#ifndef _LINUX_CGROUP_H
  #define _LINUX_CGROUP_H
  /*
   *  cgroup interface
   *
   *  Copyright (C) 2003 BULL SA
   *  Copyright (C) 2004-2006 Silicon Graphics, Inc.
   *
   */
  
  #include <linux/sched.h>

  #include <linux/cpumask.h>
  #include <linux/nodemask.h>
  #include <linux/rcupdate.h>

  #include <linux/cgroupstats.h>

  #include <linux/prio_heap.h>

  #include <linux/rwsem.h>

  #include <linux/idr.h>

  
  #ifdef CONFIG_CGROUPS
  
  struct cgroupfs_root;
  struct cgroup_subsys;
  struct inode;

  struct cgroup;

  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);
  extern void cgroup_fork_callbacks(struct task_struct *p);

  extern void cgroup_post_fork(struct task_struct *p);

  extern void cgroup_exit(struct task_struct *p, int run_callbacks);

  extern int cgroupstats_build(struct cgroupstats *stats,
  				struct dentry *dentry);

  extern int cgroup_load_subsys(struct cgroup_subsys *ss);

  extern void cgroup_unload_subsys(struct cgroup_subsys *ss);

  extern const struct file_operations proc_cgroup_operations;

  /* Define the enumeration of all builtin cgroup subsystems */

  #define SUBSYS(_x) _x ## _subsys_id,
  enum cgroup_subsys_id {
  #include <linux/cgroup_subsys.h>

  	CGROUP_BUILTIN_SUBSYS_COUNT

  };
  #undef SUBSYS

  /*
   * This define indicates the maximum number of subsystems that can be loaded
   * at once. We limit to this many since cgroupfs_root has subsys_bits to keep
   * track of all of them.
   */
  #define CGROUP_SUBSYS_COUNT (BITS_PER_BYTE*sizeof(unsigned long))

  /* Per-subsystem/per-cgroup state maintained by the system. */
  struct cgroup_subsys_state {

  	/*
  	 * The cgroup that this subsystem is attached to. Useful

  	 * for subsystems that want to know about the cgroup

  	 * hierarchy structure
  	 */

  	struct cgroup *cgroup;

  	/*
  	 * State maintained by the cgroup system to allow subsystems

  	 * to be "busy". Should be accessed via css_get(),

  	 * css_tryget() and and css_put().
  	 */

  
  	atomic_t refcnt;
  
  	unsigned long flags;

  	/* ID for this css, if possible */

  	struct css_id __rcu *id;

  };
  
  /* bits in struct cgroup_subsys_state flags field */
  enum {
  	CSS_ROOT, /* This CSS is the root of the subsystem */

  	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:
   * - an existing ref-counted reference to the css
   * - task->cgroups for a locked task

   */
  
  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))

  		__css_get(css, 1);

  }

  
  static inline bool css_is_removed(struct cgroup_subsys_state *css)
  {
  	return test_bit(CSS_REMOVED, &css->flags);
  }
  
  /*
   * Call css_tryget() to take a reference on a css if your existing
   * (known-valid) reference isn't already ref-counted. Returns false if
   * the css has been destroyed.
   */
  
  static inline bool css_tryget(struct cgroup_subsys_state *css)
  {
  	if (test_bit(CSS_ROOT, &css->flags))
  		return true;
  	while (!atomic_inc_not_zero(&css->refcnt)) {
  		if (test_bit(CSS_REMOVED, &css->flags))
  			return false;

  		cpu_relax();

  	}
  	return true;
  }

  /*
   * css_put() should be called to release a reference taken by

   * css_get() or css_tryget()

   */

  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, 1);

  }

  /* bits in struct cgroup flags field */
  enum {
  	/* Control Group is dead */
  	CGRP_REMOVED,

  	/*
  	 * Control Group has previously had a child cgroup or a task,
  	 * but no longer (only if CGRP_NOTIFY_ON_RELEASE is set)
  	 */

  	CGRP_RELEASABLE,
  	/* Control Group requires release notifications to userspace */
  	CGRP_NOTIFY_ON_RELEASE,

  	/*
  	 * A thread in rmdir() is wating for this cgroup.
  	 */
  	CGRP_WAIT_ON_RMDIR,

