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author | Eric Paris <eparis@redhat.com> | 2005-11-21 21:32:28 -0800 |
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committer | Linus Torvalds <torvalds@g5.osdl.org> | 2005-11-22 09:13:43 -0800 |
commit | 0bd0f9fb190a0fc0fb25b764c8b04869711f7657 (patch) | |
tree | 0bd7b58c037b5905cf834f27625bd4e0cbb2f3f2 /Documentation/hpet.txt | |
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 'Documentation/hpet.txt')
0 files changed, 0 insertions, 0 deletions