/* * cgroup_freezer.c - control group freezer subsystem * * Copyright IBM Corporation, 2007 * * Author : Cedric Le Goater <[email protected]> * * This program is free software; you can redistribute it and/or modify it * under the terms of version 2.1 of the GNU Lesser General Public License * as published by the Free Software Foundation. * * This program is distributed in the hope that it would be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. */ #include <linux/export.h> #include <linux/slab.h> #include <linux/cgroup.h> #include <linux/fs.h> #include <linux/uaccess.h> #include <linux/freezer.h> #include <linux/seq_file.h> #include <linux/mutex.h> #include <linux/cpu.h> /* * A cgroup is freezing if any FREEZING flags are set. FREEZING_SELF is * set if "FROZEN" is written to freezer.state cgroupfs file, and cleared * for "THAWED". FREEZING_PARENT is set if the parent freezer is FREEZING * for whatever reason. IOW, a cgroup has FREEZING_PARENT set if one of * its ancestors has FREEZING_SELF set. */ enum freezer_state_flags { … }; struct freezer { … }; static DEFINE_MUTEX(freezer_mutex); static inline struct freezer *css_freezer(struct cgroup_subsys_state *css) { … } static inline struct freezer *task_freezer(struct task_struct *task) { … } static struct freezer *parent_freezer(struct freezer *freezer) { … } bool cgroup_freezing(struct task_struct *task) { … } static const char *freezer_state_strs(unsigned int state) { if (state & CGROUP_FROZEN) return "FROZEN"; if (state & CGROUP_FREEZING) return "FREEZING"; return "THAWED"; }; static struct cgroup_subsys_state * freezer_css_alloc(struct cgroup_subsys_state *parent_css) { … } /** * freezer_css_online - commit creation of a freezer css * @css: css being created * * We're committing to creation of @css. Mark it online and inherit * parent's freezing state while holding cpus read lock and freezer_mutex. */ static int freezer_css_online(struct cgroup_subsys_state *css) { … } /** * freezer_css_offline - initiate destruction of a freezer css * @css: css being destroyed * * @css is going away. Mark it dead and decrement freezer_active if * it was holding one. */ static void freezer_css_offline(struct cgroup_subsys_state *css) { … } static void freezer_css_free(struct cgroup_subsys_state *css) { … } /* * Tasks can be migrated into a different freezer anytime regardless of its * current state. freezer_attach() is responsible for making new tasks * conform to the current state. * * Freezer state changes and task migration are synchronized via * @freezer->lock. freezer_attach() makes the new tasks conform to the * current state and all following state changes can see the new tasks. */ static void freezer_attach(struct cgroup_taskset *tset) { … } /** * freezer_fork - cgroup post fork callback * @task: a task which has just been forked * * @task has just been created and should conform to the current state of * the cgroup_freezer it belongs to. This function may race against * freezer_attach(). Losing to freezer_attach() means that we don't have * to do anything as freezer_attach() will put @task into the appropriate * state. */ static void freezer_fork(struct task_struct *task) { … } /** * update_if_frozen - update whether a cgroup finished freezing * @css: css of interest * * Once FREEZING is initiated, transition to FROZEN is lazily updated by * calling this function. If the current state is FREEZING but not FROZEN, * this function checks whether all tasks of this cgroup and the descendant * cgroups finished freezing and, if so, sets FROZEN. * * The caller is responsible for grabbing RCU read lock and calling * update_if_frozen() on all descendants prior to invoking this function. * * Task states and freezer state might disagree while tasks are being * migrated into or out of @css, so we can't verify task states against * @freezer state here. See freezer_attach() for details. */ static void update_if_frozen(struct cgroup_subsys_state *css) { … } static int freezer_read(struct seq_file *m, void *v) { … } static void freeze_cgroup(struct freezer *freezer) { … } static void unfreeze_cgroup(struct freezer *freezer) { … } /** * freezer_apply_state - apply state change to a single cgroup_freezer * @freezer: freezer to apply state change to * @freeze: whether to freeze or unfreeze * @state: CGROUP_FREEZING_* flag to set or clear * * Set or clear @state on @cgroup according to @freeze, and perform * freezing or thawing as necessary. */ static void freezer_apply_state(struct freezer *freezer, bool freeze, unsigned int state) { … } /** * freezer_change_state - change the freezing state of a cgroup_freezer * @freezer: freezer of interest * @freeze: whether to freeze or thaw * * Freeze or thaw @freezer according to @freeze. The operations are * recursive - all descendants of @freezer will be affected. */ static void freezer_change_state(struct freezer *freezer, bool freeze) { … } static ssize_t freezer_write(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off) { … } static u64 freezer_self_freezing_read(struct cgroup_subsys_state *css, struct cftype *cft) { … } static u64 freezer_parent_freezing_read(struct cgroup_subsys_state *css, struct cftype *cft) { … } static struct cftype files[] = …; struct cgroup_subsys freezer_cgrp_subsys = …;
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