diff options
author | Eric Paris <eparis@redhat.com> | 2005-11-22 00:32:28 -0500 |
---|---|---|
committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-11-22 12:13:43 -0500 |
commit | 0bd0f9fb190a0fc0fb25b764c8b04869711f7657 (patch) | |
tree | 0bd7b58c037b5905cf834f27625bd4e0cbb2f3f2 /mm/hugetlb.c | |
parent | 5ef897c71a8985b62b7ec320a37376daaad364d0 (diff) |
[PATCH] hugetlb: fix race in set_max_huge_pages for multiple updaters of nr_huge_pages
If there are multiple updaters to /proc/sys/vm/nr_hugepages simultaneously
it is possible for the nr_huge_pages variable to become incorrect. There
is no locking in the set_max_huge_pages function around
alloc_fresh_huge_page which is able to update nr_huge_pages. Two callers
to alloc_fresh_huge_page could race against each other as could a call to
alloc_fresh_huge_page and a call to update_and_free_page. This patch just
expands the area covered by the hugetlb_lock to cover the call into
alloc_fresh_huge_page. I'm not sure how we could say that a sysctl section
is performance critical where more specific locking would be needed.
My reproducer was to run a couple copies of the following script
simultaneously
while [ true ]; do
echo 1000 > /proc/sys/vm/nr_hugepages
echo 500 > /proc/sys/vm/nr_hugepages
echo 750 > /proc/sys/vm/nr_hugepages
echo 100 > /proc/sys/vm/nr_hugepages
echo 0 > /proc/sys/vm/nr_hugepages
done
and then watch /proc/meminfo and eventually you will see things like
HugePages_Total: 100
HugePages_Free: 109
After applying the patch all seemed well.
Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: William Irwin <wli@holomorphy.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm/hugetlb.c')
-rw-r--r-- | mm/hugetlb.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 728e9bda12e..3e52df7c471 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c | |||
@@ -22,6 +22,10 @@ unsigned long max_huge_pages; | |||
22 | static struct list_head hugepage_freelists[MAX_NUMNODES]; | 22 | static struct list_head hugepage_freelists[MAX_NUMNODES]; |
23 | static unsigned int nr_huge_pages_node[MAX_NUMNODES]; | 23 | static unsigned int nr_huge_pages_node[MAX_NUMNODES]; |
24 | static unsigned int free_huge_pages_node[MAX_NUMNODES]; | 24 | static unsigned int free_huge_pages_node[MAX_NUMNODES]; |
25 | |||
26 | /* | ||
27 | * Protects updates to hugepage_freelists, nr_huge_pages, and free_huge_pages | ||
28 | */ | ||
25 | static DEFINE_SPINLOCK(hugetlb_lock); | 29 | static DEFINE_SPINLOCK(hugetlb_lock); |
26 | 30 | ||
27 | static void enqueue_huge_page(struct page *page) | 31 | static void enqueue_huge_page(struct page *page) |
@@ -61,8 +65,10 @@ static struct page *alloc_fresh_huge_page(void) | |||
61 | HUGETLB_PAGE_ORDER); | 65 | HUGETLB_PAGE_ORDER); |
62 | nid = (nid + 1) % num_online_nodes(); | 66 | nid = (nid + 1) % num_online_nodes(); |
63 | if (page) { | 67 | if (page) { |
68 | spin_lock(&hugetlb_lock); | ||
64 | nr_huge_pages++; | 69 | nr_huge_pages++; |
65 | nr_huge_pages_node[page_to_nid(page)]++; | 70 | nr_huge_pages_node[page_to_nid(page)]++; |
71 | spin_unlock(&hugetlb_lock); | ||
66 | } | 72 | } |
67 | return page; | 73 | return page; |
68 | } | 74 | } |