![Tejun Heo](/assets/img/avatar_default.png)
cgroup->parent is redundant as cgroup->self.parent can also be used to determine the parent cgroup and we're moving towards using cgroup_subsys_states as the fundamental structural blocks. This patch introduces cgroup_parent() which follows cgroup->self.parent and removes cgroup->parent. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
919 lines
28 KiB
C
919 lines
28 KiB
C
#ifndef _LINUX_CGROUP_H
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#define _LINUX_CGROUP_H
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/*
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* cgroup interface
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*
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* Copyright (C) 2003 BULL SA
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* Copyright (C) 2004-2006 Silicon Graphics, Inc.
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*
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*/
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#include <linux/sched.h>
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#include <linux/cpumask.h>
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#include <linux/nodemask.h>
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#include <linux/rcupdate.h>
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#include <linux/rculist.h>
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#include <linux/cgroupstats.h>
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#include <linux/rwsem.h>
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#include <linux/idr.h>
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#include <linux/workqueue.h>
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#include <linux/fs.h>
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#include <linux/percpu-refcount.h>
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#include <linux/seq_file.h>
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#include <linux/kernfs.h>
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#include <linux/wait.h>
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#ifdef CONFIG_CGROUPS
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struct cgroup_root;
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struct cgroup_subsys;
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struct inode;
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struct cgroup;
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extern int cgroup_init_early(void);
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extern int cgroup_init(void);
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extern void cgroup_fork(struct task_struct *p);
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extern void cgroup_post_fork(struct task_struct *p);
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extern void cgroup_exit(struct task_struct *p);
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extern int cgroupstats_build(struct cgroupstats *stats,
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struct dentry *dentry);
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extern int proc_cgroup_show(struct seq_file *, void *);
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/* define the enumeration of all cgroup subsystems */
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#define SUBSYS(_x) _x ## _cgrp_id,
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enum cgroup_subsys_id {
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#include <linux/cgroup_subsys.h>
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CGROUP_SUBSYS_COUNT,
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};
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#undef SUBSYS
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/*
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* Per-subsystem/per-cgroup state maintained by the system. This is the
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* fundamental structural building block that controllers deal with.
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*
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* Fields marked with "PI:" are public and immutable and may be accessed
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* directly without synchronization.
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*/
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struct cgroup_subsys_state {
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/* PI: the cgroup that this css is attached to */
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struct cgroup *cgroup;
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/* PI: the cgroup subsystem that this css is attached to */
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struct cgroup_subsys *ss;
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/* reference count - access via css_[try]get() and css_put() */
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struct percpu_ref refcnt;
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/* PI: the parent css */
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struct cgroup_subsys_state *parent;
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/*
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* PI: Subsys-unique ID. 0 is unused and root is always 1. The
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* matching css can be looked up using css_from_id().
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*/
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int id;
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unsigned int flags;
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/* percpu_ref killing and RCU release */
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struct rcu_head rcu_head;
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struct work_struct destroy_work;
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};
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/* bits in struct cgroup_subsys_state flags field */
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enum {
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CSS_NO_REF = (1 << 0), /* no reference counting for this css */
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CSS_ONLINE = (1 << 1), /* between ->css_online() and ->css_offline() */
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};
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/**
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* css_get - obtain a reference on the specified css
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* @css: target css
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*
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* The caller must already have a reference.
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*/
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static inline void css_get(struct cgroup_subsys_state *css)
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{
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if (!(css->flags & CSS_NO_REF))
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percpu_ref_get(&css->refcnt);
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}
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/**
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* css_tryget_online - try to obtain a reference on the specified css if online
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* @css: target css
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*
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* Obtain a reference on @css if it's online. The caller naturally needs
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* to ensure that @css is accessible but doesn't have to be holding a
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* reference on it - IOW, RCU protected access is good enough for this
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* function. Returns %true if a reference count was successfully obtained;
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* %false otherwise.
