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481 lines
12 KiB
481 lines
12 KiB
/* |
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* cgroup_freezer.c - control group freezer subsystem |
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* |
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* Copyright IBM Corporation, 2007 |
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* |
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* Author : Cedric Le Goater <[email protected]> |
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* |
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* This program is free software; you can redistribute it and/or modify it |
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* under the terms of version 2.1 of the GNU Lesser General Public License |
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* as published by the Free Software Foundation. |
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* |
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* This program is distributed in the hope that it would be useful, but |
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* WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. |
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*/ |
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#include <linux/export.h> |
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#include <linux/slab.h> |
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#include <linux/cgroup.h> |
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#include <linux/fs.h> |
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#include <linux/uaccess.h> |
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#include <linux/freezer.h> |
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#include <linux/seq_file.h> |
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#include <linux/mutex.h> |
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/* |
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* A cgroup is freezing if any FREEZING flags are set. FREEZING_SELF is |
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* set if "FROZEN" is written to freezer.state cgroupfs file, and cleared |
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* for "THAWED". FREEZING_PARENT is set if the parent freezer is FREEZING |
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* for whatever reason. IOW, a cgroup has FREEZING_PARENT set if one of |
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* its ancestors has FREEZING_SELF set. |
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*/ |
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enum freezer_state_flags { |
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CGROUP_FREEZER_ONLINE = (1 << 0), /* freezer is fully online */ |
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CGROUP_FREEZING_SELF = (1 << 1), /* this freezer is freezing */ |
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CGROUP_FREEZING_PARENT = (1 << 2), /* the parent freezer is freezing */ |
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CGROUP_FROZEN = (1 << 3), /* this and its descendants frozen */ |
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/* mask for all FREEZING flags */ |
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CGROUP_FREEZING = CGROUP_FREEZING_SELF | CGROUP_FREEZING_PARENT, |
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}; |
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struct freezer { |
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struct cgroup_subsys_state css; |
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unsigned int state; |
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}; |
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static DEFINE_MUTEX(freezer_mutex); |
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static inline struct freezer *css_freezer(struct cgroup_subsys_state *css) |
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{ |
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return css ? container_of(css, struct freezer, css) : NULL; |
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} |
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static inline struct freezer *task_freezer(struct task_struct *task) |
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{ |
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return css_freezer(task_css(task, freezer_cgrp_id)); |
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} |
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static struct freezer *parent_freezer(struct freezer *freezer) |
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{ |
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return css_freezer(freezer->css.parent); |
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} |
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bool cgroup_freezing(struct task_struct *task) |
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{ |
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bool ret; |
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rcu_read_lock(); |
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ret = task_freezer(task)->state & CGROUP_FREEZING; |
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rcu_read_unlock(); |
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return ret; |
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} |
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static const char *freezer_state_strs(unsigned int state) |
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{ |
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if (state & CGROUP_FROZEN) |
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return "FROZEN"; |
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if (state & CGROUP_FREEZING) |
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return "FREEZING"; |
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return "THAWED"; |
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}; |
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static struct cgroup_subsys_state * |
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freezer_css_alloc(struct cgroup_subsys_state *parent_css) |
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{ |
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struct freezer *freezer; |
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freezer = kzalloc(sizeof(struct freezer), GFP_KERNEL); |
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if (!freezer) |
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return ERR_PTR(-ENOMEM); |
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return &freezer->css; |
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} |
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/** |
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* freezer_css_online - commit creation of a freezer css |
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* @css: css being created |
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* |
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* We're committing to creation of @css. Mark it online and inherit |
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* parent's freezing state while holding both parent's and our |
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* freezer->lock. |
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*/ |
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static int freezer_css_online(struct cgroup_subsys_state *css) |
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{ |
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struct freezer *freezer = css_freezer(css); |
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struct freezer *parent = parent_freezer(freezer); |
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mutex_lock(&freezer_mutex); |
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freezer->state |= CGROUP_FREEZER_ONLINE; |
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if (parent && (parent->state & CGROUP_FREEZING)) { |
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freezer->state |= CGROUP_FREEZING_PARENT | CGROUP_FROZEN; |
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atomic_inc(&system_freezing_cnt); |
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} |
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mutex_unlock(&freezer_mutex); |
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return 0; |
