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authorLai Jiangshan <laijs@cn.fujitsu.com>2008-10-18 20:28:07 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-10-20 08:52:38 -0700
commit47c59803becb55b72b26cdab3838d621a15badc8 (patch)
tree63711f3e41f46288e2fa18db0b4ed734e9b1f668 /security
parentc012a54ae0b2ee2c73499f54596e0f5257288fec (diff)
downloadlinux-linaro-stable-47c59803becb55b72b26cdab3838d621a15badc8.tar.gz
devcgroup: remove spin_lock()
Since we introduced rcu for read side, spin_lock is used only for update. But we always hold cgroup_lock() when update, so spin_lock() is not need. Additional cleanup: 1) include linux/rcupdate.h explicitly 2) remove unused variable cur_devcgroup in devcgroup_update_access() Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Acked-by: "Serge E. Hallyn" <serue@us.ibm.com> Cc: Paul Menage <menage@google.com> Cc: James Morris <jmorris@namei.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'security')
-rw-r--r--security/device_cgroup.c34
1 files changed, 5 insertions, 29 deletions
diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index d5c15a7c67c3..5ba78701adc3 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -1,5 +1,5 @@
/*
- * dev_cgroup.c - device cgroup subsystem
+ * device_cgroup.c - device cgroup subsystem
*
* Copyright 2007 IBM Corp
*/
@@ -10,6 +10,7 @@
#include <linux/list.h>
#include <linux/uaccess.h>
#include <linux/seq_file.h>
+#include <linux/rcupdate.h>
#define ACC_MKNOD 1
#define ACC_READ 2
@@ -22,18 +23,8 @@
/*
* whitelist locking rules:
- * cgroup_lock() cannot be taken under dev_cgroup->lock.
- * dev_cgroup->lock can be taken with or without cgroup_lock().
- *
- * modifications always require cgroup_lock
- * modifications to a list which is visible require the
- * dev_cgroup->lock *and* cgroup_lock()
- * walking the list requires dev_cgroup->lock or cgroup_lock().
- *
- * reasoning: dev_whitelist_copy() needs to kmalloc, so needs
- * a mutex, which the cgroup_lock() is. Since modifying
- * a visible list requires both locks, either lock can be
- * taken for walking the list.
+ * hold cgroup_lock() for update/read.
+ * hold rcu_read_lock() for read.
*/
struct dev_whitelist_item {
@@ -47,7 +38,6 @@ struct dev_whitelist_item {
struct dev_cgroup {
struct cgroup_subsys_state css;
struct list_head whitelist;
- spinlock_t lock;
};
static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
@@ -103,7 +93,6 @@ free_and_exit:
/* Stupid prototype - don't bother combining existing entries */
/*
* called under cgroup_lock()
- * since the list is visible to other tasks, we need the spinlock also
*/
static int dev_whitelist_add(struct dev_cgroup *dev_cgroup,
struct dev_whitelist_item *wh)
@@ -114,7 +103,6 @@ static int dev_whitelist_add(struct dev_cgroup *dev_cgroup,
if (!whcopy)
return -ENOMEM;
- spin_lock(&dev_cgroup->lock);
list_for_each_entry(walk, &dev_cgroup->whitelist, list) {
if (walk->type != wh->type)
continue;
@@ -130,7 +118,6 @@ static int dev_whitelist_add(struct dev_cgroup *dev_cgroup,
if (whcopy != NULL)
list_add_tail_rcu(&whcopy->list, &dev_cgroup->whitelist);
- spin_unlock(&dev_cgroup->lock);
return 0;
}
@@ -144,14 +131,12 @@ static void whitelist_item_free(struct rcu_head *rcu)
/*
* called under cgroup_lock()
- * since the list is visible to other tasks, we need the spinlock also
*/
static void dev_whitelist_rm(struct dev_cgroup *dev_cgroup,
struct dev_whitelist_item *wh)
{
struct dev_whitelist_item *walk, *tmp;
- spin_lock(&dev_cgroup->lock);
list_for_each_entry_safe(walk, tmp, &dev_cgroup->whitelist, list) {
if (walk->type == DEV_ALL)
goto remove;
@@ -169,7 +154,6 @@ remove:
call_rcu(&walk->rcu, whitelist_item_free);
}
}
- spin_unlock(&dev_cgroup->lock);
}
/*
@@ -209,7 +193,6 @@ static struct cgroup_subsys_state *devcgroup_create(struct cgroup_subsys *ss,
}
}
- spin_lock_init(&dev_cgroup->lock);
return &dev_cgroup->css;
}
@@ -325,15 +308,11 @@ static int parent_has_perm(struct dev_cgroup *childcg,
{
struct cgroup *pcg = childcg->css.cgroup->parent;
struct dev_cgroup *parent;
- int ret;
if (!pcg)
return 1;
parent = cgroup_to_devcgroup(pcg);
- spin_lock(&parent->lock);
- ret = may_access_whitelist(parent, wh);
- spin_unlock(&parent->lock);
- return ret;
+ return may_access_whitelist(parent, wh);
}
/*
@@ -352,7 +331,6 @@ static int parent_has_perm(struct dev_cgroup *childcg,
static int devcgroup_update_access(struct dev_cgroup *devcgroup,
int filetype, const char *buffer)
{
- struct dev_cgroup *cur_devcgroup;
const char *b;
char *endp;
int count;
@@ -361,8 +339,6 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
- cur_devcgroup = task_devcgroup(current);
-
memset(&wh, 0, sizeof(wh));
b = buffer;