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authorLinus Torvalds <torvalds@linux-foundation.org>2019-05-09 13:52:12 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-05-09 13:52:12 -0700
commitabde77eb5c66b2f98539c4644b54f34b7e179e6b (patch)
treecc6f6142641397e895fba9a19d0971f3827d7422 /kernel/cgroup
parent23c970608a0931b913f96f6117ea3e9e1bc06959 (diff)
parentf2b31bb598248c04721cb8485e6091a9feb045ac (diff)
downloadlinux-abde77eb5c66b2f98539c4644b54f34b7e179e6b.tar.bz2
Merge branch 'for-5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup updates from Tejun Heo: "This includes Roman's cgroup2 freezer implementation. It's a separate machanism from cgroup1 freezer. Instead of blocking user tasks in arbitrary uninterruptible sleeps, the new implementation extends jobctl stop - frozen tasks are trapped in jobctl stop until thawed and can be killed and ptraced. Lots of thanks to Oleg for sheperding the effort. Other than that, there are a few trivial changes" * 'for-5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: cgroup: never call do_group_exit() with task->frozen bit set kernel: cgroup: fix misuse of %x cgroup: get rid of cgroup_freezer_frozen_exit() cgroup: prevent spurious transition into non-frozen state cgroup: Remove unused cgrp variable cgroup: document cgroup v2 freezer interface cgroup: add tracing points for cgroup v2 freezer cgroup: make TRACE_CGROUP_PATH irq-safe kselftests: cgroup: add freezer controller self-tests kselftests: cgroup: don't fail on cg_kill_all() error in cg_destroy() cgroup: cgroup v2 freezer cgroup: protect cgroup->nr_(dying_)descendants by css_set_lock cgroup: implement __cgroup_task_count() helper cgroup: rename freezer.c into legacy_freezer.c cgroup: remove extra cgroup_migrate_finish() call
Diffstat (limited to 'kernel/cgroup')
-rw-r--r--kernel/cgroup/Makefile4
-rw-r--r--kernel/cgroup/cgroup-internal.h8
-rw-r--r--kernel/cgroup/cgroup-v1.c16
-rw-r--r--kernel/cgroup/cgroup.c152
-rw-r--r--kernel/cgroup/debug.c8
-rw-r--r--kernel/cgroup/freezer.c639
-rw-r--r--kernel/cgroup/legacy_freezer.c481
7 files changed, 873 insertions, 435 deletions
diff --git a/kernel/cgroup/Makefile b/kernel/cgroup/Makefile
index bfcdae896122..5d7a76bfbbb7 100644
--- a/kernel/cgroup/Makefile
+++ b/kernel/cgroup/Makefile
@@ -1,7 +1,7 @@
# SPDX-License-Identifier: GPL-2.0
-obj-y := cgroup.o rstat.o namespace.o cgroup-v1.o
+obj-y := cgroup.o rstat.o namespace.o cgroup-v1.o freezer.o
-obj-$(CONFIG_CGROUP_FREEZER) += freezer.o
+obj-$(CONFIG_CGROUP_FREEZER) += legacy_freezer.o
obj-$(CONFIG_CGROUP_PIDS) += pids.o
obj-$(CONFIG_CGROUP_RDMA) += rdma.o
obj-$(CONFIG_CPUSETS) += cpuset.o
diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h
index 30e39f3932ad..809e34a3c017 100644
--- a/kernel/cgroup/cgroup-internal.h
+++ b/kernel/cgroup/cgroup-internal.h
@@ -28,12 +28,15 @@ extern void __init enable_debug_cgroup(void);
#define TRACE_CGROUP_PATH(type, cgrp, ...) \
do { \
if (trace_cgroup_##type##_enabled()) { \
- spin_lock(&trace_cgroup_path_lock); \
+ unsigned long flags; \
+ spin_lock_irqsave(&trace_cgroup_path_lock, \
+ flags); \
cgroup_path(cgrp, trace_cgroup_path, \
TRACE_CGROUP_PATH_LEN); \
trace_cgroup_##type(cgrp, trace_cgroup_path, \
##__VA_ARGS__); \
- spin_unlock(&trace_cgroup_path_lock); \
+ spin_unlock_irqrestore(&trace_cgroup_path_lock, \
+ flags); \
} \
} while (0)
@@ -240,6 +243,7 @@ int cgroup_rmdir(struct kernfs_node *kn);
int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
struct kernfs_root *kf_root);
+int __cgroup_task_count(const struct cgroup *cgrp);
int cgroup_task_count(const struct cgroup *cgrp);
/*
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index c126b34fd4ff..68ca5de7ec27 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -342,22 +342,6 @@ static struct cgroup_pidlist *cgroup_pidlist_find_create(struct cgroup *cgrp,
return l;
}
-/**
- * cgroup_task_count - count the number of tasks in a cgroup.
