RCU in kernel/intermodule.c

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Hash: SHA1

This patch, compiled against version 2.6.12-rc1, implements RCU mechanism in intermodule functions.

- --- ./kernel/intermodule.c.orig 2005-04-01 19:25:26.000000000 +0000
+++ ./kernel/intermodule.c 2005-04-02 02:46:22.000000000 +0000
@@ -3,7 +3,7 @@
/* Written by Keith Owens <[email protected]> Oct 2000 */ #include <linux/module.h>
#include <linux/kmod.h>
- -#include <linux/spinlock.h>
+#include <linux/rcupdate.h>
#include <linux/list.h>
#include <linux/slab.h>

@@ -14,7 +14,6 @@
*/

static struct list_head ime_list = LIST_HEAD_INIT(ime_list);
- -static DEFINE_SPINLOCK(ime_lock);
static int kmalloc_failed;

struct inter_module_entry {
@@ -22,8 +21,17 @@ struct inter_module_entry {
const char *im_name;
struct module *owner;
const void *userdata;
+ struct rcu_head rcu;
};

+static void inter_module_free(struct rcu_head *rcu)
+{
+ struct inter_module_entry *ime;
+
+ ime = container_of(rcu, struct inter_module_entry, rcu);
+ kfree(ime);
+}
+
/**
* inter_module_register - register a new set of inter module data.
* @im_name: an arbitrary string to identify the data, must be unique
@@ -36,7 +44,6 @@ struct inter_module_entry {
*/
void inter_module_register(const char *im_name, struct module *owner, const
void *userdata)
{
- - struct list_head *tmp;
struct inter_module_entry *ime, *ime_new;

if (!(ime_new = kmalloc(sizeof(*ime), GFP_KERNEL))) {
@@ -52,19 +59,15 @@ void inter_module_register(const char *i
ime_new->owner = owner;
ime_new->userdata = userdata;

- - spin_lock(&ime_lock);
- - list_for_each(tmp, &ime_list) {
- - ime = list_entry(tmp, struct inter_module_entry, list);
+ list_for_each_entry(ime, &ime_list, list) {
if (strcmp(ime->im_name, im_name) == 0) {
- - spin_unlock(&ime_lock);
kfree(ime_new);
/* Program logic error, fatal */
printk(KERN_ERR "inter_module_register: duplicate im_name '%s'", im_name); BUG();
}
}
- - list_add(&(ime_new->list), &ime_list);
- - spin_unlock(&ime_lock);
+ list_add_rcu(&ime_new->list, &ime_list);
}

/**
@@ -77,20 +80,15 @@ void inter_module_register(const char *i
*/
void inter_module_unregister(const char *im_name) {
- - struct list_head *tmp;
struct inter_module_entry *ime;

- - spin_lock(&ime_lock);
- - list_for_each(tmp, &ime_list) {
- - ime = list_entry(tmp, struct inter_module_entry, list);
+ list_for_each_entry(ime, &ime_list, list) {
if (strcmp(ime->im_name, im_name) == 0) {
- - list_del(&(ime->list));
- - spin_unlock(&ime_lock);
- - kfree(ime);
+ list_del_rcu(&(ime->list));
+ call_rcu(&ime->rcu, inter_module_free);
return;
}
}
- - spin_unlock(&ime_lock);
if (kmalloc_failed) {
printk(KERN_ERR
"inter_module_unregister: no entry for '%s', "
@@ -115,20 +113,18 @@ void inter_module_unregister(const char
*/
static const void *inter_module_get(const char *im_name)
{
- - struct list_head *tmp;
struct inter_module_entry *ime;
const void *result = NULL;

- - spin_lock(&ime_lock);
- - list_for_each(tmp, &ime_list) {
- - ime = list_entry(tmp, struct inter_module_entry, list);
+ rcu_read_lock();
+ list_for_each_entry_rcu(ime, &ime_list, list) {
if (strcmp(ime->im_name, im_name) == 0) {
if (try_module_get(ime->owner))
result = ime->userdata;
break;
}
}
- - spin_unlock(&ime_lock);
+ rcu_read_unlock();
return(result);
}

@@ -158,20 +154,18 @@ const void *inter_module_get_request(con
*/
void inter_module_put(const char *im_name)
{
- - struct list_head *tmp;
struct inter_module_entry *ime;

- - spin_lock(&ime_lock);
- - list_for_each(tmp, &ime_list) {
- - ime = list_entry(tmp, struct inter_module_entry, list);
+ rcu_read_lock();
+ list_for_each_entry(ime, &ime_list, list) {
if (strcmp(ime->im_name, im_name) == 0) {
if (ime->owner)
module_put(ime->owner);
- - spin_unlock(&ime_lock);
+ rcu_read_unlock();
return;
}
}
- - spin_unlock(&ime_lock);
+ rcu_read_unlock();
printk(KERN_ERR "inter_module_put: no entry for '%s'", im_name); BUG();
}

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There's no point as these functions are going to go away soon.

Actually 'just' mtd now iirc. agpgart was the penultimate user which got fixed a few months back.

Dave