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*/
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static inline bool css_tryget_online(struct cgroup_subsys_state *css)
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{
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if (!(css->flags & CSS_NO_REF))
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return percpu_ref_tryget_live(&css->refcnt);
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return true;
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}
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/**
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* css_put - put a css reference
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* @css: target css
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*
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* Put a reference obtained via css_get() and css_tryget_online().
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*/
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static inline void css_put(struct cgroup_subsys_state *css)
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{
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if (!(css->flags & CSS_NO_REF))
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percpu_ref_put(&css->refcnt);
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}
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/* bits in struct cgroup flags field */
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enum {
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/* Control Group is dead */
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CGRP_DEAD,
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/*
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* Control Group has previously had a child cgroup or a task,
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* but no longer (only if CGRP_NOTIFY_ON_RELEASE is set)
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*/
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CGRP_RELEASABLE,
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/* Control Group requires release notifications to userspace */
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CGRP_NOTIFY_ON_RELEASE,
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/*
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* Clone the parent's configuration when creating a new child
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* cpuset cgroup. For historical reasons, this option can be
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* specified at mount time and thus is implemented here.
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*/
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CGRP_CPUSET_CLONE_CHILDREN,
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};
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struct cgroup {
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/* self css with NULL ->ss, points back to this cgroup */
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struct cgroup_subsys_state self;
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unsigned long flags; /* "unsigned long" so bitops work */
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/*
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* idr allocated in-hierarchy ID.
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*
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* ID 0 is not used, the ID of the root cgroup is always 1, and a
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* new cgroup will be assigned with a smallest available ID.
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*
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* Allocating/Removing ID must be protected by cgroup_mutex.
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*/
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int id;
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/*
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* If this cgroup contains any tasks, it contributes one to
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* populated_cnt. All children with non-zero popuplated_cnt of
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* their own contribute one. The count is zero iff there's no task
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* in this cgroup or its subtree.
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*/
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int populated_cnt;
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/*
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* We link our 'sibling' struct into our parent's 'children'.
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* Our children link their 'sibling' into our 'children'.
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*/
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struct list_head sibling; /* my parent's children */
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struct list_head children; /* my children */
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struct kernfs_node *kn; /* cgroup kernfs entry */
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struct kernfs_node *populated_kn; /* kn for "cgroup.subtree_populated" */
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/*
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* Monotonically increasing unique serial number which defines a
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* uniform order among all cgroups. It's guaranteed that all
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* ->children lists are in the ascending order of ->serial_nr.
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* It's used to allow interrupting and resuming iterations.
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*/
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u64 serial_nr;
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/* the bitmask of subsystems enabled on the child cgroups */
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unsigned int child_subsys_mask;
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/* Private pointers for each registered subsystem */
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struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT];
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struct cgroup_root *root;
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/*
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* List of cgrp_cset_links pointing at css_sets with tasks in this
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* cgroup. Protected by css_set_lock.
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*/
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struct list_head cset_links;
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/*
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* On the default hierarchy, a css_set for a cgroup with some
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* susbsys disabled will point to css's which are associated with
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* the closest ancestor which has the subsys enabled. The
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* following lists all css_sets which point to this cgroup's css
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* for the given subsystem.
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*/
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struct list_head e_csets[CGROUP_SUBSYS_COUNT];
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/*
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* Linked list running through all cgroups that can
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* potentially be reaped by the release agent. Protected by
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* release_list_lock
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*/
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struct list_head release_list;
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/*
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* list of pidlists, up to two for each namespace (one for procs, one
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* for tasks); created on demand.
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*/
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struct list_head pidlists;
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struct mutex pidlist_mutex;
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/* used to wait for offlining of csses */
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wait_queue_head_t offline_waitq;
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};
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#define MAX_CGROUP_ROOT_NAMELEN 64
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/* cgroup_root->flags */
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enum {
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/*
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* Unfortunately, cgroup core and various controllers are riddled
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* with idiosyncrasies and pointless options. The following flag,
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* when set, will force sane behavior - some options are forced on,
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* others are disallowed, and some controllers will change their
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* hierarchical or other behaviors.