  	/*
  	 * Clone cgroup values when creating a new child cgroup
  	 */
  	CGRP_CLONE_CHILDREN,

  };

  /* which pidlist file are we talking about? */
  enum cgroup_filetype {
  	CGROUP_FILE_PROCS,
  	CGROUP_FILE_TASKS,
  };
  
  /*
   * A pidlist is a list of pids that virtually represents the contents of one
   * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
   * a pair (one each for procs, tasks) for each pid namespace that's relevant
   * to the cgroup.
   */

  struct cgroup_pidlist {

  	/*
  	 * used to find which pidlist is wanted. doesn't change as long as
  	 * this particular list stays in the list.
  	 */
  	struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;

  	/* array of xids */
  	pid_t *list;
  	/* how many elements the above list has */
  	int length;
  	/* how many files are using the current array */
  	int use_count;

  	/* each of these stored in a list by its cgroup */
  	struct list_head links;
  	/* pointer to the cgroup we belong to, for list removal purposes */
  	struct cgroup *owner;
  	/* protects the other fields */
  	struct rw_semaphore mutex;

  };

  struct cgroup {
  	unsigned long flags;		/* "unsigned long" so bitops work */

  	/*
  	 * count users of this cgroup. >0 means busy, but doesn't
  	 * necessarily indicate the number of tasks in the cgroup
  	 */

  	atomic_t count;
  
  	/*
  	 * We link our 'sibling' struct into our parent's 'children'.
  	 * Our children link their 'sibling' into our 'children'.
  	 */
  	struct list_head sibling;	/* my parent's children */
  	struct list_head children;	/* my children */

  	struct cgroup *parent;		/* my parent */

  	struct dentry __rcu *dentry;	/* cgroup fs entry, RCU protected */

  
  	/* Private pointers for each registered subsystem */
  	struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
  
  	struct cgroupfs_root *root;
  	struct cgroup *top_cgroup;

  
  	/*
  	 * List of cg_cgroup_links pointing at css_sets with
  	 * tasks in this cgroup. Protected by css_set_lock
  	 */
  	struct list_head css_sets;

  
  	/*
  	 * Linked list running through all cgroups that can
  	 * potentially be reaped by the release agent. Protected by
  	 * release_list_lock
  	 */
  	struct list_head release_list;

  	/*
  	 * list of pidlists, up to two for each namespace (one for procs, one
  	 * for tasks); created on demand.
  	 */
  	struct list_head pidlists;
  	struct mutex pidlist_mutex;

  
  	/* For RCU-protected deletion */
  	struct rcu_head rcu_head;

  	/* List of events which userspace want to receive */

  	struct list_head event_list;
  	spinlock_t event_list_lock;

  };

  /*
   * A css_set is a structure holding pointers to a set of

   * cgroup_subsys_state objects. This saves space in the task struct
   * object and speeds up fork()/exit(), since a single inc/dec and a

   * list_add()/del() can bump the reference count on the entire cgroup
   * set for a task.

   */
  
  struct css_set {
  
  	/* Reference count */

  	atomic_t refcount;

  
  	/*

  	 * List running through all cgroup groups in the same hash
  	 * slot. Protected by css_set_lock
  	 */
  	struct hlist_node hlist;
  
  	/*

  	 * List running through all tasks using this cgroup
  	 * group. Protected by css_set_lock
  	 */
  	struct list_head tasks;
  
  	/*
  	 * List of cg_cgroup_link objects on link chains from
  	 * cgroups referenced from this css_set. Protected by
  	 * css_set_lock
  	 */
  	struct list_head cg_links;
  
  	/*
  	 * Set of subsystem states, one for each subsystem. This array
  	 * is immutable after creation apart from the init_css_set

  	 * during subsystem registration (at boot time) and modular subsystem
  	 * loading/unloading.

