#include <linux/workqueue.h>
#include <linux/xattr.h>
#include <linux/fs.h>
+#include <linux/percpu-refcount.h>
#ifdef CONFIG_CGROUPS
*/
struct cgroup *cgroup;
- /*
- * State maintained by the cgroup system to allow subsystems
- * to be "busy". Should be accessed via css_get(),
- * css_tryget() and css_put().
- */
-
- atomic_t refcnt;
+ /* reference count - access via css_[try]get() and css_put() */
+ struct percpu_ref refcnt;
unsigned long flags;
/* ID for this css, if possible */
CSS_ONLINE = (1 << 1), /* between ->css_online() and ->css_offline() */
};
-/* 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
+/**
+ * css_get - obtain a reference on the specified css
+ * @css: target css
+ *
+ * The caller must already have a reference.
*/
-
static inline void css_get(struct cgroup_subsys_state *css)
{
/* We don't need to reference count the root state */
if (!(css->flags & CSS_ROOT))
- __css_get(css, 1);
+ percpu_ref_get(&css->refcnt);
}
-/*
- * 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.
+/**
+ * css_tryget - try to obtain a reference on the specified css
+ * @css: target css
+ *
+ * Obtain a reference on @css if it's alive. The caller naturally needs to
+ * ensure that @css is accessible but doesn't have to be holding a
+ * reference on it - IOW, RCU protected access is good enough for this
+ * function. Returns %true if a reference count was successfully obtained;
+ * %false otherwise.
*/
-
-extern bool __css_tryget(struct cgroup_subsys_state *css);
static inline bool css_tryget(struct cgroup_subsys_state *css)
{
if (css->flags & CSS_ROOT)
return true;
- return __css_tryget(css);
+ return percpu_ref_tryget(&css->refcnt);
}
-/*
- * css_put() should be called to release a reference taken by
- * css_get() or css_tryget()
+/**
+ * css_put - put a css reference
+ * @css: target css
+ *
+ * Put a reference obtained via css_get() and css_tryget().
*/
-
-extern void __css_put(struct cgroup_subsys_state *css);
static inline void css_put(struct cgroup_subsys_state *css)
{
if (!(css->flags & CSS_ROOT))
- __css_put(css);
+ percpu_ref_put(&css->refcnt);
}
/* bits in struct cgroup flags field */
enum {
/* Control Group is dead */
- CGRP_REMOVED,
+ CGRP_DEAD,
/*
* Control Group has previously had a child cgroup or a task,
* but no longer (only if CGRP_NOTIFY_ON_RELEASE is set)
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;
-
int id; /* ida allocated in-hierarchy ID */
/*
struct cgroup *parent; /* my parent */
struct dentry *dentry; /* cgroup fs entry, RCU protected */
+ /*
+ * Monotonically increasing unique serial number which defines a
+ * uniform order among all cgroups. It's guaranteed that all
+ * ->children lists are in the ascending order of ->serial_nr.
+ * It's used to allow interrupting and resuming iterations.
+ */
+ u64 serial_nr;
+
/*
* This is a copy of dentry->d_name, and it's needed because
* we can't use dentry->d_name in cgroup_path().
struct cgroupfs_root *root;
/*
- * List of cg_cgroup_links pointing at css_sets with
- * tasks in this cgroup. Protected by css_set_lock
+ * List of cgrp_cset_links pointing at css_sets with tasks in this
+ * cgroup. Protected by css_set_lock.
*/
- struct list_head css_sets;
-
- struct list_head allcg_node; /* cgroupfs_root->allcg_list */
- struct list_head cft_q_node; /* used during cftype add/rm */
+ struct list_head cset_links;
/*
* Linked list running through all cgroups that can
struct list_head pidlists;
struct mutex pidlist_mutex;
- /* For RCU-protected deletion */
+ /* For css percpu_ref killing and RCU-protected deletion */
struct rcu_head rcu_head;
- struct work_struct free_work;
+ struct work_struct destroy_work;
+ atomic_t css_kill_cnt;
/* List of events which userspace want to receive */
struct list_head event_list;
*
* - Remount is disallowed.
*
+ * - rename(2) is disallowed.