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*
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* The set of behaviors affected by this flag are still being
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* determined and developed and the mount option for this flag is
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* prefixed with __DEVEL__. The prefix will be dropped once we
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* reach the point where all behaviors are compatible with the
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* planned unified hierarchy, which will automatically turn on this
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* flag.
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*
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* The followings are the behaviors currently affected this flag.
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*
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* - Mount options "noprefix", "xattr", "clone_children",
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* "release_agent" and "name" are disallowed.
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*
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* - When mounting an existing superblock, mount options should
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* match.
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*
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* - Remount is disallowed.
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*
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* - rename(2) is disallowed.
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*
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* - "tasks" is removed. Everything should be at process
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* granularity. Use "cgroup.procs" instead.
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*
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* - "cgroup.procs" is not sorted. pids will be unique unless they
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* got recycled inbetween reads.
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*
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* - "release_agent" and "notify_on_release" are removed.
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* Replacement notification mechanism will be implemented.
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*
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* - "cgroup.clone_children" is removed.
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*
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* - "cgroup.subtree_populated" is available. Its value is 0 if
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* the cgroup and its descendants contain no task; otherwise, 1.
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* The file also generates kernfs notification which can be
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* monitored through poll and [di]notify when the value of the
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* file changes.
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*
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* - If mount is requested with sane_behavior but without any
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* subsystem, the default unified hierarchy is mounted.
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*
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* - cpuset: tasks will be kept in empty cpusets when hotplug happens
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* and take masks of ancestors with non-empty cpus/mems, instead of
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* being moved to an ancestor.
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*
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* - cpuset: a task can be moved into an empty cpuset, and again it
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* takes masks of ancestors.
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*
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* - memcg: use_hierarchy is on by default and the cgroup file for
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* the flag is not created.
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*
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* - blkcg: blk-throttle becomes properly hierarchical.
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*/
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CGRP_ROOT_SANE_BEHAVIOR = (1 << 0),
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CGRP_ROOT_NOPREFIX = (1 << 1), /* mounted subsystems have no named prefix */
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CGRP_ROOT_XATTR = (1 << 2), /* supports extended attributes */
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/* mount options live below bit 16 */
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CGRP_ROOT_OPTION_MASK = (1 << 16) - 1,
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};
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/*
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* A cgroup_root represents the root of a cgroup hierarchy, and may be
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* associated with a kernfs_root to form an active hierarchy. This is
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* internal to cgroup core. Don't access directly from controllers.
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*/
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struct cgroup_root {
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struct kernfs_root *kf_root;
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/* The bitmask of subsystems attached to this hierarchy */
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unsigned int subsys_mask;
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/* Unique id for this hierarchy. */
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int hierarchy_id;
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/* The root cgroup. Root is destroyed on its release. */
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struct cgroup cgrp;
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/* Number of cgroups in the hierarchy, used only for /proc/cgroups */
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atomic_t nr_cgrps;
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/* A list running through the active hierarchies */
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struct list_head root_list;
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/* Hierarchy-specific flags */
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unsigned int flags;
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/* IDs for cgroups in this hierarchy */
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struct idr cgroup_idr;
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/* The path to use for release notifications. */
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char release_agent_path[PATH_MAX];
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/* The name for this hierarchy - may be empty */
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char name[MAX_CGROUP_ROOT_NAMELEN];
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};
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/*
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* A css_set is a structure holding pointers to a set of
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* cgroup_subsys_state objects. This saves space in the task struct
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* object and speeds up fork()/exit(), since a single inc/dec and a
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* list_add()/del() can bump the reference count on the entire cgroup
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* set for a task.
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*/
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struct css_set {
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/* Reference count */
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atomic_t refcount;
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/*
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* List running through all cgroup groups in the same hash
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* slot. Protected by css_set_lock
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*/
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struct hlist_node hlist;
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/*
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* Lists running through all tasks using this cgroup group.
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* mg_tasks lists tasks which belong to this cset but are in the
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* process of being migrated out or in. Protected by
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* css_set_rwsem, but, during migration, once tasks are moved to
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* mg_tasks, it can be read safely while holding cgroup_mutex.
