diff options
author | Weijie Yang <weijie.yang@samsung.com> | 2015-02-10 14:11:39 -0800 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-02-10 14:30:34 -0800 |
commit | 4c5018ce06c6be292d4ed96cecf2c8dda361a923 (patch) | |
tree | 0e695e86f11df493ad7fcf73daf7fc0fb8ce6c3f /ipc/namespace.c | |
parent | 753162cd849c45580fb5aaa7f3597c81e74e391c (diff) | |
download | linux-4c5018ce06c6be292d4ed96cecf2c8dda361a923.tar.bz2 |
mm/page_alloc.c: place zone_id check before VM_BUG_ON_PAGE check
If the freeing page and its buddy page are not at the same zone, the
current holding zone->lock for the freeing page cann't prevent buddy page
getting allocated, this could trigger VM_BUG_ON_PAGE in page_is_buddy() at
a very tiny chance, such as:
cpu 0: cpu 1:
hold zone_1 lock
check page and it buddy
PageBuddy(buddy) is true hold zone_2 lock
page_order(buddy) == order is true alloc buddy
trigger VM_BUG_ON_PAGE(page_count(buddy) != 0)
zone_1->lock prevents the freeing page getting allocated
zone_2->lock prevents the buddy page getting allocated
they are not the same zone->lock.
If we can't remove the zone_id check statement, it's better handle this
rare race. This patch fixes this by placing the zone_id check before the
VM_BUG_ON_PAGE check.
Signed-off-by: Weijie Yang <weijie.yang@samsung.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc/namespace.c')
0 files changed, 0 insertions, 0 deletions