This patch is from Nathan Lynch <[EMAIL PROTECTED]>.
This changes struct device_node and associated code to use the kref
api for object refcounting and freeing. I've given it some testing on
pSeries with cpu add/remove and verified that the release function
works. The change is somewhat cosmetic but it does make the code
easier to understand... at least I think so =)
The only real change is that the refcount on all device_nodes is
initialized at 1, and the device node is freed when the refcount
reaches 0 (of_remove_node has the extra "put" to ensure that this
happens). This lets us get rid of the OF_STALE flag and macros in
prom.h.
Signed-off-by: Nathan Lynch <[EMAIL PROTECTED]>
Signed-off-by: Paul Mackerras <[EMAIL PROTECTED]>
diff -urN linux-2.5/arch/ppc64/kernel/prom.c test/arch/ppc64/kernel/prom.c
--- linux-2.5/arch/ppc64/kernel/prom.c 2005-01-22 09:25:41.000000000 +1100
+++ test/arch/ppc64/kernel/prom.c 2005-01-22 20:52:35.000000000 +1100
@@ -717,6 +717,7 @@
dad->next->sibling = np;
dad->next = np;
}
+ kref_init(&np->kref);
}
while(1) {
u32 sz, noff;
@@ -1475,24 +1476,31 @@
* @node: Node to inc refcount, NULL is supported to
* simplify writing of callers
*
- * Returns the node itself or NULL if gone.
+ * Returns node.
*/
struct device_node *of_node_get(struct device_node *node)
{
- if (node && !OF_IS_STALE(node)) {
- atomic_inc(&node->_users);
- return node;
- }
- return NULL;
+ if (node)
+ kref_get(&node->kref);
+ return node;
}
EXPORT_SYMBOL(of_node_get);
+static inline struct device_node * kref_to_device_node(struct kref *kref)
+{
+ return container_of(kref, struct device_node, kref);
+}
+
/**
- * of_node_cleanup - release a dynamically allocated node
- * @arg: Node to be released
+ * of_node_release - release a dynamically allocated node
+ * @kref: kref element of the node to be released
+ *
+ * In of_node_put() this function is passed to kref_put()
+ * as the destructor.
*/
-static void of_node_cleanup(struct device_node *node)
+static void of_node_release(struct kref *kref)
{
+ struct device_node *node = kref_to_device_node(kref);
struct property *prop = node->properties;
if (!OF_IS_DYNAMIC(node))
@@ -1518,19 +1526,8 @@
*/
void of_node_put(struct device_node *node)
{
- if (!node)
- return;
-
- WARN_ON(0 == atomic_read(&node->_users));
-
- if (OF_IS_STALE(node)) {
- if (atomic_dec_and_test(&node->_users)) {
- of_node_cleanup(node);
- return;
- }
- }
- else
- atomic_dec(&node->_users);
+ if (node)
+ kref_put(&node->kref, of_node_release);
}
EXPORT_SYMBOL(of_node_put);
@@ -1773,7 +1770,7 @@
np->properties = proplist;
OF_MARK_DYNAMIC(np);
- of_node_get(np);
+ kref_init(&np->kref);
np->parent = derive_parent(path);
if (!np->parent) {
kfree(np);
@@ -1809,8 +1806,9 @@
}
/*
- * Remove an OF device node from the system.
- * Caller should have already "gotten" np.
+ * "Unplug" a node from the device tree. The caller must hold
+ * a reference to the node. The memory associated with the node
+ * is not freed until its refcount goes to zero.
*/
int of_remove_node(struct device_node *np)
{
@@ -1828,7 +1826,6 @@
of_cleanup_node(np);
write_lock(&devtree_lock);
- OF_MARK_STALE(np);
remove_node_proc_entries(np);
if (allnodes == np)
allnodes = np->allnext;
@@ -1853,6 +1850,7 @@
}
write_unlock(&devtree_lock);
of_node_put(parent);
+ of_node_put(np); /* Must decrement the refcount */
return 0;
}
diff -urN linux-2.5/include/asm-ppc64/prom.h test/include/asm-ppc64/prom.h
--- linux-2.5/include/asm-ppc64/prom.h 2005-01-06 13:13:10.000000000 +1100
+++ test/include/asm-ppc64/prom.h 2005-01-22 20:52:35.000000000 +1100
@@ -149,18 +149,15 @@
struct proc_dir_entry *pde; /* this node's proc directory */
struct proc_dir_entry *name_link; /* name symlink */
struct proc_dir_entry *addr_link; /* addr symlink */
- atomic_t _users; /* reference count */
+ struct kref kref;
unsigned long _flags;
};
extern struct device_node *of_chosen;
/* flag descriptions */
-#define OF_STALE 0 /* node is slated for deletion */
#define OF_DYNAMIC 1 /* node and properties were allocated via kmalloc */
-#define OF_IS_STALE(x) test_bit(OF_STALE, &x->_flags)
-#define OF_MARK_STALE(x) set_bit(OF_STALE, &x->_flags)
#define OF_IS_DYNAMIC(x) test_bit(OF_DYNAMIC, &x->_flags)
#define OF_MARK_DYNAMIC(x) set_bit(OF_DYNAMIC, &x->_flags)
-
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