The patch titled
Subject: mm: thp: avoid uninitialized variable use
has been added to the -mm tree. Its filename is
mm-thp-use-down_read_trylock-in-khugepaged-to-avoid-long-block-fix-2.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-thp-use-down_read_trylock-in-khugepaged-to-avoid-long-block-fix-2.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-thp-use-down_read_trylock-in-khugepaged-to-avoid-long-block-fix-2.patch
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------------------------------------------------------
From: Arnd Bergmann <arnd@xxxxxxxx>
Subject: mm: thp: avoid uninitialized variable use
When the down_read_trylock() fails, 'vma' has not been initialized yet,
which gcc now warns about:
mm/khugepaged.c: In function 'khugepaged':
mm/khugepaged.c:1659:25: error: 'vma' may be used uninitialized in this function [-Werror=maybe-uninitialized]
Presumably we are not supposed to call find_vma() without the mmap_sem
either, so setting it to NULL for this case seems appropriate.
Link: http://lkml.kernel.org/r/20171215125129.2948634-1-arnd@xxxxxxxx
Fixes: 0951b59acf3a ("mm: thp: use down_read_trylock() in khugepaged to avoid long block")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: "Yang Shi" <yang.s@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/khugepaged.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff -puN mm/khugepaged.c~mm-thp-use-down_read_trylock-in-khugepaged-to-avoid-long-block-fix-2 mm/khugepaged.c
--- a/mm/khugepaged.c~mm-thp-use-down_read_trylock-in-khugepaged-to-avoid-long-block-fix-2
+++ a/mm/khugepaged.c
@@ -1677,11 +1677,10 @@ static unsigned int khugepaged_scan_mm_s
* Don't wait for semaphore (to avoid long wait times). Just move to
* the next mm on the list.
*/
+ vma = NULL;
if (unlikely(!down_read_trylock(&mm->mmap_sem)))
goto breakouterloop_mmap_sem;
- if (unlikely(khugepaged_test_exit(mm)))
- vma = NULL;
- else
+ if (likely(!khugepaged_test_exit(mm)))
vma = find_vma(mm, khugepaged_scan.address);
progress++;
_
Patches currently in -mm which might be from arnd@xxxxxxxx are
mm-thp-use-down_read_trylock-in-khugepaged-to-avoid-long-block-fix-2.patch
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