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-rw-r--r--include/linux/klist.h3
-rw-r--r--lib/klist.c96
2 files changed, 71 insertions, 28 deletions
diff --git a/include/linux/klist.h b/include/linux/klist.h
index 06c338e..8ea98db 100644
--- a/include/linux/klist.h
+++ b/include/linux/klist.h
@@ -38,7 +38,7 @@ extern void klist_init(struct klist *k, void (*get)(struct klist_node *),
void (*put)(struct klist_node *));
struct klist_node {
- struct klist *n_klist;
+ void *n_klist; /* never access directly */
struct list_head n_node;
struct kref n_ref;
struct completion n_removed;
@@ -57,7 +57,6 @@ extern int klist_node_attached(struct klist_node *n);
struct klist_iter {
struct klist *i_klist;
- struct list_head *i_head;
struct klist_node *i_cur;
};
diff --git a/lib/klist.c b/lib/klist.c
index cca37f9..bbdd301 100644
--- a/lib/klist.c
+++ b/lib/klist.c
@@ -37,6 +37,37 @@
#include <linux/klist.h>
#include <linux/module.h>
+/*
+ * Use the lowest bit of n_klist to mark deleted nodes and exclude
+ * dead ones from iteration.
+ */
+#define KNODE_DEAD 1LU
+#define KNODE_KLIST_MASK ~KNODE_DEAD
+
+static struct klist *knode_klist(struct klist_node *knode)
+{
+ return (struct klist *)
+ ((unsigned long)knode->n_klist & KNODE_KLIST_MASK);
+}
+
+static bool knode_dead(struct klist_node *knode)
+{
+ return (unsigned long)knode->n_klist & KNODE_DEAD;
+}
+
+static void knode_set_klist(struct klist_node *knode, struct klist *klist)
+{
+ knode->n_klist = klist;
+ /* no knode deserves to start its life dead */
+ WARN_ON(knode_dead(knode));
+}
+
+static void knode_kill(struct klist_node *knode)
+{
+ /* and no knode should die twice ever either, see we're very humane */
+ WARN_ON(knode_dead(knode));
+ *(unsigned long *)&knode->n_klist |= KNODE_DEAD;
+}
/**
* klist_init - Initialize a klist structure.
@@ -79,7 +110,7 @@ static void klist_node_init(struct klist *k, struct klist_node *n)
INIT_LIST_HEAD(&n->n_node);
init_completion(&n->n_removed);
kref_init(&n->n_ref);
- n->n_klist = k;
+ knode_set_klist(n, k);
if (k->get)
k->get(n);
}
@@ -115,7 +146,7 @@ EXPORT_SYMBOL_GPL(klist_add_tail);
*/
void klist_add_after(struct klist_node *n, struct klist_node *pos)
{
- struct klist *k = pos->n_klist;
+ struct klist *k = knode_klist(pos);
klist_node_init(k, n);
spin_lock(&k->k_lock);
@@ -131,7 +162,7 @@ EXPORT_SYMBOL_GPL(klist_add_after);
*/
void klist_add_before(struct klist_node *n, struct klist_node *pos)
{
- struct klist *k = pos->n_klist;
+ struct klist *k = knode_klist(pos);
klist_node_init(k, n);
spin_lock(&k->k_lock);
@@ -144,9 +175,10 @@ static void klist_release(struct kref *kref)
{
struct klist_node *n = container_of(kref, struct klist_node, n_ref);
+ WARN_ON(!knode_dead(n));
list_del(&n->n_node);
complete(&n->n_removed);
- n->n_klist = NULL;
+ knode_set_klist(n, NULL);
}
static int klist_dec_and_del(struct klist_node *n)
@@ -154,22 +186,29 @@ static int klist_dec_and_del(struct klist_node *n)
return kref_put(&n->n_ref, klist_release);
}
-/**
- * klist_del - Decrement the reference count of node and try to remove.
- * @n: node we're deleting.
- */
-void klist_del(struct klist_node *n)
+static void klist_put(struct klist_node *n, bool kill)
{
- struct klist *k = n->n_klist;
+ struct klist *k = knode_klist(n);
void (*put)(struct klist_node *) = k->put;
spin_lock(&k->k_lock);
+ if (kill)
+ knode_kill(n);
if (!klist_dec_and_del(n))
put = NULL;
spin_unlock(&k->k_lock);
if (put)
put(n);
}
+
+/**
+ * klist_del - Decrement the reference count of node and try to remove.
+ * @n: node we're deleting.
+ */
+void klist_del(struct klist_node *n)
+{
+ klist_put(n, true);
+}
EXPORT_SYMBOL_GPL(klist_del);
/**
@@ -206,7 +245,6 @@ void klist_iter_init_node(struct klist *k, struct klist_iter *i,
struct klist_node *n)
{
i->i_klist = k;
- i->i_head = &k->k_list;
i->i_cur = n;
if (n)
kref_get(&n->n_ref);
@@ -237,7 +275,7 @@ EXPORT_SYMBOL_GPL(klist_iter_init);
void klist_iter_exit(struct klist_iter *i)
{
if (i->i_cur) {
- klist_del(i->i_cur);
+ klist_put(i->i_cur, false);
i->i_cur = NULL;
}
}
@@ -258,27 +296,33 @@ static struct klist_node *to_klist_node(struct list_head *n)
*/
struct klist_node *klist_next(struct klist_iter *i)
{
- struct list_head *next;
- struct klist_node *lnode = i->i_cur;
- struct klist_node *knode = NULL;
void (*put)(struct klist_node *) = i->i_klist->put;
+ struct klist_node *last = i->i_cur;
+ struct klist_node *next;
spin_lock(&i->i_klist->k_lock);
- if (lnode) {
- next = lnode->n_node.next;
- if (!klist_dec_and_del(lnode))
+
+ if (last) {
+ next = to_klist_node(last->n_node.next);
+ if (!klist_dec_and_del(last))
put = NULL;
} else
- next = i->i_head->next;
+ next = to_klist_node(i->i_klist->k_list.next);
- if (next != i->i_head) {
- knode = to_klist_node(next);
- kref_get(&knode->n_ref);
+ i->i_cur = NULL;
+ while (next != to_klist_node(&i->i_klist->k_list)) {
+ if (likely(!knode_dead(next))) {
+ kref_get(&next->n_ref);
+ i->i_cur = next;
+ break;
+ }
+ next = to_klist_node(next->n_node.next);
}
- i->i_cur = knode;
+
spin_unlock(&i->i_klist->k_lock);
- if (put && lnode)
- put(lnode);
- return knode;
+
+ if (put && last)
+ put(last);
+ return i->i_cur;
}
EXPORT_SYMBOL_GPL(klist_next);

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