diff options
Diffstat (limited to 'include/linux/cgroup.h')
| -rw-r--r-- | include/linux/cgroup.h | 272 |
1 files changed, 169 insertions, 103 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index d60904b9e505..8a111dd42d7a 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -21,6 +21,7 @@ #include <linux/percpu-refcount.h> #include <linux/seq_file.h> #include <linux/kernfs.h> +#include <linux/wait.h> #ifdef CONFIG_CGROUPS @@ -47,21 +48,45 @@ enum cgroup_subsys_id { }; #undef SUBSYS -/* Per-subsystem/per-cgroup state maintained by the system. */ +/* + * Per-subsystem/per-cgroup state maintained by the system. This is the + * fundamental structural building block that controllers deal with. + * + * Fields marked with "PI:" are public and immutable and may be accessed + * directly without synchronization. + */ struct cgroup_subsys_state { - /* the cgroup that this css is attached to */ + /* PI: the cgroup that this css is attached to */ struct cgroup *cgroup; - /* the cgroup subsystem that this css is attached to */ + /* PI: the cgroup subsystem that this css is attached to */ struct cgroup_subsys *ss; /* reference count - access via css_[try]get() and css_put() */ struct percpu_ref refcnt; - /* the parent css */ + /* PI: the parent css */ struct cgroup_subsys_state *parent; - unsigned long flags; + /* siblings list anchored at the parent's ->children */ + struct list_head sibling; + struct list_head children; + + /* + * PI: Subsys-unique ID. 0 is unused and root is always 1. The + * matching css can be looked up using css_from_id(). + */ + int id; + + unsigned int flags; + + /* + * Monotonically increasing unique serial number which defines a + * uniform order among all csses. It's guaranteed that all + * ->children lists are in the ascending order of ->serial_nr and + * used to allow interrupting and resuming iterations. + */ + u64 serial_nr; /* percpu_ref killing and RCU release */ struct rcu_head rcu_head; @@ -70,8 +95,9 @@ struct cgroup_subsys_state { /* bits in struct cgroup_subsys_state flags field */ enum { - CSS_ROOT = (1 << 0), /* this CSS is the root of the subsystem */ + CSS_NO_REF = (1 << 0), /* no reference counting for this css */ CSS_ONLINE = (1 << 1), /* between ->css_online() and ->css_offline() */ + CSS_RELEASED = (1 << 2), /* refcnt reached zero, released */ }; /** @@ -82,8 +108,7 @@ enum { */ 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)) + if (!(css->flags & CSS_NO_REF)) percpu_ref_get(&css->refcnt); } @@ -91,35 +116,51 @@ static inline void css_get(struct cgroup_subsys_state *css) * 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 + * Obtain a reference on @css unless it already has reached zero and is + * being released. This function doesn't care whether @css is on or + * offline. 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. + */ +static inline bool css_tryget(struct cgroup_subsys_state *css) +{ + if (!(css->flags & CSS_NO_REF)) + return percpu_ref_tryget(&css->refcnt); + return true; +} + +/** + * css_tryget_online - try to obtain a reference on the specified css if online + * @css: target css + * + * Obtain a reference on @css if it's online. 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. */ -static inline bool css_tryget(struct cgroup_subsys_state *css) +static inline bool css_tryget_online(struct cgroup_subsys_state *css) { - if (css->flags & CSS_ROOT) - return true; - return percpu_ref_tryget(&css->refcnt); + if (!(css->flags & CSS_NO_REF)) + return percpu_ref_tryget_live(&css->refcnt); + return true; } /** * css_put - put a css reference * @css: target css * - * Put a reference obtained via css_get() and css_tryget(). + * Put a reference obtained via css_get() and css_tryget_online(). */ static inline void css_put(struct cgroup_subsys_state *css) { - if (!(css->flags & CSS_ROOT)) + if (!(css->flags & CSS_NO_REF)) percpu_ref_put(&css->refcnt); } /* bits in struct cgroup flags field */ enum { - /* Control Group is dead */ - CGRP_DEAD, /* * Control Group has previously had a child cgroup or a task, * but no longer (only if CGRP_NOTIFY_ON_RELEASE is set) @@ -133,48 +174,37 @@ enum { * specified at mount time and thus is implemented here. */ CGRP_CPUSET_CLONE_CHILDREN, - /* see the comment above CGRP_ROOT_SANE_BEHAVIOR for details */ - CGRP_SANE_BEHAVIOR, }; struct cgroup { + /* self css with NULL ->ss, points back to this cgroup */ + struct cgroup_subsys_state self; + unsigned long flags; /* "unsigned long" so bitops work */ /* * idr allocated in-hierarchy ID. * - * The ID of the root cgroup is always 0, and a new cgroup - * will be assigned with a smallest available ID. + * ID 0 is not used, the ID of the root cgroup is always 1, and a + * new cgroup will be assigned with a smallest available ID. * * Allocating/Removing ID must be protected by cgroup_mutex. */ int id; - /* the number of attached css's */ - int nr_css; - - atomic_t refcnt; - /* - * We link our 'sibling' struct into our parent's 'children'. - * Our children link their 'sibling' into our 'children'. + * If this cgroup contains any tasks, it contributes one to + * populated_cnt. All children with non-zero popuplated_cnt of + * their own contribute one. The count is zero iff there's no task + * in this cgroup or its subtree. */ - struct list_head sibling; /* my parent's children */ - struct list_head children; /* my children */ + int populated_cnt; - struct cgroup *parent; /* my parent */ struct kernfs_node *kn; /* cgroup kernfs entry */ + struct kernfs_node *populated_kn; /* kn for "cgroup.subtree_populated" */ - /* - * 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; - - /* The bitmask of subsystems attached to this cgroup */ - unsigned long subsys_mask; + /* the bitmask of subsystems enabled on the child cgroups */ + unsigned int child_subsys_mask; /* Private pointers for each registered subsystem */ struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT]; @@ -188,6 +218,15 @@ struct cgroup { struct list_head cset_links; /* + * On the default hierarchy, a css_set for a cgroup with some + * susbsys disabled will point to css's which are associated with + * the closest ancestor which has the subsys enabled. The + * following lists all css_sets which point to this cgroup's css + * for the given subsystem. + */ + struct list_head e_csets[CGROUP_SUBSYS_COUNT]; + + /* * Linked list running through all cgroups that can * potentially be reaped by the release agent. Protected by * release_list_lock @@ -201,12 +240,8 @@ struct cgroup { struct list_head pidlists; struct mutex pidlist_mutex; - /* dummy css with NULL ->ss, points back to this cgroup */ - struct cgroup_subsys_state dummy_css; - - /* For css percpu_ref killing and RCU-protected deletion */ - struct rcu_head rcu_head; - struct work_struct destroy_work; + /* used to wait for offlining of csses */ + wait_queue_head_t offline_waitq; }; #define MAX_CGROUP_ROOT_NAMELEN 64 @@ -250,6 +285,12 @@ enum { * * - "cgroup.clone_children" is removed. * + * - "cgroup.subtree_populated" is available. Its value is 0 if + * the cgroup and its descendants contain no task; otherwise, 1. + * The file also generates kernfs notification which can be + * monitored through poll and [di]notify when the value of the + * file changes. + * * - If mount is requested with sane_behavior but without any * subsystem, the default unified hierarchy is mounted. * @@ -264,6 +305,8 @@ enum { * the flag is not created. * * - blkcg: blk-throttle becomes properly hierarchical. + * + * - debug: disallowed on the default hierarchy. */ CGRP_ROOT_SANE_BEHAVIOR = (1 << 0), @@ -282,6 +325,9 @@ enum { struct cgroup_root { struct kernfs_root *kf_root; + /* The bitmask of subsystems attached to this hierarchy */ + unsigned int subsys_mask; + /* Unique id for this hierarchy. */ int hierarchy_id; @@ -295,7 +341,7 @@ struct cgroup_root { struct list_head root_list; /* Hierarchy-specific flags */ - unsigned long flags; + unsigned int flags; /* IDs for cgroups in this hierarchy */ struct idr cgroup_idr; @@ -342,6 +388,9 @@ struct css_set { */ struct list_head cgrp_links; + /* the default cgroup associated with this css_set */ + struct cgroup *dfl_cgrp; + /* * Set of subsystem states, one for each subsystem. This array is * immutable after creation apart from the init_css_set during @@ -366,6 +415,15 @@ struct css_set { struct cgroup *mg_src_cgrp; struct css_set *mg_dst_cset; + /* + * On the default hierarhcy, ->subsys[ssid] may point to a css + * attached to an ancestor instead of the cgroup this css_set is + * associated with. The following node is anchored at + * ->subsys[ssid]->cgroup->e_csets[ssid] and provides a way to + * iterate through all css's attached to a given cgroup. + */ + struct list_head e_cset_node[CGROUP_SUBSYS_COUNT]; + /* For RCU-protected deletion */ struct rcu_head rcu_head; }; @@ -405,8 +463,7 @@ struct cftype { /* * The maximum length of string, excluding trailing nul, that can - * be passed to write_string. If < PAGE_SIZE-1, PAGE_SIZE-1 is - * assumed. + * be passed to write. If < PAGE_SIZE-1, PAGE_SIZE-1 is assumed. */ size_t max_write_len; @@ -453,19 +510,13 @@ struct cftype { 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_subsys_state *css, struct cftype *cft, - 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. + * write() is the generic write callback which maps directly to + * kernfs write operation and overrides all other operations. + * Maximum write size is determined by ->max_write_len. Use + * of_css/cft() to access the associated css and cft. */ - int (*trigger)(struct cgroup_subsys_state *css, unsigned int event); + ssize_t (*write)(struct kernfs_open_file *of, + char *buf, size_t nbytes, loff_t off); #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lock_class_key lockdep_key; @@ -504,14 +555,24 @@ static inline ino_t cgroup_ino(struct cgroup *cgrp) return 0; } -static inline struct cftype *seq_cft(struct seq_file *seq) +/* cft/css accessors for cftype->write() operation */ +static inline struct cftype *of_cft(struct kernfs_open_file *of) { - struct kernfs_open_file *of = seq->private; - return of->kn->priv; } -struct cgroup_subsys_state *seq_css(struct seq_file *seq); +struct cgroup_subsys_state *of_css(struct kernfs_open_file *of); + +/* cft/css accessors for cftype->seq_*() operations */ +static inline struct cftype *seq_cft(struct seq_file *seq) +{ + return of_cft(seq->private); +} + +static inline struct cgroup_subsys_state *seq_css(struct seq_file *seq) +{ + return of_css(seq->private); +} /* * Name / path