[PATCH 03/10] cgroups: __rcu annotations

From: Arnd Bergmann
Date: Wed Feb 24 2010 - 15:06:09 EST

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Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
include/linux/cgroup.h | 6 ++--
include/linux/sched.h | 2 +-
kernel/cgroup.c | 63 +++++++++++++++++++++++++----------------------
kernel/cpuset.c | 2 +-
4 files changed, 38 insertions(+), 35 deletions(-)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 0008dee..832092d 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -66,7 +66,7 @@ struct cgroup_subsys_state {

unsigned long flags;
/* ID for this css, if possible */
- struct css_id *id;
+ struct css_id __rcu *id;
};

/* bits in struct cgroup_subsys_state flags field */
@@ -190,7 +190,7 @@ struct cgroup {
struct list_head children; /* my children */

struct cgroup *parent; /* my parent */
- struct dentry *dentry; /* cgroup fs entry, RCU protected */
+ struct dentry __rcu *dentry; /* cgroup fs entry, RCU protected */

/* Private pointers for each registered subsystem */
struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
@@ -486,7 +486,7 @@ static inline struct cgroup_subsys_state *cgroup_subsys_state(
static inline struct cgroup_subsys_state *task_subsys_state(
struct task_struct *task, int subsys_id)
{
- return rcu_dereference(task->cgroups->subsys[subsys_id]);
+ return rcu_dereference(task->cgroups)->subsys[subsys_id];
}

static inline struct cgroup* task_cgroup(struct task_struct *task,
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 78efe7c..038e16f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1489,7 +1489,7 @@ struct task_struct {
#endif
#ifdef CONFIG_CGROUPS
/* Control Group info protected by css_set_lock */
- struct css_set *cgroups;
+ struct css_set __rcu *cgroups;
/* cg_list protected by css_set_lock and tsk->alloc_lock */
struct list_head cg_list;
#endif
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index aa3bee5..e0f379e 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -127,7 +127,7 @@ struct css_id {
* is called after synchronize_rcu(). But for safe use, css_is_removed()
* css_tryget() should be used for avoiding race.
*/
- struct cgroup_subsys_state *css;
+ struct cgroup_subsys_state __rcu *css;
/*
* ID of this css.
*/
@@ -605,7 +605,7 @@ static struct cgroup *task_cgroup_from_root(struct task_struct *task,
* task can't change groups, so the only thing that can happen
* is that it exits and its css is set back to init_css_set.
*/
- css = task->cgroups;
+ css = __rcu_dereference(task->cgroups);
if (css == &init_css_set) {
res = &root->top_cgroup;
} else {
@@ -850,7 +850,7 @@ static void cgroup_d_remove_dir(struct dentry *dentry)
*
* CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
*/
-DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
+static DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);

static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
{
@@ -1081,9 +1081,11 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
struct cgroupfs_root *root = sb->s_fs_info;
struct cgroup *cgrp = &root->top_cgroup;
struct cgroup_sb_opts opts;
+ struct dentry *dentry;

lock_kernel();
- mutex_lock(&cgrp->dentry->d_inode->i_mutex);
+ dentry = __rcu_dereference(cgrp->dentry);
+ mutex_lock(&dentry->d_inode->i_mutex);
mutex_lock(&cgroup_mutex);

/* See what subsystems are wanted */
@@ -1116,7 +1118,7 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
kfree(opts.release_agent);
kfree(opts.name);
mutex_unlock(&cgroup_mutex);
- mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
+ mutex_unlock(&dentry->d_inode->i_mutex);
unlock_kernel();
return ret;
}
@@ -1375,7 +1377,7 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
root_count++;

sb->s_root->d_fsdata = root_cgrp;
- root->top_cgroup.dentry = sb->s_root;
+ __rcu_assign_pointer(root->top_cgroup.dentry, sb->s_root);

