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    Subject[PATCH 03/10] cgroups: __rcu annotations
    Date
    Signed-off-by: Arnd Bergmann <arnd@arndb.de>
    ---
    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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