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} |
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/** |
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* freezer_css_offline - initiate destruction of a freezer css |
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* @css: css being destroyed |
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* |
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* @css is going away. Mark it dead and decrement system_freezing_count if |
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* it was holding one. |
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*/ |
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static void freezer_css_offline(struct cgroup_subsys_state *css) |
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{ |
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struct freezer *freezer = css_freezer(css); |
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mutex_lock(&freezer_mutex); |
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if (freezer->state & CGROUP_FREEZING) |
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atomic_dec(&system_freezing_cnt); |
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freezer->state = 0; |
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mutex_unlock(&freezer_mutex); |
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} |
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static void freezer_css_free(struct cgroup_subsys_state *css) |
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{ |
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kfree(css_freezer(css)); |
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} |
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/* |
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* Tasks can be migrated into a different freezer anytime regardless of its |
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* current state. freezer_attach() is responsible for making new tasks |
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* conform to the current state. |
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* |
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* Freezer state changes and task migration are synchronized via |
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* @freezer->lock. freezer_attach() makes the new tasks conform to the |
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* current state and all following state changes can see the new tasks. |
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*/ |
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static void freezer_attach(struct cgroup_taskset *tset) |
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{ |
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struct task_struct *task; |
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struct cgroup_subsys_state *new_css; |
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mutex_lock(&freezer_mutex); |
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/* |
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* Make the new tasks conform to the current state of @new_css. |
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* For simplicity, when migrating any task to a FROZEN cgroup, we |
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* revert it to FREEZING and let update_if_frozen() determine the |
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* correct state later. |
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* |
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* Tasks in @tset are on @new_css but may not conform to its |
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* current state before executing the following - !frozen tasks may |
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* be visible in a FROZEN cgroup and frozen tasks in a THAWED one. |
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*/ |
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cgroup_taskset_for_each(task, new_css, tset) { |
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struct freezer *freezer = css_freezer(new_css); |
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if (!(freezer->state & CGROUP_FREEZING)) { |
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__thaw_task(task); |
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} else { |
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freeze_task(task); |
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/* clear FROZEN and propagate upwards */ |
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while (freezer && (freezer->state & CGROUP_FROZEN)) { |
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freezer->state &= ~CGROUP_FROZEN; |
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freezer = parent_freezer(freezer); |
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} |
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} |
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} |
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mutex_unlock(&freezer_mutex); |
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} |
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/** |
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* freezer_fork - cgroup post fork callback |
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* @task: a task which has just been forked |
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* |
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* @task has just been created and should conform to the current state of |
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* the cgroup_freezer it belongs to. This function may race against |
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* freezer_attach(). Losing to freezer_attach() means that we don't have |
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* to do anything as freezer_attach() will put @task into the appropriate |
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* state. |
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*/ |
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static void freezer_fork(struct task_struct *task) |
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{ |
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struct freezer *freezer; |
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/* |
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* The root cgroup is non-freezable, so we can skip locking the |
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* freezer. This is safe regardless of race with task migration. |
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* If we didn't race or won, skipping is obviously the right thing |
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* to do. If we lost and root is the new cgroup, noop is still the |
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* right thing to do. |
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*/ |
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if (task_css_is_root(task, freezer_cgrp_id)) |
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return; |
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mutex_lock(&freezer_mutex); |
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rcu_read_lock(); |
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freezer = task_freezer(task); |
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if (freezer->state & CGROUP_FREEZING) |
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freeze_task(task); |
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rcu_read_unlock(); |
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mutex_unlock(&freezer_mutex); |
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} |
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/** |
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* update_if_frozen - update whether a cgroup finished freezing |
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* @css: css of interest |
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* |
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* Once FREEZING is initiated, transition to FROZEN is lazily updated by |
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* calling this function. If the current state is FREEZING but not FROZEN, |
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* this function checks whether all tasks of this cgroup and the descendant |
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* cgroups finished freezing and, if so, sets FROZEN. |
