diff options
author | Roman Gushchin <guro@fb.com> | 2019-04-19 20:03:01 +0300 |
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committer | Tejun Heo <tj@kernel.org> | 2019-04-19 21:26:48 +0300 |
commit | 50943f3e136adfc421f9768d6ae09ba7b83aaefd (patch) | |
tree | f1d58acef7b32badda649c9d61ccb4f82fce3387 /kernel/cgroup/legacy_freezer.c | |
parent | d6e486ee0ef2f99a4069d9186e53dac61b28cb3c (diff) | |
download | linux-50943f3e136adfc421f9768d6ae09ba7b83aaefd.tar.xz |
cgroup: rename freezer.c into legacy_freezer.c
Freezer.c will contain an implementation of cgroup v2 freezer,
so let's rename the v1 freezer to avoid naming conflicts.
Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: kernel-team@fb.com
Diffstat (limited to 'kernel/cgroup/legacy_freezer.c')
-rw-r--r-- | kernel/cgroup/legacy_freezer.c | 481 |
1 files changed, 481 insertions, 0 deletions
diff --git a/kernel/cgroup/legacy_freezer.c b/kernel/cgroup/legacy_freezer.c new file mode 100644 index 000000000000..08236798d173 --- /dev/null +++ b/kernel/cgroup/legacy_freezer.c @@ -0,0 +1,481 @@ +/* + * cgroup_freezer.c - control group freezer subsystem + * + * Copyright IBM Corporation, 2007 + * + * Author : Cedric Le Goater <clg@fr.ibm.com> + * + * 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> + +/* + * 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 { + CGROUP_FREEZER_ONLINE = (1 << 0), /* freezer is fully online */ + CGROUP_FREEZING_SELF = (1 << 1), /* this freezer is freezing */ + CGROUP_FREEZING_PARENT = (1 << 2), /* the parent freezer is freezing */ + CGROUP_FROZEN = (1 << 3), /* this and its descendants frozen */ + + /* mask for all FREEZING flags */ + CGROUP_FREEZING = CGROUP_FREEZING_SELF | CGROUP_FREEZING_PARENT, +}; + +struct freezer { + struct cgroup_subsys_state css; + unsigned int state; +}; + +static DEFINE_MUTEX(freezer_mutex); + +static inline struct freezer *css_freezer(struct cgroup_subsys_state *css) +{ + return css ? container_of(css, struct freezer, css) : NULL; +} + +static inline struct freezer *task_freezer(struct task_struct *task) +{ + return css_freezer(task_css(task, freezer_cgrp_id)); +} + +static struct freezer *parent_freezer(struct freezer *freezer) +{ + return css_freezer(freezer->css.parent); +} + +bool cgroup_freezing(struct task_struct *task) +{ + bool ret; + + rcu_read_lock(); + ret = task_freezer(task)->state & CGROUP_FREEZING; + rcu_read_unlock(); + + return ret; +} + +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) +{ + struct freezer *freezer; + + freezer = kzalloc(sizeof(struct freezer), GFP_KERNEL); + if (!freezer) + return ERR_PTR(-ENOMEM); + + return &freezer->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 both parent's and our + * freezer->lock. + */ +static int freezer_css_online(struct cgroup_subsys_state *css) +{ + struct freezer *freezer = css_freezer(css); + struct freezer *parent = parent_freezer(freezer); + + mutex_lock(&freezer_mutex); + + freezer->state |= CGROUP_FREEZER_ONLINE; + + if (parent && (parent->state & CGROUP_FREEZING)) { + freezer->state |= CGROUP_FREEZING_PARENT | CGROUP_FROZEN; + atomic_inc(&system_freezing_cnt); + } + + mutex_unlock(&freezer_mutex); + return 0; +} + +/** + * freezer_css_offline - initiate destruction of a freezer css + * @css: css being destroyed + * + * @css is going away. Mark it dead and decrement system_freezing_count if + * it was holding one. + */ +static void freezer_css_offline(struct cgroup_subsys_state *css) +{ + struct freezer *freezer = css_freezer(css); + + mutex_lock(&freezer_mutex); + + if (freezer->state & CGROUP_FREEZING) + atomic_dec(&system_freezing_cnt); + + freezer->state = 0; + + mutex_unlock(&freezer_mutex); +} + +static void freezer_css_free(struct cgroup_subsys_state *css) +{ + kfree(css_freezer(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) +{ + struct task_struct *task; + struct cgroup_subsys_state *new_css; + + mutex_lock(&freezer_mutex); + + /* + * Make the new tasks conform to the current state of @new_css. + * For simplicity, when migrating any task to a FROZEN cgroup, we + * revert it to FREEZING and let update_if_frozen() determine the + * correct state later. + * + * Tasks in @tset are on @new_css but may not conform to its + * current state before executing the following - !frozen tasks may + * be visible in a FROZEN cgroup and frozen tasks in a THAWED one. + */ + cgroup_taskset_for_each(task, new_css, tset) { + struct freezer *freezer = css_freezer(new_css); + + if (!(freezer->state & CGROUP_FREEZING)) { + __thaw_task(task); + } else { + freeze_task(task); + /* clear FROZEN and propagate upwards */ + while (freezer && (freezer->state & CGROUP_FROZEN)) { + freezer->state &= ~CGROUP_FROZEN; + freezer = parent_freezer(freezer); + } + } + } + + mutex_unlock(&freezer_mutex); +} + +/** + * 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) +{ + struct freezer *freezer; + + /* + * The root cgroup is non-freezable, so we can skip locking the + * freezer. This is safe regardless of race with task migration. + * If we didn't race or won, skipping is obviously the right thing + * to do. If we lost and root is the new cgroup, noop is still the + * right thing to do. + */ + if (task_css_is_root(task, freezer_cgrp_id)) + return; + + mutex_lock(&freezer_mutex); + rcu_read_lock(); + + freezer = task_freezer(task); + if (freezer->state & CGROUP_FREEZING) + freeze_task(task); + + rcu_read_unlock(); + mutex_unlock(&freezer_mutex); +} + +/** + * 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) +{ + struct freezer *freezer = css_freezer(css); + struct cgroup_subsys_state *pos; + struct css_task_iter it; + struct task_struct *task; + + lockdep_assert_held(&freezer_mutex); + + if (!(freezer->state & CGROUP_FREEZING) || + (freezer->state & CGROUP_FROZEN)) + return; + + /* are all (live) children frozen? */ + rcu_read_lock(); + css_for_each_child(pos, css) { + struct freezer *child = css_freezer(pos); + + if ((child->state & CGROUP_FREEZER_ONLINE) && + !(child->state & CGROUP_FROZEN)) { + rcu_read_unlock(); + return; + } + } + rcu_read_unlock(); + + /* are all tasks frozen? */ + css_task_iter_start(css, 0, &it); + + while ((task = css_task_iter_next(&it))) { + if (freezing(task)) { + /* + * freezer_should_skip() indicates that the task + * should be skipped when determining freezing + * completion. Consider it frozen in addition to + * the usual frozen condition. + */ + if (!frozen(task) && !freezer_should_skip(task)) + goto out_iter_end; + } + } + + freezer->state |= CGROUP_FROZEN; +out_iter_end: + css_task_iter_end(&it); +} + +static int freezer_read(struct seq_file *m, void *v) +{ + struct cgroup_subsys_state *css = seq_css(m), *pos; + + mutex_lock(&freezer_mutex); + rcu_read_lock(); + + /* update states bottom-up */ + css_for_each_descendant_post(pos, css) { + if (!css_tryget_online(pos)) + continue; + rcu_read_unlock(); + + update_if_frozen(pos); + + rcu_read_lock(); + css_put(pos); + } + + rcu_read_unlock(); + mutex_unlock(&freezer_mutex); + + seq_puts(m, freezer_state_strs(css_freezer(css)->state)); + seq_putc(m, '\n'); + return 