+ *
+ * - "tasks" is removed. Everything should be at process
+ * granularity. Use "cgroup.procs" instead.
+ *
+ * - "release_agent" and "notify_on_release" are removed.
+ * Replacement notification mechanism will be implemented.
+ *
+ * - cpuset: tasks will be kept in empty cpusets when hotplug happens
+ * and take masks of ancestors with non-empty cpus/mems, instead of
+ * being moved to an ancestor.
+ *
+ * - cpuset: a task can be moved into an empty cpuset, and again it
+ * takes masks of ancestors.
+ *
* - memcg: use_hierarchy is on by default and the cgroup file for
* the flag is not created.
*
* - blkcg: blk-throttle becomes properly hierarchical.
- *
- * The followings are planned changes.
- *
- * - release_agent will be disallowed once replacement notification
- * mechanism is implemented.
*/
CGRP_ROOT_SANE_BEHAVIOR = (1 << 0),
CGRP_ROOT_NOPREFIX = (1 << 1), /* mounted subsystems have no named prefix */
CGRP_ROOT_XATTR = (1 << 2), /* supports extended attributes */
+
+ /* mount options live below bit 16 */
+ CGRP_ROOT_OPTION_MASK = (1 << 16) - 1,
+
+ CGRP_ROOT_SUBSYS_BOUND = (1 << 16), /* subsystems finished binding */
};
/*
struct cgroupfs_root {
struct super_block *sb;
- /*
- * The bitmask of subsystems intended to be attached to this
- * hierarchy
- */
+ /* The bitmask of subsystems attached to this hierarchy */
unsigned long subsys_mask;
/* Unique id for this hierarchy. */
int hierarchy_id;
- /* The bitmask of subsystems currently attached to this hierarchy */
- unsigned long actual_subsys_mask;
-
/* A list running through the attached subsystems */
struct list_head subsys_list;
/* A list running through the active hierarchies */
struct list_head root_list;
- /* All cgroups on this root, cgroup_mutex protected */
- struct list_head allcg_list;
-
/* Hierarchy-specific flags */
unsigned long flags;
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
+ * List of cgrp_cset_links pointing at cgroups referenced from this
+ * css_set. Protected by css_set_lock.
*/
- struct list_head cg_links;
+ struct list_head cgrp_links;
/*
* Set of subsystem states, one for each subsystem. This array
*/
/* cftype->flags */
-#define CFTYPE_ONLY_ON_ROOT (1U << 0) /* only create on root cg */
-#define CFTYPE_NOT_ON_ROOT (1U << 1) /* don't create on root cg */
-#define CFTYPE_INSANE (1U << 2) /* don't create if sane_behavior */
+enum {
+ CFTYPE_ONLY_ON_ROOT = (1 << 0), /* only create on root cg */
+ CFTYPE_NOT_ON_ROOT = (1 << 1), /* don't create on root cg */
+ CFTYPE_INSANE = (1 << 2), /* don't create if sane_behavior */
+};
#define MAX_CFTYPE_NAME 64
* entry. The key/value pairs (and their ordering) should not
* change between reboots.
*/
- int (*read_map)(struct cgroup *cont, struct cftype *cft,
+ int (*read_map)(struct cgroup *cgrp, 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,
+ int (*read_seq_string)(struct cgroup *cgrp, struct cftype *cft,
struct seq_file *m);
ssize_t (*write)(struct cgroup *cgrp, struct cftype *cft,
int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
-int cgroup_is_removed(const struct cgroup *cgrp);
bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
+int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
int cgroup_task_count(const struct cgroup *cgrp);
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.
+/**
+ * task_css_set_check - obtain a task's css_set with extra access conditions
+ * @task: the task to obtain css_set for
+ * @__c: extra condition expression to be passed to rcu_dereference_check()
+ *
+ * A task's css_set is RCU protected, initialized and exited while holding
+ * task_lock(), and can only be modified while holding both cgroup_mutex
+ * and task_lock() while the task is alive. This macro verifies that the
+ * caller is inside proper critical section and returns @task's css_set.
+ *
+ * The caller can also specify additional allowed conditions via @__c, such
+ * as locks used during the cgroup_subsys::attach() methods.
