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![Linus Torvalds](/assets/img/avatar_default.png)
Pull cgroup updates from Tejun Heo: - threadgroup_lock got reorganized so that its users can pick the actual locking mechanism to use. Its only user - cgroups - is updated to use a percpu_rwsem instead of per-process rwsem. This makes things a bit lighter on hot paths and allows cgroups to perform and fail multi-task (a process) migrations atomically. Multi-task migrations are used in several places including the unified hierarchy. - Delegation rule and documentation added to unified hierarchy. This will likely be the last interface update from the cgroup core side for unified hierarchy before lifting the devel mask. - Some groundwork for the pids controller which is scheduled to be merged in the coming devel cycle. * 'for-4.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: cgroup: add delegation section to unified hierarchy documentation cgroup: require write perm on common ancestor when moving processes on the default hierarchy cgroup: separate out cgroup_procs_write_permission() from __cgroup_procs_write() kernfs: make kernfs_get_inode() public MAINTAINERS: add a cgroup core co-maintainer cgroup: fix uninitialised iterator in for_each_subsys_which cgroup: replace explicit ss_mask checking with for_each_subsys_which cgroup: use bitmask to filter for_each_subsys cgroup: add seq_file forward declaration for struct cftype cgroup: simplify threadgroup locking sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem sched, cgroup: reorganize threadgroup locking cgroup: switch to unsigned long for bitmasks cgroup: reorganize include/linux/cgroup.h cgroup: separate out include/linux/cgroup-defs.h cgroup: fix some comment typos
535 lines
17 KiB
C
535 lines
17 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/rculist.h>
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#include <linux/cgroupstats.h>
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#include <linux/rwsem.h>
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#include <linux/fs.h>
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#include <linux/seq_file.h>
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#include <linux/kernfs.h>
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#include <linux/cgroup-defs.h>
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#ifdef CONFIG_CGROUPS
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/* a css_task_iter should be treated as an opaque object */
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struct css_task_iter {
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struct cgroup_subsys *ss;
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struct list_head *cset_pos;
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struct list_head *cset_head;
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struct list_head *task_pos;
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struct list_head *tasks_head;
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struct list_head *mg_tasks_head;
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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;
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#define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys;
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#include <linux/cgroup_subsys.h>
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#undef SUBSYS
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bool css_has_online_children(struct cgroup_subsys_state *css);
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struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);
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struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup,
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struct cgroup_subsys *ss);
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struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
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struct cgroup_subsys *ss);
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bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
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int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
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int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
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int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
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int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
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int cgroup_rm_cftypes(struct cftype *cfts);
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char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
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int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry);
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int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
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struct pid *pid, struct task_struct *tsk);
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void cgroup_fork(struct task_struct *p);
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void cgroup_post_fork(struct task_struct *p);
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void cgroup_exit(struct task_struct *p);
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int cgroup_init_early(void);
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int cgroup_init(void);
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/*
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* Iteration helpers and macros.
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*/
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struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
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struct cgroup_subsys_state *parent);
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struct cgroup_subsys_state *css_next_descendant_pre(struct cgroup_subsys_state *pos,
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struct cgroup_subsys_state *css);
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struct cgroup_subsys_state *css_rightmost_descendant(struct cgroup_subsys_state *pos);
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struct cgroup_subsys_state *css_next_descendant_post(struct cgroup_subsys_state *pos,
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struct cgroup_subsys_state *css);
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struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
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struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
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void css_task_iter_start(struct cgroup_subsys_state *css,
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struct css_task_iter *it);
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struct task_struct *css_task_iter_next(struct css_task_iter *it);
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void css_task_iter_end(struct css_task_iter *it);
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/**
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* css_for_each_child - iterate through children of a css
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* @pos: the css * to use as the loop cursor
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* @parent: css whose children to walk
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*
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* Walk @parent's children. Must be called under rcu_read_lock().
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*
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* If a subsystem synchronizes ->css_online() and the start of iteration, a
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* css which finished ->css_online() is guaranteed to be visible in the
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* future iterations and will stay visible until the last reference is put.
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* A css which hasn't finished ->css_online() or already finished
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* ->css_offline() may show up during traversal. It's each subsystem's
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* responsibility to synchronize against on/offlining.
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*
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* It is allowed to temporarily drop RCU read lock during iteration. The
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* caller is responsible for ensuring that @pos remains accessible until
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* the start of the next iteration by, for example, bumping the css refcnt.
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*/
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#define css_for_each_child(pos, parent) \
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for ((pos) = css_next_child(NULL, (parent)); (pos); \
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(pos) = css_next_child((pos), (parent)))
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/**
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* css_for_each_descendant_pre - pre-order walk of a css's descendants
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* @pos: the css * to use as the loop cursor
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* @root: css whose descendants to walk
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*
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* Walk @root's descendants. @root is included in the iteration and the
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* first node to be visited. Must be called under rcu_read_lock().
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*
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* If a subsystem synchronizes ->css_online() and the start of iteration, a
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* css which finished ->css_online() is guaranteed to be visible in the
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* future iterations and will stay visible until the last reference is put.