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* |
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* The caller is responsible for grabbing RCU read lock and calling |
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* update_if_frozen() on all descendants prior to invoking this function. |
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* |
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* Task states and freezer state might disagree while tasks are being |
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* migrated into or out of @css, so we can't verify task states against |
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* @freezer state here. See freezer_attach() for details. |
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*/ |
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static void update_if_frozen(struct cgroup_subsys_state *css) |
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{ |
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struct freezer *freezer = css_freezer(css); |
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struct cgroup_subsys_state *pos; |
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struct css_task_iter it; |
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struct task_struct *task; |
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lockdep_assert_held(&freezer_mutex); |
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if (!(freezer->state & CGROUP_FREEZING) || |
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(freezer->state & CGROUP_FROZEN)) |
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return; |
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/* are all (live) children frozen? */ |
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rcu_read_lock(); |
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css_for_each_child(pos, css) { |
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struct freezer *child = css_freezer(pos); |
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if ((child->state & CGROUP_FREEZER_ONLINE) && |
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!(child->state & CGROUP_FROZEN)) { |
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rcu_read_unlock(); |
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return; |
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} |
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} |
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rcu_read_unlock(); |
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/* are all tasks frozen? */ |
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css_task_iter_start(css, &it); |
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while ((task = css_task_iter_next(&it))) { |
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if (freezing(task)) { |
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/* |
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* freezer_should_skip() indicates that the task |
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* should be skipped when determining freezing |
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* completion. Consider it frozen in addition to |
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* the usual frozen condition. |
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*/ |
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if (!frozen(task) && !freezer_should_skip(task)) |
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goto out_iter_end; |
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} |
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} |
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freezer->state |= CGROUP_FROZEN; |
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out_iter_end: |
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css_task_iter_end(&it); |
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} |
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static int freezer_read(struct seq_file *m, void *v) |
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{ |
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struct cgroup_subsys_state *css = seq_css(m), *pos; |
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mutex_lock(&freezer_mutex); |
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rcu_read_lock(); |
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/* update states bottom-up */ |
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css_for_each_descendant_post(pos, css) { |
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if (!css_tryget_online(pos)) |
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continue; |
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rcu_read_unlock(); |
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update_if_frozen(pos); |
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rcu_read_lock(); |
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css_put(pos); |
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} |
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rcu_read_unlock(); |
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mutex_unlock(&freezer_mutex); |
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seq_puts(m, freezer_state_strs(css_freezer(css)->state)); |
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seq_putc(m, '\n'); |
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return 0; |
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} |
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static void freeze_cgroup(struct freezer *freezer) |
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{ |
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struct css_task_iter it; |
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struct task_struct *task; |
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css_task_iter_start(&freezer->css, &it); |
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while ((task = css_task_iter_next(&it))) |
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freeze_task(task); |
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css_task_iter_end(&it); |
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} |
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static void unfreeze_cgroup(struct freezer *freezer) |
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{ |
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struct css_task_iter it; |
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struct task_struct *task; |
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css_task_iter_start(&freezer->css, &it); |
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while ((task = css_task_iter_next(&it))) |
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__thaw_task(task); |
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css_task_iter_end(&it); |
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} |
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/** |
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* freezer_apply_state - apply state change to a single cgroup_freezer |
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* @freezer: freezer to apply state change to |
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* @freeze: whether to freeze or unfreeze |
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* @state: CGROUP_FREEZING_* flag to set or clear |
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* |
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* Set or clear @state on @cgroup according to @freeze, and perform |
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* freezing or thawing as necessary. |
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*/ |
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static void freezer_apply_state(struct freezer *freezer, bool freeze, |
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unsigned int state) |
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{ |
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/* also synchronizes against task migration, see freezer_attach() */ |
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lockdep_assert_held(&freezer_mutex); |
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if (!(freezer->state & CGROUP_FREEZER_ONLINE)) |
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return; |
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if (freeze) { |
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if (!(freezer->state & CGROUP_FREEZING)) |