  	 */
  	struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];

  
  	/* For RCU-protected deletion */
  	struct rcu_head rcu_head;

  };

  /*
   * cgroup_map_cb is an abstract callback API for reporting map-valued
   * control files
   */
  
  struct cgroup_map_cb {
  	int (*fill)(struct cgroup_map_cb *cb, const char *key, u64 value);
  	void *state;
  };

  /*
   * struct cftype: handler definitions for cgroup control files

   *
   * When reading/writing to a file:

   *	- the cgroup to use is file->f_dentry->d_parent->d_fsdata

   *	- the 'cftype' of the file is file->f_dentry->d_fsdata
   */
  
  #define MAX_CFTYPE_NAME 64
  struct cftype {

  	/*
  	 * By convention, the name should begin with the name of the
  	 * subsystem, followed by a period
  	 */

  	char name[MAX_CFTYPE_NAME];
  	int private;

  	/*
  	 * If not 0, file mode is set to this value, otherwise it will
  	 * be figured out automatically
  	 */
  	mode_t mode;

  
  	/*
  	 * If non-zero, defines the maximum length of string that can
  	 * be passed to write_string; defaults to 64
  	 */
  	size_t max_write_len;

  	int (*open)(struct inode *inode, struct file *file);
  	ssize_t (*read)(struct cgroup *cgrp, struct cftype *cft,
  			struct file *file,
  			char __user *buf, size_t nbytes, loff_t *ppos);

  	/*

  	 * read_u64() is a shortcut for the common case of returning a

  	 * single integer. Use it in place of read()
  	 */

  	u64 (*read_u64)(struct cgroup *cgrp, struct cftype *cft);

  	/*

  	 * read_s64() is a signed version of read_u64()
  	 */

  	s64 (*read_s64)(struct cgroup *cgrp, struct cftype *cft);

  	/*

  	 * read_map() is used for defining a map of key/value
  	 * pairs. It should call cb->fill(cb, key, value) for each
  	 * entry. The key/value pairs (and their ordering) should not
  	 * change between reboots.
  	 */

  	int (*read_map)(struct cgroup *cont, struct cftype *cft,
  			struct cgroup_map_cb *cb);

  	/*
  	 * read_seq_string() is used for outputting a simple sequence
  	 * using seqfile.
  	 */

  	int (*read_seq_string)(struct cgroup *cont, struct cftype *cft,
  			       struct seq_file *m);

  	ssize_t (*write)(struct cgroup *cgrp, struct cftype *cft,
  			 struct file *file,
  			 const char __user *buf, size_t nbytes, loff_t *ppos);

  
  	/*

  	 * write_u64() is a shortcut for the common case of accepting

  	 * a single integer (as parsed by simple_strtoull) from
  	 * userspace. Use in place of write(); return 0 or error.
  	 */

  	int (*write_u64)(struct cgroup *cgrp, struct cftype *cft, u64 val);

  	/*
  	 * write_s64() is a signed version of write_u64()
  	 */

  	int (*write_s64)(struct cgroup *cgrp, struct cftype *cft, s64 val);

  	/*

  	 * write_string() is passed a nul-terminated kernelspace
  	 * buffer of maximum length determined by max_write_len.
  	 * Returns 0 or -ve error code.
  	 */
  	int (*write_string)(struct cgroup *cgrp, struct cftype *cft,
  			    const char *buffer);
  	/*

  	 * trigger() callback can be used to get some kick from the
  	 * userspace, when the actual string written is not important
  	 * at all. The private field can be used to determine the
  	 * kick type for multiplexing.
  	 */
  	int (*trigger)(struct cgroup *cgrp, unsigned int event);

  	int (*release)(struct inode *inode, struct file *file);

  
  	/*
  	 * register_event() callback will be used to add new userspace
  	 * waiter for changes related to the cftype. Implement it if
  	 * you want to provide this functionality. Use eventfd_signal()
  	 * on eventfd to send notification to userspace.
  	 */
  	int (*register_event)(struct cgroup *cgrp, struct cftype *cft,
  			struct eventfd_ctx *eventfd, const char *args);
  	/*
  	 * unregister_event() callback will be called when userspace
  	 * closes the eventfd or on cgroup removing.
  	 * This callback must be implemented, if you want provide
  	 * notification functionality.

