diff options
| author | Kirill A. Shutemov <kirill.shutemov@linux.intel.com> | 2017-04-14 00:56:20 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-04-14 04:24:20 +0300 |
| commit | ced108037c2aa542b3ed8b7afd1576064ad1362a (patch) | |
| tree | 9bbfcea14b7f7098f667e213a6cc5851e7adc105 /block/compat_ioctl.c | |
| parent | 0a85e51d37645e9ce57e5e1a30859e07810ed07c (diff) | |
| download | linux-ced108037c2aa542b3ed8b7afd1576064ad1362a.tar.xz | |
thp: fix MADV_DONTNEED vs. numa balancing race
In case prot_numa, we are under down_read(mmap_sem). It's critical to
not clear pmd intermittently to avoid race with MADV_DONTNEED which is
also under down_read(mmap_sem):
CPU0: CPU1:
change_huge_pmd(prot_numa=1)
pmdp_huge_get_and_clear_notify()
madvise_dontneed()
zap_pmd_range()
pmd_trans_huge(*pmd) == 0 (without ptl)
// skip the pmd
set_pmd_at();
// pmd is re-established
The race makes MADV_DONTNEED miss the huge pmd and don't clear it
which may break userspace.
Found by code analysis, never saw triggered.
Link: http://lkml.kernel.org/r/20170302151034.27829-3-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'block/compat_ioctl.c')
0 files changed, 0 insertions, 0 deletions