/* Link the top cgroup in this hierarchy into all
* the css_set objects */
@@ -1513,7 +1515,7 @@ int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
int len = dentry->d_name.len;
if ((start -= len) < buf)
return -ENAMETOOLONG;
- memcpy(start, cgrp->dentry->d_name.name, len);
+ memcpy(start, dentry->d_name.name, len);
cgrp = cgrp->parent;
if (!cgrp)
break;
@@ -1559,7 +1561,7 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
}

task_lock(tsk);
- cg = tsk->cgroups;
+ cg = __rcu_dereference(tsk->cgroups);
get_css_set(cg);
task_unlock(tsk);
/*
@@ -1986,7 +1988,7 @@ static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
struct dentry *parent;
int error = 0;

- parent = cgrp->parent->dentry;
+ parent = __rcu_dereference(cgrp->parent->dentry);
error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
if (!error) {
dentry->d_fsdata = cgrp;
@@ -2030,7 +2032,7 @@ int cgroup_add_file(struct cgroup *cgrp,
struct cgroup_subsys *subsys,
const struct cftype *cft)
{
- struct dentry *dir = cgrp->dentry;
+ struct dentry *dir = __rcu_dereference(cgrp->dentry);
struct dentry *dentry;
int error;
mode_t mode;
@@ -2135,7 +2137,7 @@ static void cgroup_enable_task_cg_lists(void)
* entry won't be deleted though the process has exited.
*/
if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
- list_add(&p->cg_list, &p->cgroups->tasks);
+ list_add(&p->cg_list, &__rcu_dereference(p->cgroups)->tasks);
task_unlock(p);
} while_each_thread(g, p);
write_unlock(&css_set_lock);
@@ -2828,7 +2830,7 @@ static int cgroup_populate_dir(struct cgroup *cgrp)
struct cgroup_subsys *ss;

/* First clear out any existing files */
- cgroup_clear_directory(cgrp->dentry);
+ cgroup_clear_directory(__rcu_dereference(cgrp->dentry));

err = cgroup_add_files(cgrp, NULL, files, ARRAY_SIZE(files));
if (err < 0)
@@ -2852,7 +2854,7 @@ static int cgroup_populate_dir(struct cgroup *cgrp)
* from RCU-read-side without locks.
*/
if (css->id)
- rcu_assign_pointer(css->id->css, css);
+ rcu_assign_pointer(__rcu_dereference(css->id)->css, css);
}

return 0;
@@ -2960,13 +2962,13 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
goto err_remove;

/* The cgroup directory was pre-locked for us */
- BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
+ BUG_ON(!mutex_is_locked(&__rcu_dereference(cgrp->dentry)->d_inode->i_mutex));

err = cgroup_populate_dir(cgrp);
/* If err < 0, we have a half-filled directory - oh well ;) */

mutex_unlock(&cgroup_mutex);
- mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
+ mutex_unlock(&__rcu_dereference(cgrp->dentry)->d_inode->i_mutex);

return 0;

@@ -3164,8 +3166,8 @@ again:
list_del(&cgrp->sibling);
cgroup_unlock_hierarchy(cgrp->root);

- spin_lock(&cgrp->dentry->d_lock);
- d = dget(cgrp->dentry);
+ spin_lock(&__rcu_dereference(cgrp->dentry)->d_lock);
+ d = dget(__rcu_dereference(cgrp->dentry));
spin_unlock(&d->d_lock);

cgroup_d_remove_dir(d);
@@ -3203,7 +3205,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
/* At system boot, before all subsystems have been
* registered, no tasks have been forked, so we don't
* need to invoke fork callbacks here. */
- BUG_ON(!list_empty(&init_task.tasks));
+ BUG_ON(!list_empty_rcu(&init_task.tasks));

mutex_init(&ss->hierarchy_mutex);
lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
@@ -3226,7 +3228,7 @@ int __init cgroup_init_early(void)
css_set_count = 1;
init_cgroup_root(&rootnode);
root_count = 1;
- init_task.cgroups = &init_css_set;
+ __rcu_assign_pointer(init_task.cgroups, &init_css_set);