*/
#ifdef CONFIG_PROVE_RCU
extern struct mutex cgroup_mutex;
-#define task_subsys_state_check(task, subsys_id, __c) \
- rcu_dereference_check((task)->cgroups->subsys[(subsys_id)], \
- lockdep_is_held(&(task)->alloc_lock) || \
- lockdep_is_held(&cgroup_mutex) || (__c))
+#define task_css_set_check(task, __c) \
+ rcu_dereference_check((task)->cgroups, \
+ lockdep_is_held(&(task)->alloc_lock) || \
+ lockdep_is_held(&cgroup_mutex) || (__c))
#else
-#define task_subsys_state_check(task, subsys_id, __c) \
- rcu_dereference((task)->cgroups->subsys[(subsys_id)])
+#define task_css_set_check(task, __c) \
+ rcu_dereference((task)->cgroups)
#endif
+/**
+ * task_subsys_state_check - obtain css for (task, subsys) w/ extra access conds
+ * @task: the target task
+ * @subsys_id: the target subsystem ID
+ * @__c: extra condition expression to be passed to rcu_dereference_check()
+ *
+ * Return the cgroup_subsys_state for the (@task, @subsys_id) pair. The
+ * synchronization rules are the same as task_css_set_check().
+ */
+#define task_subsys_state_check(task, subsys_id, __c) \
+ task_css_set_check((task), (__c))->subsys[(subsys_id)]
+
+/**
+ * task_css_set - obtain a task's css_set
+ * @task: the task to obtain css_set for
+ *
+ * See task_css_set_check().
+ */
+static inline struct css_set *task_css_set(struct task_struct *task)
+{
+ return task_css_set_check(task, false);
+}
+
+/**
+ * task_subsys_state - obtain css for (task, subsys)
+ * @task: the target task
+ * @subsys_id: the target subsystem ID
+ *
+ * See task_subsys_state_check().
+ */
static inline struct cgroup_subsys_state *
task_subsys_state(struct task_struct *task, int subsys_id)
{
return task_subsys_state(task, subsys_id)->cgroup;
}
+struct cgroup *cgroup_next_sibling(struct cgroup *pos);
+
/**
* cgroup_for_each_child - iterate through children of a cgroup
* @pos: the cgroup * to use as the loop cursor
- * @cgroup: cgroup whose children to walk
+ * @cgrp: cgroup whose children to walk
*
- * Walk @cgroup's children. Must be called under rcu_read_lock(). A child
+ * Walk @cgrp's children. Must be called under rcu_read_lock(). A child
* cgroup which hasn't finished ->css_online() or already has finished
* ->css_offline() may show up during traversal and it's each subsystem's
* responsibility to verify that each @pos is alive.
* If a subsystem synchronizes against the parent in its ->css_online() and
* before starting iterating, a cgroup which finished ->css_online() is
* guaranteed to be visible in the future iterations.
+ *
+ * It is allowed to temporarily drop RCU read lock during iteration. The
+ * caller is responsible for ensuring that @pos remains accessible until
+ * the start of the next iteration by, for example, bumping the css refcnt.
*/
-#define cgroup_for_each_child(pos, cgroup) \
- list_for_each_entry_rcu(pos, &(cgroup)->children, sibling)
+#define cgroup_for_each_child(pos, cgrp) \
+ for ((pos) = list_first_or_null_rcu(&(cgrp)->children, \
+ struct cgroup, sibling); \
+ (pos); (pos) = cgroup_next_sibling((pos)))
struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,
struct cgroup *cgroup);
* Alternatively, a subsystem may choose to use a single global lock to
* synchronize ->css_online() and ->css_offline() against tree-walking
* operations.
+ *
+ * It is allowed to temporarily drop RCU read lock during iteration. The
+ * caller is responsible for ensuring that @pos remains accessible until
+ * the start of the next iteration by, for example, bumping the css refcnt.
*/
#define cgroup_for_each_descendant_pre(pos, cgroup) \
for (pos = cgroup_next_descendant_pre(NULL, (cgroup)); (pos); \
/* A cgroup_iter should be treated as an opaque object */
struct cgroup_iter {
- struct list_head *cg_link;
+ struct list_head *cset_link;
struct list_head *task;
};
/* 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 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)
{
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