- * @cgrp: the cgroup in question
- */
-int cgroup_task_count(const struct cgroup *cgrp)
-{
- int count = 0;
- struct cgrp_cset_link *link;
-
- spin_lock_irq(&css_set_lock);
- list_for_each_entry(link, &cgrp->cset_links, cset_link)
- count += link->cset->nr_tasks;
- spin_unlock_irq(&css_set_lock);
- return count;
-}
-
/*
* Load a cgroup's pidarray with either procs' tgids or tasks' pids
*/
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 3f2b4bde0f9c..327f37c9fdfa 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -593,6 +593,39 @@ static void cgroup_get_live(struct cgroup *cgrp)
css_get(&cgrp->self);
}
+/**
+ * __cgroup_task_count - count the number of tasks in a cgroup. The caller
+ * is responsible for taking the css_set_lock.
+ * @cgrp: the cgroup in question
+ */
+int __cgroup_task_count(const struct cgroup *cgrp)
+{
+ int count = 0;
+ struct cgrp_cset_link *link;
+
+ lockdep_assert_held(&css_set_lock);
+
+ list_for_each_entry(link, &cgrp->cset_links, cset_link)
+ count += link->cset->nr_tasks;
+
+ return count;
+}
+
+/**
+ * cgroup_task_count - count the number of tasks in a cgroup.
+ * @cgrp: the cgroup in question
+ */
+int cgroup_task_count(const struct cgroup *cgrp)
+{
+ int count;
+
+ spin_lock_irq(&css_set_lock);
+ count = __cgroup_task_count(cgrp);
+ spin_unlock_irq(&css_set_lock);
+
+ return count;
+}
+
struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
{
struct cgroup *cgrp = of->kn->parent->priv;
@@ -783,6 +816,8 @@ static void cgroup_update_populated(struct cgroup *cgrp, bool populated)
break;
cgroup1_check_for_release(cgrp);
+ TRACE_CGROUP_PATH(notify_populated, cgrp,
+ cgroup_is_populated(cgrp));
cgroup_file_notify(&cgrp->events_file);
child = cgrp;
@@ -2402,8 +2437,15 @@ static int cgroup_migrate_execute(struct cgroup_mgctx *mgctx)
get_css_set(to_cset);
to_cset->nr_tasks++;
css_set_move_task(task, from_cset, to_cset, true);
- put_css_set_locked(from_cset);
from_cset->nr_tasks--;
+ /*
+ * If the source or destination cgroup is frozen,
+ * the task might require to change its state.