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*/
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struct list_head tasks;
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struct list_head mg_tasks;
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/*
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* List of cgrp_cset_links pointing at cgroups referenced from this
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* css_set. Protected by css_set_lock.
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*/
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struct list_head cgrp_links;
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/* the default cgroup associated with this css_set */
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struct cgroup *dfl_cgrp;
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/*
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* Set of subsystem states, one for each subsystem. This array is
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* immutable after creation apart from the init_css_set during
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* subsystem registration (at boot time).
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*/
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struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
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/*
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* List of csets participating in the on-going migration either as
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* source or destination. Protected by cgroup_mutex.
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*/
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struct list_head mg_preload_node;
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struct list_head mg_node;
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/*
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* If this cset is acting as the source of migration the following
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* two fields are set. mg_src_cgrp is the source cgroup of the
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* on-going migration and mg_dst_cset is the destination cset the
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* target tasks on this cset should be migrated to. Protected by
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* cgroup_mutex.
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*/
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struct cgroup *mg_src_cgrp;
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struct css_set *mg_dst_cset;
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/*
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* On the default hierarhcy, ->subsys[ssid] may point to a css
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* attached to an ancestor instead of the cgroup this css_set is
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* associated with. The following node is anchored at
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* ->subsys[ssid]->cgroup->e_csets[ssid] and provides a way to
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* iterate through all css's attached to a given cgroup.
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*/
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struct list_head e_cset_node[CGROUP_SUBSYS_COUNT];
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/* For RCU-protected deletion */
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struct rcu_head rcu_head;
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};
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/*
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* struct cftype: handler definitions for cgroup control files
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*
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* When reading/writing to a file:
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* - the cgroup to use is file->f_dentry->d_parent->d_fsdata
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* - the 'cftype' of the file is file->f_dentry->d_fsdata
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*/
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/* cftype->flags */
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enum {
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CFTYPE_ONLY_ON_ROOT = (1 << 0), /* only create on root cgrp */
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CFTYPE_NOT_ON_ROOT = (1 << 1), /* don't create on root cgrp */
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CFTYPE_INSANE = (1 << 2), /* don't create if sane_behavior */
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CFTYPE_NO_PREFIX = (1 << 3), /* (DON'T USE FOR NEW FILES) no subsys prefix */
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CFTYPE_ONLY_ON_DFL = (1 << 4), /* only on default hierarchy */
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};
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#define MAX_CFTYPE_NAME 64
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struct cftype {
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/*
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* By convention, the name should begin with the name of the
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* subsystem, followed by a period. Zero length string indicates
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* end of cftype array.
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*/
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char name[MAX_CFTYPE_NAME];
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int private;
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/*
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* If not 0, file mode is set to this value, otherwise it will
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* be figured out automatically
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*/
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umode_t mode;
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/*
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* The maximum length of string, excluding trailing nul, that can
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* be passed to write. If < PAGE_SIZE-1, PAGE_SIZE-1 is assumed.
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*/
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size_t max_write_len;
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/* CFTYPE_* flags */
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unsigned int flags;
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/*
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* Fields used for internal bookkeeping. Initialized automatically
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* during registration.
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*/
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struct cgroup_subsys *ss; /* NULL for cgroup core files */
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struct list_head node; /* anchored at ss->cfts */
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struct kernfs_ops *kf_ops;
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/*
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* read_u64() is a shortcut for the common case of returning a
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* single integer. Use it in place of read()
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*/
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u64 (*read_u64)(struct cgroup_subsys_state *css, struct cftype *cft);
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/*
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* read_s64() is a signed version of read_u64()
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*/
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s64 (*read_s64)(struct cgroup_subsys_state *css, struct cftype *cft);
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/* generic seq_file read interface */
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int (*seq_show)(struct seq_file *sf, void *v);
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/* optional ops, implement all or none */
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void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
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void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
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void (*seq_stop)(struct seq_file *sf, void *v);
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/*
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* write_u64() is a shortcut for the common case of accepting
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* a single integer (as parsed by simple_strtoull) from
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* userspace. Use in place of write(); return 0 or error.
