f0d9a5f175
css_set_rwsem is the inner lock protecting css_sets and is accessed from hot paths such as fork and exit. Internally, it has no reason to be a rwsem or even mutex. There are no internal blocking operations while holding it. This was rwsem because css task iteration used to expose it to external iterator users. As the previous patch updated css task iteration such that the locking is not leaked to its users, there's no reason to keep it a rwsem. This patch converts css_set_rwsem to a spinlock and rename it to css_set_lock. It uses bh-safe operations as a planned usage needs to access it from RCU callback context. Signed-off-by: Tejun Heo <tj@kernel.org>
557 lines
18 KiB
C
557 lines
18 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/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/jump_label.h>
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#include <linux/cgroup-defs.h>
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#ifdef CONFIG_CGROUPS
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/*
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* All weight knobs on the default hierarhcy should use the following min,
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* default and max values. The default value is the logarithmic center of
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* MIN and MAX and allows 100x to be expressed in both directions.
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*/
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#define CGROUP_WEIGHT_MIN 1
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#define CGROUP_WEIGHT_DFL 100
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#define CGROUP_WEIGHT_MAX 10000
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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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struct css_set *cur_cset;
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struct task_struct *cur_task;
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struct list_head iters_node; /* css_set->task_iters */
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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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#define SUBSYS(_x) \
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extern struct static_key_true _x ## _cgrp_subsys_enabled_key; \
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extern struct static_key_true _x ## _cgrp_subsys_on_dfl_key;
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#include <linux/cgroup_subsys.h>
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#undef SUBSYS
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/**
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* cgroup_subsys_enabled - fast test on whether a subsys is enabled
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* @ss: subsystem in question
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*/
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#define cgroup_subsys_enabled(ss) \
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static_branch_likely(&ss ## _enabled_key)
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/**
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* cgroup_subsys_on_dfl - fast test on whether a subsys is on default hierarchy
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* @ss: subsystem in question
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*/
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#define cgroup_subsys_on_dfl(ss) \
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static_branch_likely(&ss ## _on_dfl_key)
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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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extern int cgroup_can_fork(struct task_struct *p,
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void *ss_priv[CGROUP_CANFORK_COUNT]);
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extern void cgroup_cancel_fork(struct task_struct *p,
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void *ss_priv[CGROUP_CANFORK_COUNT]);
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extern void cgroup_post_fork(struct task_struct *p,
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void *old_ss_priv[CGROUP_CANFORK_COUNT]);
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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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* @tset may contain multiple tasks and they may belong to multiple
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* processes. When there are multiple tasks in @tset, if a task of a
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* process is in @tset, all tasks of the process are in @tset. Also, all
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* are guaranteed to share the same source and destination csses.
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*
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* Iteration is not in any specific order.
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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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* cgroup_taskset_for_each_leader - iterate group leaders in a cgroup_taskset
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* @leader: the loop cursor
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* @tset: takset to iterate
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*
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* Iterate threadgroup leaders of @tset. For single-task migrations, @tset
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* may not contain any.
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*/
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#define cgroup_taskset_for_each_leader(leader, tset) \
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for ((leader) = cgroup_taskset_first((tset)); (leader); \
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(leader) = cgroup_taskset_next((tset))) \
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if ((leader) != (leader)->group_leader) \
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; \
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else
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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 spinlock_t css_set_lock;
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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_lock) || \
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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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/* no synchronization, the result can only be used as a hint */
|
|
static inline bool cgroup_is_populated(struct cgroup *cgrp)
|
|
{
|
|
return cgrp->populated_cnt;
|
|
}
|
|
|
|
/* 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);
|
|
}
|
|
|
|
/**
|
|
* cgroup_file_notify - generate a file modified event for a cgroup_file
|
|
* @cfile: target cgroup_file
|
|
*
|
|
* @cfile must have been obtained by setting cftype->file_offset.
|
|
*/
|
|
static inline void cgroup_file_notify(struct cgroup_file *cfile)
|
|
{
|
|
/* might not have been created due to one of the CFTYPE selector flags */
|
|
if (cfile->kn)
|
|
kernfs_notify(cfile->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 int cgroup_can_fork(struct task_struct *p,
|
|
void *ss_priv[CGROUP_CANFORK_COUNT])
|
|
{ return 0; }
|
|
static inline void cgroup_cancel_fork(struct task_struct *p,
|
|
void *ss_priv[CGROUP_CANFORK_COUNT]) {}
|
|
static inline void cgroup_post_fork(struct task_struct *p,
|
|
void *ss_priv[CGROUP_CANFORK_COUNT]) {}
|
|
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 */
|