+ */
+ cgroup_freezer_migrate_task(task, from_cset->dfl_cgrp,
+ to_cset->dfl_cgrp);
+ put_css_set_locked(from_cset);
+
}
}
spin_unlock_irq(&css_set_lock);
@@ -2602,7 +2644,7 @@ int cgroup_migrate_prepare_dst(struct cgroup_mgctx *mgctx)
dst_cset = find_css_set(src_cset, src_cset->mg_dst_cgrp);
if (!dst_cset)
- goto err;
+ return -ENOMEM;
WARN_ON_ONCE(src_cset->mg_dst_cset || dst_cset->mg_dst_cset);
@@ -2634,9 +2676,6 @@ int cgroup_migrate_prepare_dst(struct cgroup_mgctx *mgctx)
}
return 0;
-err:
- cgroup_migrate_finish(mgctx);
- return -ENOMEM;
}
/**
@@ -3447,8 +3486,11 @@ static ssize_t cgroup_max_depth_write(struct kernfs_open_file *of,
static int cgroup_events_show(struct seq_file *seq, void *v)
{
- seq_printf(seq, "populated %d\n",
- cgroup_is_populated(seq_css(seq)->cgroup));
+ struct cgroup *cgrp = seq_css(seq)->cgroup;
+
+ seq_printf(seq, "populated %d\n", cgroup_is_populated(cgrp));
+ seq_printf(seq, "frozen %d\n", test_bit(CGRP_FROZEN, &cgrp->flags));
+
return 0;
}
@@ -3510,6 +3552,40 @@ static int cgroup_cpu_pressure_show(struct seq_file *seq, void *v)
}
#endif
+static int cgroup_freeze_show(struct seq_file *seq, void *v)
+{
+ struct cgroup *cgrp = seq_css(seq)->cgroup;
+
+ seq_printf(seq, "%d\n", cgrp->freezer.freeze);
+
+ return 0;
+}
+
+static ssize_t cgroup_freeze_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes, loff_t off)
+{
+ struct cgroup *cgrp;
+ ssize_t ret;
+ int freeze;
+
+ ret = kstrtoint(strstrip(buf), 0, &freeze);
+ if (ret)
+ return ret;
+
+ if (freeze < 0 || freeze > 1)
+ return -ERANGE;
+
+ cgrp = cgroup_kn_lock_live(of->kn, false);
+ if (!cgrp)
+ return -ENOENT;
+
+ cgroup_freeze(cgrp, freeze);
+
+ cgroup_kn_unlock(of->kn);
+
+ return nbytes;
+}
+
static int cgroup_file_open(struct kernfs_open_file *of)
{
struct cftype *cft = of->kn->priv;
@@ -4654,6 +4730,12 @@ static struct cftype cgroup_base_files[] = {
.seq_show = cgroup_stat_show,
},
{
+ .name = "cgroup.freeze",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .seq_show = cgroup_freeze_show,
+ .write = cgroup_freeze_write,
+ },
+ {
.name = "cpu.stat",
.flags = CFTYPE_NOT_ON_ROOT,
.seq_show = cpu_stat_show,
@@ -4781,9 +4863,11 @@ static void css_release_work_fn(struct work_struct *work)
if (cgroup_on_dfl(cgrp))
cgroup_rstat_flush(cgrp);
+ spin_lock_irq(&css_set_lock);
for (tcgrp = cgroup_parent(cgrp); tcgrp;
tcgrp = cgroup_parent(tcgrp))
tcgrp->nr_dying_descendants--;
+ spin_unlock_irq(&css_set_lock);
cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
cgrp->id = -1;
@@ -5001,12 +5085,31 @@ static struct cgroup *cgroup_create(struct cgroup *parent)
if (ret)
goto out_psi_free;
+ /*
+ * New cgroup inherits effective freeze counter, and
+ * if the parent has to be frozen, the child has too.
+ */
+ cgrp->freezer.e_freeze = parent->freezer.e_freeze;
+ if (cgrp->freezer.e_freeze)
+ set_bit(CGRP_FROZEN, &cgrp->flags);
+
+ spin_lock_irq(&css_set_lock);
for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp)) {
cgrp->ancestor_ids[tcgrp->level] = tcgrp->id;
- if (tcgrp != cgrp)
+ if (tcgrp != cgrp) {
tcgrp->nr_descendants++;
+
+ /*
+ * If the new cgroup is frozen, all ancestor cgroups
+ * get a new frozen descendant, but their state can't
+ * change because of this.
+ */
+ if (cgrp->freezer.e_freeze)
+ tcgrp->freezer.nr_frozen_descendants++;
+ }
}
+ spin_unlock_irq(&css_set_lock);
if (notify_on_release(parent))
set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
@@ -5291,10 +5394,18 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
if (parent && cgroup_is_threaded(cgrp))
parent->nr_threaded_children--;
+ spin_lock_irq(&css_set_lock);
for (tcgrp = cgroup_parent(cgrp); tcgrp; tcgrp = cgroup_parent(tcgrp)) {
tcgrp->nr_descendants--;
tcgrp->nr_dying_descendants++;
+ /*
+ * If the dying cgroup is frozen, decrease frozen descendants
+ * counters of ancestor cgroups.