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*/
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int (*write_u64)(struct cgroup_subsys_state *css, struct cftype *cft,
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u64 val);
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/*
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* write_s64() is a signed version of write_u64()
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*/
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int (*write_s64)(struct cgroup_subsys_state *css, struct cftype *cft,
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s64 val);
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/*
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* write() is the generic write callback which maps directly to
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* kernfs write operation and overrides all other operations.
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* Maximum write size is determined by ->max_write_len. Use
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* of_css/cft() to access the associated css and cft.
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*/
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ssize_t (*write)(struct kernfs_open_file *of,
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char *buf, size_t nbytes, loff_t off);
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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struct lock_class_key lockdep_key;
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#endif
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};
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extern struct cgroup_root cgrp_dfl_root;
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extern struct css_set init_css_set;
|
|
|
|
static inline bool cgroup_on_dfl(const struct cgroup *cgrp)
|
|
{
|
|
return cgrp->root == &cgrp_dfl_root;
|
|
}
|
|
|
|
/*
|
|
* See the comment above CGRP_ROOT_SANE_BEHAVIOR for details. This
|
|
* function can be called as long as @cgrp is accessible.
|
|
*/
|
|
static inline bool cgroup_sane_behavior(const struct cgroup *cgrp)
|
|
{
|
|
return cgrp->root->flags & CGRP_ROOT_SANE_BEHAVIOR;
|
|
}
|
|
|
|
/* no synchronization, the result can only be used as a hint */
|
|
static inline bool cgroup_has_tasks(struct cgroup *cgrp)
|
|
{
|
|
return !list_empty(&cgrp->cset_links);
|
|
}
|
|
|
|
/* returns ino associated with a cgroup, 0 indicates unmounted root */
|
|
static inline ino_t cgroup_ino(struct cgroup *cgrp)
|
|
{
|
|
if (cgrp->kn)
|
|
return cgrp->kn->ino;
|
|
else
|
|
return 0;
|
|
}
|
|
|
|
/* cft/css accessors for cftype->write() operation */
|
|
static inline struct cftype *of_cft(struct kernfs_open_file *of)
|
|
{
|
|
return of->kn->priv;
|
|
}
|
|
|
|
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
|
|
* counterparts and can be called under any context.
|
|
*/
|
|
|
|
static inline int cgroup_name(struct cgroup *cgrp, char *buf, size_t buflen)
|
|
{
|
|
return kernfs_name(cgrp->kn, buf, buflen);
|
|
}
|
|
|
|
static inline char * __must_check cgroup_path(struct cgroup *cgrp, char *buf,
|
|
size_t buflen)
|
|
{
|
|
return kernfs_path(cgrp->kn, buf, buflen);
|
|
}
|
|
|
|
static inline void pr_cont_cgroup_name(struct cgroup *cgrp)
|
|
{
|
|
pr_cont_kernfs_name(cgrp->kn);
|
|
}
|
|
|
|
static inline void pr_cont_cgroup_path(struct cgroup *cgrp)
|
|
{
|
|
pr_cont_kernfs_path(cgrp->kn);
|
|
}
|
|
|
|
char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
|
|
|
|
int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
|
|
int cgroup_rm_cftypes(struct cftype *cfts);
|
|
|
|
bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
|
|
|
|
/*
|
|
* Control Group taskset, used to pass around set of tasks to cgroup_subsys
|
|
* methods.
|
|
*/
|
|
struct cgroup_taskset;
|
|
struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
|
|
struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
|
|
|
|
/**
|
|
* cgroup_taskset_for_each - iterate cgroup_taskset
|
|
* @task: the loop cursor
|
|
* @tset: taskset to iterate
|
|
*/
|
|
#define cgroup_taskset_for_each(task, tset) \
|
|
for ((task) = cgroup_taskset_first((tset)); (task); \
|
|
(task) = cgroup_taskset_next((tset)))
|
|
|
|
/*
|
|
* Control Group subsystem type.
