aboutsummaryrefslogtreecommitdiff
path: root/lib/radix-tree.c
diff options
context:
space:
mode:
authorIngo Molnar <mingo@elte.hu>2010-10-07 09:43:11 +0200
committerIngo Molnar <mingo@elte.hu>2010-10-07 09:43:11 +0200
commitd4f8f217b8a5d5bd02af979650418dca4caec472 (patch)
treeaf047bfa9729c975e24cb7624107574e884d3a57 /lib/radix-tree.c
parent2dfbf4dfbe47a484bae20456c12b40763b9b6af7 (diff)
parent773e3f93577ffb493fb7c39b1a6ecf39b5748e87 (diff)
downloadlinux-linaro-android-d4f8f217b8a5d5bd02af979650418dca4caec472.tar.gz
Merge branch 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu into core/rcu
Diffstat (limited to 'lib/radix-tree.c')
-rw-r--r--lib/radix-tree.c63
1 files changed, 48 insertions, 15 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 0ccbcdf7500..6f412ab4c24 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -174,14 +174,16 @@ static void radix_tree_node_rcu_free(struct rcu_head *head)
{
struct radix_tree_node *node =
container_of(head, struct radix_tree_node, rcu_head);
+ int i;
/*
* must only free zeroed nodes into the slab. radix_tree_shrink
* can leave us with a non-NULL entry in the first slot, so clear
* that here to make sure.
*/
- tag_clear(node, 0, 0);
- tag_clear(node, 1, 0);
+ for (i = 0; i < RADIX_TREE_MAX_TAGS; i++)
+ tag_clear(node, i, 0);
+
node->slots[0] = NULL;
node->count = 0;
@@ -623,6 +625,13 @@ EXPORT_SYMBOL(radix_tree_tag_get);
* also settag. The function stops either after tagging nr_to_tag items or
* after reaching last_index.
*
+ * The tags must be set from the leaf level only and propagated back up the
+ * path to the root. We must do this so that we resolve the full path before
+ * setting any tags on intermediate nodes. If we set tags as we descend, then
+ * we can get to the leaf node and find that the index that has the iftag
+ * set is outside the range we are scanning. This reults in dangling tags and
+ * can lead to problems with later tag operations (e.g. livelocks on lookups).
+ *
* The function returns number of leaves where the tag was set and sets
* *first_indexp to the first unscanned index.
* WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must
@@ -633,9 +642,13 @@ unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
unsigned long nr_to_tag,
unsigned int iftag, unsigned int settag)
{
- unsigned int height = root->height, shift;
- unsigned long tagged = 0, index = *first_indexp;
- struct radix_tree_node *open_slots[height], *slot;
+ unsigned int height = root->height;
+ struct radix_tree_path path[height];
+ struct radix_tree_path *pathp = path;
+ struct radix_tree_node *slot;
+ unsigned int shift;
+ unsigned long tagged = 0;
+ unsigned long index = *first_indexp;
last_index = min(last_index, radix_tree_maxindex(height));
if (index > last_index)
@@ -655,6 +668,13 @@ unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
slot = radix_tree_indirect_to_ptr(root->rnode);
+ /*
+ * we fill the path from (root->height - 2) to 0, leaving the index at
+ * (root->height - 1) as a terminator. Zero the node in the terminator
+ * so that we can use this to end walk loops back up the path.
+ */
+ path[height - 1].node = NULL;
+
for (;;) {
int offset;
@@ -663,17 +683,30 @@ unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
goto next;
if (!tag_get(slot, iftag, offset))
goto next;
+ if (height > 1) {
+ /* Go down one level */
+ height--;
+ shift -= RADIX_TREE_MAP_SHIFT;
+ path[height - 1].node = slot;
+ path[height - 1].offset = offset;
+ slot = slot->slots[offset];
+ continue;
+ }
+
+ /* tag the leaf */
+ tagged++;
tag_set(slot, settag, offset);
- if (height == 1) {
- tagged++;
- goto next;
+
+ /* walk back up the path tagging interior nodes */
+ pathp = &path[0];
+ while (pathp->node) {
+ /* stop if we find a node with the tag already set */
+ if (tag_get(pathp->node, settag, pathp->offset))
+ break;
+ tag_set(pathp->node, settag, pathp->offset);
+ pathp++;
}
- /* Go down one level */
- height--;
- shift -= RADIX_TREE_MAP_SHIFT;
- open_slots[height] = slot;
- slot = slot->slots[offset];
- continue;
+
next:
/* Go to next item at level determined by 'shift' */
index = ((index >> shift) + 1) << shift;
@@ -688,7 +721,7 @@ next:
* last_index is guaranteed to be in the tree, what
* we do below cannot wander astray.
*/
- slot = open_slots[height];
+ slot = path[height - 1].node;
height++;
shift += RADIX_TREE_MAP_SHIFT;
}