  	 */

  	void (*unregister_event)(struct cgroup *cgrp, struct cftype *cft,

  			struct eventfd_ctx *eventfd);

  };

  struct cgroup_scanner {
  	struct cgroup *cg;
  	int (*test_task)(struct task_struct *p, struct cgroup_scanner *scan);
  	void (*process_task)(struct task_struct *p,
  			struct cgroup_scanner *scan);
  	struct ptr_heap *heap;

  	void *data;

  };

  /*
   * Add a new file to the given cgroup directory. Should only be
   * called by subsystems from within a populate() method
   */

  int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,

  		       const struct cftype *cft);

  /*
   * Add a set of new files to the given cgroup directory. Should
   * only be called by subsystems from within a populate() method
   */

  int cgroup_add_files(struct cgroup *cgrp,

  			struct cgroup_subsys *subsys,
  			const struct cftype cft[],
  			int count);

  int cgroup_is_removed(const struct cgroup *cgrp);

  int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);

  int cgroup_task_count(const struct cgroup *cgrp);

  /* Return true if cgrp is a descendant of the task's cgroup */
  int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task);

  /*

   * When the subsys has to access css and may add permanent refcnt to css,
   * it should take care of racy conditions with rmdir(). Following set of
   * functions, is for stop/restart rmdir if necessary.
   * Because these will call css_get/put, "css" should be alive css.
   *
   *  cgroup_exclude_rmdir();
   *  ...do some jobs which may access arbitrary empty cgroup
   *  cgroup_release_and_wakeup_rmdir();
   *
   *  When someone removes a cgroup while cgroup_exclude_rmdir() holds it,
   *  it sleeps and cgroup_release_and_wakeup_rmdir() will wake him up.
   */
  
  void cgroup_exclude_rmdir(struct cgroup_subsys_state *css);
  void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css);
  
  /*

   * Control Group subsystem type.
   * See Documentation/cgroups/cgroups.txt for details
   */

  
  struct cgroup_subsys {
  	struct cgroup_subsys_state *(*create)(struct cgroup_subsys *ss,

  						  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_task)(struct cgroup *cgrp, struct task_struct *tsk);

  	void (*cancel_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,

  			      struct task_struct *tsk);
  	void (*pre_attach)(struct cgroup *cgrp);
  	void (*attach_task)(struct cgroup *cgrp, struct task_struct *tsk);

  	void (*attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,

  		       struct cgroup *old_cgrp, struct task_struct *tsk);

  	void (*fork)(struct cgroup_subsys *ss, struct task_struct *task);

  	void (*exit)(struct cgroup_subsys *ss, struct cgroup *cgrp,
  			struct cgroup *old_cgrp, struct task_struct *task);

  	int (*populate)(struct cgroup_subsys *ss,

  			struct cgroup *cgrp);
  	void (*post_clone)(struct cgroup_subsys *ss, struct cgroup *cgrp);

  	void (*bind)(struct cgroup_subsys *ss, struct cgroup *root);

  	int subsys_id;
  	int active;

  	int disabled;

  	int early_init;

  	/*
  	 * True if this subsys uses ID. ID is not available before cgroup_init()
  	 * (not available in early_init time.)
  	 */
  	bool use_id;

  #define MAX_CGROUP_TYPE_NAMELEN 32
  	const char *name;

  	/*
  	 * Protects sibling/children links of cgroups in this
  	 * hierarchy, plus protects which hierarchy (or none) the
  	 * subsystem is a part of (i.e. root/sibling).  To avoid
  	 * potential deadlocks, the following operations should not be
  	 * undertaken while holding any hierarchy_mutex:
  	 *
  	 * - allocating memory
  	 * - initiating hotplug events
  	 */
  	struct mutex hierarchy_mutex;

  	struct lock_class_key subsys_key;

  	/*
  	 * Link to parent, and list entry in parent's children.
  	 * Protected by this->hierarchy_mutex and cgroup_lock()
  	 */
  	struct cgroupfs_root *root;

  	struct list_head sibling;

  	/* used when use_id == true */
  	struct idr idr;

  	rwlock_t id_lock;

  
  	/* should be defined only by modular subsystems */
  	struct module *module;

  };
  
  #define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
  #include <linux/cgroup_subsys.h>
  #undef SUBSYS
  
  static inline struct cgroup_subsys_state *cgroup_subsys_state(

  	struct cgroup *cgrp, int subsys_id)

  {

  	return cgrp->subsys[subsys_id];

  }

  /*
   * function to get the cgroup_subsys_state which allows for extra
   * rcu_dereference_check() conditions, such as locks used during the
   * cgroup_subsys::attach() methods.
   */
  #define task_subsys_state_check(task, subsys_id, __c)			\
  	rcu_dereference_check(task->cgroups->subsys[subsys_id],		\

  			      lockdep_is_held(&task->alloc_lock) ||	\
  			      cgroup_lock_is_held() || (__c))
  
  static inline struct cgroup_subsys_state *
  task_subsys_state(struct task_struct *task, int subsys_id)