+ */
+ if (test_bit(CGRP_FROZEN, &cgrp->flags))
+ tcgrp->freezer.nr_frozen_descendants--;
}
+ spin_unlock_irq(&css_set_lock);
cgroup1_check_for_release(parent);
@@ -5746,6 +5857,26 @@ void cgroup_post_fork(struct task_struct *child)
cset->nr_tasks++;
css_set_move_task(child, NULL, cset, false);
}
+
+ /*
+ * If the cgroup has to be frozen, the new task has too.
+ * Let's set the JOBCTL_TRAP_FREEZE jobctl bit to get
+ * the task into the frozen state.
+ */
+ if (unlikely(cgroup_task_freeze(child))) {
+ spin_lock(&child->sighand->siglock);
+ WARN_ON_ONCE(child->frozen);
+ child->jobctl |= JOBCTL_TRAP_FREEZE;
+ spin_unlock(&child->sighand->siglock);
+
+ /*
+ * Calling cgroup_update_frozen() isn't required here,
+ * because it will be called anyway a bit later
+ * from do_freezer_trap(). So we avoid cgroup's
+ * transient switch from the frozen state and back.
+ */
+ }
+
spin_unlock_irq(&css_set_lock);
}
@@ -5794,6 +5925,11 @@ void cgroup_exit(struct task_struct *tsk)
spin_lock_irq(&css_set_lock);
css_set_move_task(tsk, cset, NULL, false);
cset->nr_tasks--;
+
+ WARN_ON_ONCE(cgroup_task_frozen(tsk));
+ if (unlikely(cgroup_task_freeze(tsk)))
+ cgroup_update_frozen(task_dfl_cgroup(tsk));
+
spin_unlock_irq(&css_set_lock);
} else {
get_css_set(cset);
diff --git a/kernel/cgroup/debug.c b/kernel/cgroup/debug.c
index 5f1b87330bee..80aa3f027ac3 100644
--- a/kernel/cgroup/debug.c
+++ b/kernel/cgroup/debug.c
@@ -64,8 +64,8 @@ static int current_css_set_read(struct seq_file *seq, void *v)
css = cset->subsys[ss->id];
if (!css)
continue;
- seq_printf(seq, "%2d: %-4s\t- %lx[%d]\n", ss->id, ss->name,
- (unsigned long)css, css->id);
+ seq_printf(seq, "%2d: %-4s\t- %p[%d]\n", ss->id, ss->name,
+ css, css->id);
}
rcu_read_unlock();
spin_unlock_irq(&css_set_lock);
@@ -224,8 +224,8 @@ static int cgroup_subsys_states_read(struct seq_file *seq, void *v)
if (css->parent)
snprintf(pbuf, sizeof(pbuf) - 1, " P=%d",
css->parent->id);
- seq_printf(seq, "%2d: %-4s\t- %lx[%d] %d%s\n", ss->id, ss->name,
- (unsigned long)css, css->id,
+ seq_printf(seq, "%2d: %-4s\t- %p[%d] %d%s\n", ss->id, ss->name,
+ css, css->id,
atomic_read(&css->online_cnt), pbuf);
}
diff --git a/kernel/cgroup/freezer.c b/kernel/cgroup/freezer.c
index 08236798d173..8cf010680678 100644
--- a/kernel/cgroup/freezer.c
+++ b/kernel/cgroup/freezer.c
@@ -1,481 +1,314 @@
-/*
- * 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>
+//SPDX-License-Identifier: GPL-2.0
#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 */
+#include <linux/sched.h>
+#include <linux/sched/task.h>
+#include <linux/sched/signal.h>
- /* mask for all FREEZING flags */
- CGROUP_FREEZING = CGROUP_FREEZING_SELF | CGROUP_FREEZING_PARENT,
-};
+#include "cgroup-internal.h"
-struct freezer {
- struct cgroup_subsys_state css;
- unsigned int state;
-};
+#include <trace/events/cgroup.h>
-static DEFINE_MUTEX(freezer_mutex);
-
-static inline struct freezer *css_freezer(struct cgroup_subsys_state *css)
+/*
+ * Propagate the cgroup frozen state upwards by the cgroup tree.