handling functions. All are thin wrappers around the kernfs @@ -612,6 +673,9 @@ struct cgroup_subsys { /* link to parent, protected by cgroup_lock() */ struct cgroup_root *root; + /* idr for css->id */ + struct idr css_idr; + /* * List of cftypes. Each entry is the first entry of an array * terminated by zero length name. @@ -627,19 +691,6 @@ struct cgroup_subsys { #undef SUBSYS /** - * css_parent - find the parent css - * @css: the target cgroup_subsys_state - * - * Return the parent css of @css. This function is guaranteed to return - * non-NULL parent as long as @css isn't the root. - */ -static inline -struct cgroup_subsys_state *css_parent(struct cgroup_subsys_state *css) -{ - return css->parent; -} - -/** * 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() @@ -731,14 +782,14 @@ struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss); * @pos: the css * to use as the loop cursor * @parent: css whose children to walk * - * Walk @parent's children. Must be called under rcu_read_lock(). A child - * css 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. + * Walk @parent's children. Must be called under rcu_read_lock(). * - * If a subsystem synchronizes against the parent in its ->css_online() and - * before starting iterating, a css which finished ->css_online() is - * guaranteed to be visible in the future iterations. + * If a subsystem synchronizes ->css_online() and the start of iteration, a + * css which finished ->css_online() is guaranteed to be visible in the + * future iterations and will stay visible until the last reference is put. + * A css which hasn't finished ->css_online() or already finished + * ->css_offline() may show up during traversal. It's each subsystem's + * responsibility to synchronize against on/offlining. * * It is allowed to temporarily drop RCU read lock during iteration. The * caller is responsible for ensuring that @pos remains accessible until @@ -761,17 +812,16 @@ css_rightmost_descendant(struct cgroup_subsys_state *pos); * @root: css whose descendants to walk * * Walk @root's descendants. @root is included in the iteration and the - * first node to be visited. Must be called under rcu_read_lock(). A - * descendant css 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. + * first node to be visited. Must be called under rcu_read_lock(). * - * If a subsystem synchronizes against the parent in its ->css_online() and - * before starting iterating, and synchronizes against @pos on each - * iteration, any descendant css which finished ->css_online() is - * guaranteed to be visible in the future iterations. + * If a subsystem synchronizes ->css_online() and the start of iteration, a + * css which finished ->css_online() is guaranteed to be visible in the + * future iterations and will stay visible until the last reference is put. + * A css which hasn't finished ->css_online() or already finished + * ->css_offline() may show up during traversal. It's each subsystem's + * responsibility to synchronize against on/offlining. * - * In other words, the following guarantees that a descendant can't escape + * For example, the following guarantees that a descendant can't escape * state updates of its ancestors. * * my_online(@css) @@ -827,18 +877,34 @@ css_next_descendant_post(struct cgroup_subsys_state *pos, * * Similar to css_for_each_descendant_pre() but performs post-order * traversal instead. @root is included in the iteration and the last - * node to be visited. Note that the walk visibility guarantee described - * in pre-order walk doesn't apply the same to post-order walks. + * node to be visited. + * + * If a subsystem synchronizes ->css_online() and the start of iteration, a + * css which finished ->css_online() is guaranteed to be visible in the + * future iterations and will stay visible until the last reference is put. + * A css which hasn't finished ->css_online() or already finished + * ->css_offline() may show up during traversal. It's each subsystem's + * responsibility to synchronize against on/offlining. + * + * Note that the walk visibility guarantee example described in pre-order + * walk doesn't apply the same to post-order walks. */ #define css_for_each_descendant_post(pos, css) \ for ((pos) = css_next_descendant_post(NULL, (css)); (pos); \ (pos) = css_next_descendant_post((pos), (css))) +bool css_has_online_children(struct cgroup_subsys_state *css); + /* A css_task_iter should be treated as an opaque object */ struct css_task_iter { - struct cgroup_subsys_state *origin_css; - struct list_head *cset_link; - struct list_head *task; + struct cgroup_subsys *ss; + + struct list_head *cset_pos; + struct list_head *cset_head; + + struct list_head *task_pos; + struct list_head *tasks_head; + struct list_head *mg_tasks_head; }; void css_task_iter_start(struct cgroup_subsys_state *css, @@ -849,8 +915,8 @@ void css_task_iter_end(struct css_task_iter *it); int cgroup_attach_task_all(struct task_struct *from, struct task_struct *); int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from); -struct cgroup_subsys_state *css_tryget_from_dir(struct dentry *dentry, - struct cgroup_subsys *ss); +struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry, + struct cgroup_subsys *ss); #else /* !CONFIG_CGROUPS */ |