cgroup: introduce coalesce css_get() and css_put()

[linux-2.6.git] / include / linux / cgroup.h

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 88e8634607266865d965c862296441a95789aad8..14160b5b693f8d2380413b122a8bb32eaf407bd1 100644 (file)
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -28,6 +28,7 @@ struct css_id;
 extern int cgroup_init_early(void);
 extern int cgroup_init(void);
 extern void cgroup_lock(void);
+extern int cgroup_lock_is_held(void);
 extern bool cgroup_lock_live_group(struct cgroup *cgrp);
 extern void cgroup_unlock(void);
 extern void cgroup_fork(struct task_struct *p);
@@ -37,7 +38,7 @@ extern void cgroup_exit(struct task_struct *p, int run_callbacks);
 extern int cgroupstats_build(struct cgroupstats *stats,
                                struct dentry *dentry);
 
-extern struct file_operations proc_cgroup_operations;
+extern const struct file_operations proc_cgroup_operations;
 
 /* Define the enumeration of all cgroup subsystems */
 #define SUBSYS(_x) _x ## _subsys_id,
@@ -75,6 +76,12 @@ enum {
        CSS_REMOVED, /* This CSS is dead */
 };
 
+/* Caller must verify that the css is not for root cgroup */
+static inline void __css_get(struct cgroup_subsys_state *css, int count)
+{
+       atomic_add(count, &css->refcnt);
+}
+
 /*
  * Call css_get() to hold a reference on the css; it can be used
  * for a reference obtained via:
@@ -86,7 +93,7 @@ static inline void css_get(struct cgroup_subsys_state *css)
 {
        /* We don't need to reference count the root state */
        if (!test_bit(CSS_ROOT, &css->flags))
-               atomic_inc(&css->refcnt);
+               __css_get(css, 1);
 }
 
 static inline bool css_is_removed(struct cgroup_subsys_state *css)
@@ -117,11 +124,11 @@ static inline bool css_tryget(struct cgroup_subsys_state *css)
  * css_get() or css_tryget()
  */
 
-extern void __css_put(struct cgroup_subsys_state *css);
+extern void __css_put(struct cgroup_subsys_state *css, int count);
 static inline void css_put(struct cgroup_subsys_state *css)
 {
        if (!test_bit(CSS_ROOT, &css->flags))
-               __css_put(css);
+               __css_put(css, 1);
 }
 
 /* bits in struct cgroup flags field */
@@ -260,6 +267,9 @@ struct css_set {
         * during subsystem registration (at boot time).
         */
        struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
+
+       /* For RCU-protected deletion */
+       struct rcu_head rcu_head;
 };
 
 /*
@@ -422,10 +432,13 @@ struct cgroup_subsys {
                                                  struct cgroup *cgrp);
        int (*pre_destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
        void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
-       int (*can_attach)(struct cgroup_subsys *ss,
-                         struct cgroup *cgrp, struct task_struct *tsk);
+       int (*can_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
+                         struct task_struct *tsk, bool threadgroup);
+       void (*cancel_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
+                         struct task_struct *tsk, bool threadgroup);
        void (*attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
-                       struct cgroup *old_cgrp, struct task_struct *tsk);
+                       struct cgroup *old_cgrp, struct task_struct *tsk,
+                       bool threadgroup);
        void (*fork)(struct cgroup_subsys *ss, struct task_struct *task);
        void (*exit)(struct cgroup_subsys *ss, struct task_struct *task);
        int (*populate)(struct cgroup_subsys *ss,
@@ -482,7 +495,9 @@ 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_check(task->cgroups->subsys[subsys_id],
+                                    rcu_read_lock_held() ||
+                                    cgroup_lock_is_held());
 }
 
 static inline struct cgroup* task_cgroup(struct task_struct *task,