|
|
* See Documentation/cgroups/cgroups.txt for details
|
|
*/
|
|
|
|
struct cgroup_subsys {
|
|
struct cgroup_subsys_state *(*css_alloc)(struct cgroup_subsys_state *parent_css);
|
|
int (*css_online)(struct cgroup_subsys_state *css);
|
|
void (*css_offline)(struct cgroup_subsys_state *css);
|
|
void (*css_free)(struct cgroup_subsys_state *css);
|
|
|
|
int (*can_attach)(struct cgroup_subsys_state *css,
|
|
struct cgroup_taskset *tset);
|
|
void (*cancel_attach)(struct cgroup_subsys_state *css,
|
|
struct cgroup_taskset *tset);
|
|
void (*attach)(struct cgroup_subsys_state *css,
|
|
struct cgroup_taskset *tset);
|
|
void (*fork)(struct task_struct *task);
|
|
void (*exit)(struct cgroup_subsys_state *css,
|
|
struct cgroup_subsys_state *old_css,
|
|
struct task_struct *task);
|
|
void (*bind)(struct cgroup_subsys_state *root_css);
|
|
|
|
int disabled;
|
|
int early_init;
|
|
|
|
/*
|
|
* If %false, this subsystem is properly hierarchical -
|
|
* configuration, resource accounting and restriction on a parent
|
|
* cgroup cover those of its children. If %true, hierarchy support
|
|
* is broken in some ways - some subsystems ignore hierarchy
|
|
* completely while others are only implemented half-way.
|
|
*
|
|
* It's now disallowed to create nested cgroups if the subsystem is
|
|
* broken and cgroup core will emit a warning message on such
|
|
* cases. Eventually, all subsystems will be made properly
|
|
* hierarchical and this will go away.
|
|
*/
|
|
bool broken_hierarchy;
|
|
bool warned_broken_hierarchy;
|
|
|
|
/* the following two fields are initialized automtically during boot */
|
|
int id;
|
|
#define MAX_CGROUP_TYPE_NAMELEN 32
|
|
const char *name;
|
|
|
|
/* 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.
|
|
*/
|
|
struct list_head cfts;
|
|
|
|
/* base cftypes, automatically registered with subsys itself */
|
|
struct cftype *base_cftypes;
|
|
};
|
|
|
|
#define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys;
|
|
#include <linux/cgroup_subsys.h>
|
|
#undef SUBSYS
|
|
|
|
/**
|
|
* 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;
|
|
extern struct rw_semaphore css_set_rwsem;
|
|
#define task_css_set_check(task, __c) \
|
|
rcu_dereference_check((task)->cgroups, \
|
|
lockdep_is_held(&cgroup_mutex) || \
|
|
lockdep_is_held(&css_set_rwsem) || \
|
|
((task)->flags & PF_EXITING) || (__c))
|
|
#else
|
|
#define task_css_set_check(task, __c) \
|
|
rcu_dereference((task)->cgroups)
|
|
#endif
|
|
|
|
/**
|
|
* task_css_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_css_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_css - obtain css for (task, subsys)
|
|
* @task: the target task
|
|
* @subsys_id: the target subsystem ID
|
|
*
|
|
* See task_css_check().
|
|
*/
|
|
static inline struct cgroup_subsys_state *task_css(struct task_struct *task,
|
|
int subsys_id)
|
|
{
|
|
return task_css_check(task, subsys_id, false);
|
|
}
|
|
|
|
/**
|
|
* task_css_is_root - test whether a task belongs to the root css
|
|
* @task: the target task
|
|
* @subsys_id: the target subsystem ID
|
|
*
|
|
* Test whether @task belongs to the root css on the specified subsystem.
|
|
* May be invoked in any context.
|
|
*/
|
|
static inline bool task_css_is_root(struct task_struct *task, int subsys_id)
|
|
{
|
|
return task_css_check(task, subsys_id, true) ==
|
|
init_css_set.subsys[subsys_id];
|
|
}
|
|
|
|
static inline struct cgroup *task_cgroup(struct task_struct *task,
|
|
int subsys_id)
|
|
{
|
|
return task_css(task, subsys_id)->cgroup;
|
|
}
|
|
|
|
struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
|
|
struct cgroup_subsys_state *parent);
|
|
|
|
struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);
|
|
|
|
/**
|
|
* css_for_each_child - iterate through children of a css
|
|
* @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.