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atomic_inc(&system_freezing_cnt); |
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freezer->state |= state; |
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freeze_cgroup(freezer); |
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} else { |
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bool was_freezing = freezer->state & CGROUP_FREEZING; |
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freezer->state &= ~state; |
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if (!(freezer->state & CGROUP_FREEZING)) { |
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if (was_freezing) |
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atomic_dec(&system_freezing_cnt); |
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freezer->state &= ~CGROUP_FROZEN; |
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unfreeze_cgroup(freezer); |
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} |
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} |
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} |
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/** |
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* freezer_change_state - change the freezing state of a cgroup_freezer |
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* @freezer: freezer of interest |
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* @freeze: whether to freeze or thaw |
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* |
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* Freeze or thaw @freezer according to @freeze. The operations are |
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* recursive - all descendants of @freezer will be affected. |
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*/ |
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static void freezer_change_state(struct freezer *freezer, bool freeze) |
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{ |
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struct cgroup_subsys_state *pos; |
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/* |
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* Update all its descendants in pre-order traversal. Each |
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* descendant will try to inherit its parent's FREEZING state as |
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* CGROUP_FREEZING_PARENT. |
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*/ |
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mutex_lock(&freezer_mutex); |
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rcu_read_lock(); |
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css_for_each_descendant_pre(pos, &freezer->css) { |
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struct freezer *pos_f = css_freezer(pos); |
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struct freezer *parent = parent_freezer(pos_f); |
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if (!css_tryget_online(pos)) |
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continue; |
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rcu_read_unlock(); |
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if (pos_f == freezer) |
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freezer_apply_state(pos_f, freeze, |
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CGROUP_FREEZING_SELF); |
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else |
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freezer_apply_state(pos_f, |
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parent->state & CGROUP_FREEZING, |
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CGROUP_FREEZING_PARENT); |
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rcu_read_lock(); |
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css_put(pos); |
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} |
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rcu_read_unlock(); |
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mutex_unlock(&freezer_mutex); |
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} |
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static ssize_t freezer_write(struct kernfs_open_file *of, |
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char *buf, size_t nbytes, loff_t off) |
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{ |
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bool freeze; |
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buf = strstrip(buf); |
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if (strcmp(buf, freezer_state_strs(0)) == 0) |
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freeze = false; |
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else if (strcmp(buf, freezer_state_strs(CGROUP_FROZEN)) == 0) |
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freeze = true; |
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else |
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return -EINVAL; |
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freezer_change_state(css_freezer(of_css(of)), freeze); |
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return nbytes; |
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} |
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static u64 freezer_self_freezing_read(struct cgroup_subsys_state *css, |
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struct cftype *cft) |
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{ |
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struct freezer *freezer = css_freezer(css); |
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return (bool)(freezer->state & CGROUP_FREEZING_SELF); |
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} |
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static u64 freezer_parent_freezing_read(struct cgroup_subsys_state *css, |
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struct cftype *cft) |
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{ |
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struct freezer *freezer = css_freezer(css); |
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return (bool)(freezer->state & CGROUP_FREEZING_PARENT); |
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} |
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static struct cftype files[] = { |
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{ |
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.name = "state", |
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.flags = CFTYPE_NOT_ON_ROOT, |
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.seq_show = freezer_read, |
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.write = freezer_write, |
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}, |
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{ |
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.name = "self_freezing", |
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.flags = CFTYPE_NOT_ON_ROOT, |
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.read_u64 = freezer_self_freezing_read, |
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}, |
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{ |
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.name = "parent_freezing", |
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.flags = CFTYPE_NOT_ON_ROOT, |
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.read_u64 = freezer_parent_freezing_read, |
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}, |
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{ } /* terminate */ |
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}; |
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struct cgroup_subsys freezer_cgrp_subsys = { |
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.css_alloc = freezer_css_alloc, |
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.css_online = freezer_css_online, |
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.css_offline = freezer_css_offline, |
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.css_free = freezer_css_free, |
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.attach = freezer_attach, |
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.fork = freezer_fork, |
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.legacy_cftypes = files, |
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};
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