0; +} + +static void freeze_cgroup(struct freezer *freezer) +{ + struct css_task_iter it; + struct task_struct *task; + + css_task_iter_start(&freezer->css, 0, &it); + while ((task = css_task_iter_next(&it))) + freeze_task(task); + css_task_iter_end(&it); +} + +static void unfreeze_cgroup(struct freezer *freezer) +{ + struct css_task_iter it; + struct task_struct *task; + + css_task_iter_start(&freezer->css, 0, &it); + while ((task = css_task_iter_next(&it))) + __thaw_task(task); + css_task_iter_end(&it); +} + +/** + * 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) +{ + /* also synchronizes against task migration, see freezer_attach() */ + lockdep_assert_held(&freezer_mutex); + + if (!(freezer->state & CGROUP_FREEZER_ONLINE)) + return; + + if (freeze) { + if (!(freezer->state & CGROUP_FREEZING)) + atomic_inc(&system_freezing_cnt); + freezer->state |= state; + freeze_cgroup(freezer); + } else { + bool was_freezing = freezer->state & CGROUP_FREEZING; + + freezer->state &= ~state; + + if (!(freezer->state & CGROUP_FREEZING)) { + if (was_freezing) + atomic_dec(&system_freezing_cnt); + freezer->state &= ~CGROUP_FROZEN; + unfreeze_cgroup(freezer); + } + } +} + +/** + * 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) +{ + struct cgroup_subsys_state *pos; + + /* + * Update all its descendants in pre-order traversal. Each + * descendant will try to inherit its parent's FREEZING state as + * CGROUP_FREEZING_PARENT. + */ + mutex_lock(&freezer_mutex); + rcu_read_lock(); + css_for_each_descendant_pre(pos, &freezer->css) { + struct freezer *pos_f = css_freezer(pos); + struct freezer *parent = parent_freezer(pos_f); + + if (!css_tryget_online(pos)) + continue; + rcu_read_unlock(); + + if (pos_f == freezer) + freezer_apply_state(pos_f, freeze, + CGROUP_FREEZING_SELF); + else + freezer_apply_state(pos_f, + parent->state & CGROUP_FREEZING, + CGROUP_FREEZING_PARENT); + + rcu_read_lock(); + css_put(pos); + } + rcu_read_unlock(); + mutex_unlock(&freezer_mutex); +} + +static ssize_t freezer_write(struct kernfs_open_file *of, + char *buf, size_t nbytes, loff_t off) +{ + bool freeze; + + buf = strstrip(buf); + + if (strcmp(buf, freezer_state_strs(0)) == 0) + freeze = false; + else if (strcmp(buf, freezer_state_strs(CGROUP_FROZEN)) == 0) + freeze = true; + else + return -EINVAL; + + freezer_change_state(css_freezer(of_css(of)), freeze); + return nbytes; +} + +static u64 freezer_self_freezing_read(struct cgroup_subsys_state *css, + struct cftype *cft) +{ + struct freezer *freezer = css_freezer(css); + + return (bool)(freezer->state & CGROUP_FREEZING_SELF); +} + +static u64 freezer_parent_freezing_read(struct cgroup_subsys_state *css, + struct cftype *cft) +{ + struct freezer *freezer = css_freezer(css); + + return (bool)(freezer->state & CGROUP_FREEZING_PARENT); +} + +static struct cftype files[] = { + { + .name = "state", + .flags = CFTYPE_NOT_ON_ROOT, + .seq_show = freezer_read, + .write = freezer_write, + }, + { + .name = "self_freezing", + .flags = CFTYPE_NOT_ON_ROOT, + .read_u64 = freezer_self_freezing_read, + }, + { + .name = "parent_freezing", + .flags = CFTYPE_NOT_ON_ROOT, + .read_u64 = freezer_parent_freezing_read, + }, + { } /* terminate */ +}; + +struct cgroup_subsys freezer_cgrp_subsys = { + .css_alloc = freezer_css_alloc, + .css_online = freezer_css_online, + .css_offline = freezer_css_offline, + .css_free = freezer_css_free, + .attach = freezer_attach, + .fork = freezer_fork, + .legacy_cftypes = files, +}; |