|
|
*
|
|
* 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.
|
|
*
|
|
* 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 css_for_each_child(pos, parent) \
|
|
for ((pos) = css_next_child(NULL, (parent)); (pos); \
|
|
(pos) = css_next_child((pos), (parent)))
|
|
|
|
struct cgroup_subsys_state *
|
|
css_next_descendant_pre(struct cgroup_subsys_state *pos,
|
|
struct cgroup_subsys_state *css);
|
|
|
|
struct cgroup_subsys_state *
|
|
css_rightmost_descendant(struct cgroup_subsys_state *pos);
|
|
|
|
/**
|
|
* css_for_each_descendant_pre - pre-order walk of a css's descendants
|
|
* @pos: the css * to use as the loop cursor
|
|
* @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.
|
|
*
|
|
* 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.
|
|
*
|
|
* In other words, the following guarantees that a descendant can't escape
|
|
* state updates of its ancestors.
|
|
*
|
|
* my_online(@css)
|
|
* {
|
|
* Lock @css's parent and @css;
|
|
* Inherit state from the parent;
|
|
* Unlock both.
|
|
* }
|
|
*
|
|
* my_update_state(@css)
|
|
* {
|
|
* css_for_each_descendant_pre(@pos, @css) {
|
|
* Lock @pos;
|
|
* if (@pos == @css)
|
|
* Update @css's state;
|
|
* else
|
|
* Verify @pos is alive and inherit state from its parent;
|
|
* Unlock @pos;
|
|
* }
|
|
* }
|
|
*
|
|
* As long as the inheriting step, including checking the parent state, is
|
|
* enclosed inside @pos locking, double-locking the parent isn't necessary
|
|
* while inheriting. The state update to the parent is guaranteed to be
|
|
* visible by walking order and, as long as inheriting operations to the
|
|
* same @pos are atomic to each other, multiple updates racing each other
|
|
* still result in the correct state. It's guaranateed that at least one
|
|
* inheritance happens for any css after the latest update to its parent.
|
|
*
|
|
* If checking parent's state requires locking the parent, each inheriting
|
|
* iteration should lock and unlock both @pos->parent and @pos.
|
|
*
|
|
* 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 css_for_each_descendant_pre(pos, css) \
|
|
for ((pos) = css_next_descendant_pre(NULL, (css)); (pos); \
|
|
(pos) = css_next_descendant_pre((pos), (css)))
|
|
|
|
struct cgroup_subsys_state *
|
|
css_next_descendant_post(struct cgroup_subsys_state *pos,
|
|
struct cgroup_subsys_state *css);
|
|
|
|
/**
|
|
* css_for_each_descendant_post - post-order walk of a css's descendants
|
|
* @pos: the css * to use as the loop cursor
|
|
* @css: css whose descendants to walk
|
|
*
|
|
* 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.
|
|
*/
|
|
#define css_for_each_descendant_post(pos, css) \
|
|
for ((pos) = css_next_descendant_post(NULL, (css)); (pos); \
|
|
(pos) = css_next_descendant_post((pos), (css)))
|
|
|
|
/* A css_task_iter should be treated as an opaque object */
|
|
struct css_task_iter {
|
|
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,
|
|
struct css_task_iter *it);
|
|
struct task_struct *css_task_iter_next(struct css_task_iter *it);
|
|
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_online_from_dir(struct dentry *dentry,
|
|
struct cgroup_subsys *ss);
|
|
|
|
#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_post_fork(struct task_struct *p) {}
|
|
static inline void cgroup_exit(struct task_struct *p) {}
|
|
|
|
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;
|
|
}
|
|
|
|
#endif /* !CONFIG_CGROUPS */
|
|
|
|
#endif /* _LINUX_CGROUP_H */
|