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* A css which hasn't finished ->css_online() or already finished
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* ->css_offline() may show up during traversal. It's each subsystem's
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* responsibility to synchronize against on/offlining.
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*
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* For example, the following guarantees that a descendant can't escape
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* state updates of its ancestors.
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*
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* my_online(@css)
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* {
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* Lock @css's parent and @css;
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* Inherit state from the parent;
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* Unlock both.
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* }
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*
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* my_update_state(@css)
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* {
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* css_for_each_descendant_pre(@pos, @css) {
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* Lock @pos;
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* if (@pos == @css)
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* Update @css's state;
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* else
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* Verify @pos is alive and inherit state from its parent;
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* Unlock @pos;
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* }
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* }
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*
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* As long as the inheriting step, including checking the parent state, is
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* enclosed inside @pos locking, double-locking the parent isn't necessary
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* while inheriting. The state update to the parent is guaranteed to be
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* visible by walking order and, as long as inheriting operations to the
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* same @pos are atomic to each other, multiple updates racing each other
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* still result in the correct state. It's guaranateed that at least one
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* inheritance happens for any css after the latest update to its parent.
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*
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* If checking parent's state requires locking the parent, each inheriting
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* iteration should lock and unlock both @pos->parent and @pos.
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*
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* Alternatively, a subsystem may choose to use a single global lock to
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* synchronize ->css_online() and ->css_offline() against tree-walking
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* operations.
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*
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* It is allowed to temporarily drop RCU read lock during iteration. The
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* caller is responsible for ensuring that @pos remains accessible until
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* the start of the next iteration by, for example, bumping the css refcnt.
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*/
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#define css_for_each_descendant_pre(pos, css) \
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for ((pos) = css_next_descendant_pre(NULL, (css)); (pos); \
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(pos) = css_next_descendant_pre((pos), (css)))
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/**
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* css_for_each_descendant_post - post-order walk of a css's descendants
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* @pos: the css * to use as the loop cursor
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* @css: css whose descendants to walk
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*
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* Similar to css_for_each_descendant_pre() but performs post-order
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* traversal instead. @root is included in the iteration and the last
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* node to be visited.
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*
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* If a subsystem synchronizes ->css_online() and the start of iteration, a
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* css which finished ->css_online() is guaranteed to be visible in the
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* future iterations and will stay visible until the last reference is put.
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* A css which hasn't finished ->css_online() or already finished
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* ->css_offline() may show up during traversal. It's each subsystem's
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* responsibility to synchronize against on/offlining.
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*
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* Note that the walk visibility guarantee example described in pre-order
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* walk doesn't apply the same to post-order walks.
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*/
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#define css_for_each_descendant_post(pos, css) \
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for ((pos) = css_next_descendant_post(NULL, (css)); (pos); \
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(pos) = css_next_descendant_post((pos), (css)))
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/**
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* cgroup_taskset_for_each - iterate cgroup_taskset
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* @task: the loop cursor
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* @tset: taskset to iterate
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*/
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#define cgroup_taskset_for_each(task, tset) \
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for ((task) = cgroup_taskset_first((tset)); (task); \
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(task) = cgroup_taskset_next((tset)))
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/*
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* Inline functions.
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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_get_many - obtain references on the specified css
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* @css: target css
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* @n: number of references to get
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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_many(struct cgroup_subsys_state *css, unsigned int n)
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{
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if (!(css->flags & CSS_NO_REF))
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percpu_ref_get_many(&css->refcnt, n);
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}
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/**
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* css_tryget - try to obtain a reference on the specified css
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* @css: target css
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*
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* Obtain a reference on @css unless it already has reached zero and is
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* being released. This function doesn't care whether @css is on or
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* offline. The caller naturally needs to ensure that @css is accessible
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* but doesn't have to be holding a reference on it - IOW, RCU protected
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* access is good enough for this function. Returns %true if a reference
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* count was successfully obtained; %false otherwise.
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*/
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static inline bool css_tryget(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(&css->refcnt);
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return true;
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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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/**
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* css_put_many - put css references
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* @css: target css
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* @n: number of references to put
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*
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* Put references obtained via css_get() and css_tryget_online().
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*/
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static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n)
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{
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if (!(css->flags & CSS_NO_REF))
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percpu_ref_put_many(&css->refcnt, n);
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}
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/**
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* task_css_set_check - obtain a task's css_set with extra access conditions
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* @task: the task to obtain css_set for
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* @__c: extra condition expression to be passed to rcu_dereference_check()
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*
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* A task's css_set is RCU protected, initialized and exited while holding
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* task_lock(), and can only be modified while holding both cgroup_mutex
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* and task_lock() while the task is alive. This macro verifies that the
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* caller is inside proper critical section and returns @task's css_set.
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*
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* The caller can also specify additional allowed conditions via @__c, such
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* as locks used during the cgroup_subsys::attach() methods.