init_css_set_link.cg = &init_css_set;
init_css_set_link.cgrp = dummytop;
@@ -3425,7 +3427,7 @@ void cgroup_fork(struct task_struct *child)
{
task_lock(current);
child->cgroups = current->cgroups;
- get_css_set(child->cgroups);
+ get_css_set(__rcu_dereference(child->cgroups));
task_unlock(current);
INIT_LIST_HEAD(&child->cg_list);
}
@@ -3465,7 +3467,8 @@ void cgroup_post_fork(struct task_struct *child)
write_lock(&css_set_lock);
task_lock(child);
if (list_empty(&child->cg_list))
- list_add(&child->cg_list, &child->cgroups->tasks);
+ list_add(&child->cg_list,
+ &__rcu_dereference(child->cgroups)->tasks);
task_unlock(child);
write_unlock(&css_set_lock);
}
@@ -3532,8 +3535,8 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)

/* Reassign the task to the init_css_set. */
task_lock(tsk);
- cg = tsk->cgroups;
- tsk->cgroups = &init_css_set;
+ cg = __rcu_dereference(tsk->cgroups);
+ __rcu_assign_pointer(tsk->cgroups, &init_css_set);
task_unlock(tsk);
if (cg)
put_css_set_taskexit(cg);
@@ -3583,19 +3586,19 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
/* Keep the cgroup alive */
task_lock(tsk);
parent = task_cgroup(tsk, subsys->subsys_id);
- cg = tsk->cgroups;
+ cg = __rcu_dereference(tsk->cgroups);
get_css_set(cg);
task_unlock(tsk);

mutex_unlock(&cgroup_mutex);

/* Now do the VFS work to create a cgroup */
- inode = parent->dentry->d_inode;
+ inode = __rcu_dereference(parent->dentry)->d_inode;

/* Hold the parent directory mutex across this operation to
* stop anyone else deleting the new cgroup */
mutex_lock(&inode->i_mutex);
- dentry = lookup_one_len(nodename, parent->dentry, strlen(nodename));
+ dentry = lookup_one_len(nodename, __rcu_dereference(parent->dentry), strlen(nodename));
if (IS_ERR(dentry)) {
printk(KERN_INFO
"cgroup: Couldn't allocate dentry for %s: %ld\n", nodename,
@@ -3864,7 +3867,7 @@ static void __free_css_id_cb(struct rcu_head *head)

void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)
{
- struct css_id *id = css->id;
+ struct css_id *id = __rcu_dereference(css->id);
/* When this is called before css_id initialization, id can be NULL */
if (!id)
return;
@@ -3941,8 +3944,8 @@ static int __init cgroup_subsys_init_idr(struct cgroup_subsys *ss)
return PTR_ERR(newid);

newid->stack[0] = newid->id;
- newid->css = rootcss;
- rootcss->id = newid;
+ __rcu_assign_pointer(newid->css, rootcss);
+ __rcu_assign_pointer(rootcss->id, newid);
return 0;
}

@@ -3957,7 +3960,7 @@ static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
parent_css = parent->subsys[subsys_id];
child_css = child->subsys[subsys_id];
depth = css_depth(parent_css) + 1;
- parent_id = parent_css->id;
+ parent_id = __rcu_dereference(parent_css->id);

child_id = get_new_cssid(ss, depth);
if (IS_ERR(child_id))
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index ba401fa..42d4851 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2434,7 +2434,7 @@ void cpuset_print_task_mems_allowed(struct task_struct *tsk)
{
struct dentry *dentry;

- dentry = task_cs(tsk)->css.cgroup->dentry;
+ dentry = __rcu_dereference(task_cs(tsk)->css.cgroup->dentry);
spin_lock(&cpuset_buffer_lock);
snprintf(cpuset_name, CPUSET_NAME_LEN,
dentry ? (const char *)dentry->d_name.name : "/");
--
1.6.3.3

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