Commit 47c59803 authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Linus Torvalds

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: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: default avatar"Serge E. Hallyn" <serue@us.ibm.com>
Cc: Paul Menage <menage@google.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c012a54a
/*
* 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;
......
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