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*/
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#ifdef CONFIG_PROVE_RCU
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extern struct mutex cgroup_mutex;
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extern struct rw_semaphore css_set_rwsem;
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#define task_css_set_check(task, __c) \
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rcu_dereference_check((task)->cgroups, \
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lockdep_is_held(&cgroup_mutex) || \
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lockdep_is_held(&css_set_rwsem) || \
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((task)->flags & PF_EXITING) || (__c))
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#else
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#define task_css_set_check(task, __c) \
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rcu_dereference((task)->cgroups)
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#endif
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/**
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* task_css_check - obtain css for (task, subsys) w/ extra access conds
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* @task: the target task
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* @subsys_id: the target subsystem ID
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* @__c: extra condition expression to be passed to rcu_dereference_check()
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*
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* Return the cgroup_subsys_state for the (@task, @subsys_id) pair. The
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* synchronization rules are the same as task_css_set_check().
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*/
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#define task_css_check(task, subsys_id, __c) \
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task_css_set_check((task), (__c))->subsys[(subsys_id)]
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/**
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* task_css_set - obtain a task's css_set
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* @task: the task to obtain css_set for
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*
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* See task_css_set_check().
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*/
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static inline struct css_set *task_css_set(struct task_struct *task)
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{
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return task_css_set_check(task, false);
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}
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/**
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* task_css - obtain css for (task, subsys)
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* @task: the target task
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* @subsys_id: the target subsystem ID
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*
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* See task_css_check().
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*/
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static inline struct cgroup_subsys_state *task_css(struct task_struct *task,
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int subsys_id)
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{
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return task_css_check(task, subsys_id, false);
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}
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/**
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* task_get_css - find and get the css for (task, subsys)
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* @task: the target task
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* @subsys_id: the target subsystem ID
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*
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* Find the css for the (@task, @subsys_id) combination, increment a
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* reference on and return it. This function is guaranteed to return a
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* valid css.
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*/
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static inline struct cgroup_subsys_state *
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task_get_css(struct task_struct *task, int subsys_id)
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{
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struct cgroup_subsys_state *css;
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rcu_read_lock();
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while (true) {
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css = task_css(task, subsys_id);
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if (likely(css_tryget_online(css)))
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break;
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cpu_relax();
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}
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rcu_read_unlock();
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return css;
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}
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/**
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* task_css_is_root - test whether a task belongs to the root css
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* @task: the target task
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* @subsys_id: the target subsystem ID
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*
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* Test whether @task belongs to the root css on the specified subsystem.
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* May be invoked in any context.
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*/
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static inline bool task_css_is_root(struct task_struct *task, int subsys_id)
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{
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return task_css_check(task, subsys_id, true) ==
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init_css_set.subsys[subsys_id];
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}
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static inline struct cgroup *task_cgroup(struct task_struct *task,
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int subsys_id)
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{
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return task_css(task, subsys_id)->cgroup;
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}
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/**
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* cgroup_on_dfl - test whether a cgroup is on the default hierarchy
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* @cgrp: the cgroup of interest
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*
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* The default hierarchy is the v2 interface of cgroup and this function
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* can be used to test whether a cgroup is on the default hierarchy for
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* cases where a subsystem should behave differnetly depending on the
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* interface version.
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*
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* The set of behaviors which change on the default hierarchy are still
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* being determined and the mount option is prefixed with __DEVEL__.
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*
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* List of changed behaviors:
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*
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* - Mount options "noprefix", "xattr", "clone_children", "release_agent"
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* and "name" are disallowed.
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*
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* - When mounting an existing superblock, mount options should 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 granularity. Use
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* "cgroup.procs" instead.
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*
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* - "cgroup.procs" is not sorted. pids will be unique unless they got
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* recycled inbetween reads.
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*
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* - "release_agent" and "notify_on_release" are removed. Replacement
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* 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 the cgroup
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* and its descendants contain no task; otherwise, 1. The file also
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* generates kernfs notification which can be monitored through poll and
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* [di]notify when the value of the file changes.
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*
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* - cpuset: tasks will be kept in empty cpusets when hotplug happens and
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* take masks of ancestors with non-empty cpus/mems, instead of being
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* 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 takes
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|
* 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.
|
|
*
|
|
* - debug: disallowed on the default hierarchy.
|
|
*/
|
|
static inline bool cgroup_on_dfl(const struct cgroup *cgrp)
|
|
{
|
|
return cgrp->root == &cgrp_dfl_root;
|
|
}
|
|
|
|
/* 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 */
|
|
static inline ino_t cgroup_ino(struct cgroup *cgrp)
|
|
{
|
|
return cgrp->kn->ino;
|
|
}
|
|
|
|
/* 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);
|
|
}
|
|
|
|
#else /* !CONFIG_CGROUPS */
|
|
|
|
struct cgroup_subsys_state;
|
|
|
|
static inline void css_put(struct cgroup_subsys_state *css) {}
|
|
static inline int cgroup_attach_task_all(struct task_struct *from,
|
|
struct task_struct *t) { return 0; }
|
|
static inline int cgroupstats_build(struct cgroupstats *stats,
|
|
struct dentry *dentry) { return -EINVAL; }
|
|
|
|
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 cgroup_init_early(void) { return 0; }
|
|
static inline int cgroup_init(void) { return 0; }
|
|
|
|
#endif /* !CONFIG_CGROUPS */
|
|
|
|
#endif /* _LINUX_CGROUP_H */
|