  {

  	return task_subsys_state_check(task, subsys_id, false);

  }
  
  static inline struct cgroup* task_cgroup(struct task_struct *task,
  					       int subsys_id)
  {
  	return task_subsys_state(task, subsys_id)->cgroup;
  }

  /* A cgroup_iter should be treated as an opaque object */
  struct cgroup_iter {
  	struct list_head *cg_link;
  	struct list_head *task;
  };

  /*
   * To iterate across the tasks in a cgroup:

   *

   * 1) call cgroup_iter_start to initialize an iterator

   *
   * 2) call cgroup_iter_next() to retrieve member tasks until it
   *    returns NULL or until you want to end the iteration
   *
   * 3) call cgroup_iter_end() to destroy the iterator.

   *

   * Or, call cgroup_scan_tasks() to iterate through every task in a
   * cgroup - cgroup_scan_tasks() holds the css_set_lock when calling
   * the test_task() callback, but not while calling the process_task()
   * callback.

   */

  void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it);
  struct task_struct *cgroup_iter_next(struct cgroup *cgrp,

  					struct cgroup_iter *it);

  void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it);

  int cgroup_scan_tasks(struct cgroup_scanner *scan);

  int cgroup_attach_task(struct cgroup *, struct task_struct *);

  int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
  
  static inline int cgroup_attach_task_current_cg(struct task_struct *tsk)
  {
  	return cgroup_attach_task_all(current, tsk);
  }

  /*
   * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
   * if cgroup_subsys.use_id == true. It can be used for looking up and scanning.
   * CSS ID is assigned at cgroup allocation (create) automatically
   * and removed when subsys calls free_css_id() function. This is because
   * the lifetime of cgroup_subsys_state is subsys's matter.
   *
   * Looking up and scanning function should be called under rcu_read_lock().
   * Taking cgroup_mutex()/hierarchy_mutex() is not necessary for following calls.
   * But the css returned by this routine can be "not populated yet" or "being
   * destroyed". The caller should check css and cgroup's status.
   */
  
  /*
   * Typically Called at ->destroy(), or somewhere the subsys frees
   * cgroup_subsys_state.
   */
  void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css);
  
  /* Find a cgroup_subsys_state which has given ID */
  
  struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id);
  
  /*
   * Get a cgroup whose id is greater than or equal to id under tree of root.
   * Returning a cgroup_subsys_state or NULL.
   */
  struct cgroup_subsys_state *css_get_next(struct cgroup_subsys *ss, int id,
  		struct cgroup_subsys_state *root, int *foundid);
  
  /* Returns true if root is ancestor of cg */
  bool css_is_ancestor(struct cgroup_subsys_state *cg,

  		     const struct cgroup_subsys_state *root);

  
  /* Get id and depth of css */
  unsigned short css_id(struct cgroup_subsys_state *css);
  unsigned short css_depth(struct cgroup_subsys_state *css);

  struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id);

  #else /* !CONFIG_CGROUPS */
  
  static inline int cgroup_init_early(void) { return 0; }
  static inline int cgroup_init(void) { return 0; }

  static inline void cgroup_fork(struct task_struct *p) {}
  static inline void cgroup_fork_callbacks(struct task_struct *p) {}

  static inline void cgroup_post_fork(struct task_struct *p) {}

  static inline void cgroup_exit(struct task_struct *p, int callbacks) {}

  
  static inline void cgroup_lock(void) {}
  static inline void cgroup_unlock(void) {}

  static inline int cgroupstats_build(struct cgroupstats *stats,
  					struct dentry *dentry)
  {
  	return -EINVAL;
  }

  /* No cgroups - nothing to do */

  static inline int cgroup_attach_task_all(struct task_struct *from,
  					 struct task_struct *t)
  {
  	return 0;
  }

  static inline int cgroup_attach_task_current_cg(struct task_struct *t)
  {
  	return 0;
  }

  #endif /* !CONFIG_CGROUPS */
  
  #endif /* _LINUX_CGROUP_H */