fault and MADV_DONTNEED
mm: thp: fix SMP race condition between THP page fault and MADV_DONTNEED
Tip revision: ad33bb0
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| .get_maintainer.ignore | -rw-r--r-- | 31 bytes |
| .gitignore | -rw-r--r-- | 1.2 KB |
| .mailmap | -rw-r--r-- | 5.5 KB |
| COPYING | -rw-r--r-- | 18.3 KB |
| CREDITS | -rw-r--r-- | 95.4 KB |
| Kbuild | -rw-r--r-- | 2.6 KB |
| Kconfig | -rw-r--r-- | 252 bytes |
| MAINTAINERS | -rw-r--r-- | 337.2 KB |
| Makefile | -rw-r--r-- | 53.7 KB |
| README | -rw-r--r-- | 18.2 KB |
| REPORTING-BUGS | -rw-r--r-- | 7.3 KB |
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