Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=7ed5cb2b73d0c4165c0504c95454fade0c0bf3d9
Commit: 7ed5cb2b73d0c4165c0504c95454fade0c0bf3d9
Parent: e3aded3cc289113c7bc729ef4cb75e56d9aa71be
Author: Hugh Dickins <[EMAIL PROTECTED]>
AuthorDate: Thu Jul 19 01:49:11 2007 -0700
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Thu Jul 19 10:04:50 2007 -0700
Remove nid_lock from alloc_fresh_huge_page
The fix to that race in alloc_fresh_huge_page() which could give an illegal
node ID did not need nid_lock at all: the fix was to replace static int nid
by static int prev_nid and do the work on local int nid. nid_lock did make
sure that racers strictly roundrobin the nodes, but that's not something we
need to enforce strictly. Kill nid_lock.
Signed-off-by: Hugh Dickins <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
mm/hugetlb.c | 10 +++++++---
1 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 15fc7b0..2d7611c 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -104,15 +104,19 @@ static int alloc_fresh_huge_page(void)
{
static int prev_nid;
struct page *page;
- static DEFINE_SPINLOCK(nid_lock);
int nid;
- spin_lock(&nid_lock);
+ /*
+ * Copy static prev_nid to local nid, work on that, then copy it
+ * back to prev_nid afterwards: otherwise there's a window in which
+ * a racer might pass invalid nid MAX_NUMNODES to alloc_pages_node.
+ * But we don't need to use a spin_lock here: it really doesn't
+ * matter if occasionally a racer chooses the same nid as we do.
+ */
nid = next_node(prev_nid, node_online_map);
if (nid == MAX_NUMNODES)
nid = first_node(node_online_map);
prev_nid = nid;
- spin_unlock(&nid_lock);
page = alloc_pages_node(nid, htlb_alloc_mask|__GFP_COMP|__GFP_NOWARN,
HUGETLB_PAGE_ORDER);
-
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