+ */
+static void cgroup_propagate_frozen(struct cgroup *cgrp, bool frozen)
{
- return css ? container_of(css, struct freezer, css) : NULL;
-}
+ int desc = 1;
-static inline struct freezer *task_freezer(struct task_struct *task)
-{
- return css_freezer(task_css(task, freezer_cgrp_id));
+ /*
+ * If the new state is frozen, some freezing ancestor cgroups may change
+ * their state too, depending on if all their descendants are frozen.
+ *
+ * Otherwise, all ancestor cgroups are forced into the non-frozen state.
+ */
+ while ((cgrp = cgroup_parent(cgrp))) {
+ if (frozen) {
+ cgrp->freezer.nr_frozen_descendants += desc;
+ if (!test_bit(CGRP_FROZEN, &cgrp->flags) &&
+ test_bit(CGRP_FREEZE, &cgrp->flags) &&
+ cgrp->freezer.nr_frozen_descendants ==
+ cgrp->nr_descendants) {
+ set_bit(CGRP_FROZEN, &cgrp->flags);
+ cgroup_file_notify(&cgrp->events_file);
+ TRACE_CGROUP_PATH(notify_frozen, cgrp, 1);
+ desc++;
+ }
+ } else {
+ cgrp->freezer.nr_frozen_descendants -= desc;
+ if (test_bit(CGRP_FROZEN, &cgrp->flags)) {
+ clear_bit(CGRP_FROZEN, &cgrp->flags);
+ cgroup_file_notify(&cgrp->events_file);
+ TRACE_CGROUP_PATH(notify_frozen, cgrp, 0);
+ desc++;
+ }
+ }
+ }
}
-static struct freezer *parent_freezer(struct freezer *freezer)
+/*
+ * Revisit the cgroup frozen state.
+ * Checks if the cgroup is really frozen and perform all state transitions.
+ */
+void cgroup_update_frozen(struct cgroup *cgrp)
{
- return css_freezer(freezer->css.parent);
-}
+ bool frozen;
-bool cgroup_freezing(struct task_struct *task)
-{
- bool ret;
+ lockdep_assert_held(&css_set_lock);
- rcu_read_lock();
- ret = task_freezer(task)->state & CGROUP_FREEZING;
- rcu_read_unlock();
+ /*
+ * If the cgroup has to be frozen (CGRP_FREEZE bit set),
+ * and all tasks are frozen and/or stopped, let's consider
+ * the cgroup frozen. Otherwise it's not frozen.
+ */
+ frozen = test_bit(CGRP_FREEZE, &cgrp->flags) &&
+ cgrp->freezer.nr_frozen_tasks == __cgroup_task_count(cgrp);
- return ret;
-}
+ if (frozen) {
+ /* Already there? */
+ if (test_bit(CGRP_FROZEN, &cgrp->flags))
+ return;
-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;
+ set_bit(CGRP_FROZEN, &cgrp->flags);
+ } else {
+ /* Already there? */
+ if (!test_bit(CGRP_FROZEN, &cgrp->flags))
+ return;
- freezer = kzalloc(sizeof(struct freezer), GFP_KERNEL);
- if (!freezer)
- return ERR_PTR(-ENOMEM);
+ clear_bit(CGRP_FROZEN, &cgrp->flags);
+ }
+ cgroup_file_notify(&cgrp->events_file);
+ TRACE_CGROUP_PATH(notify_frozen, cgrp, frozen);
- return &freezer->css;
+ /* Update the state of ancestor cgroups. */
+ cgroup_propagate_frozen(cgrp, frozen);
}
-/**
- * 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.
+/*
+ * Increment cgroup's nr_frozen_tasks.
*/
-static int freezer_css_online(struct cgroup_subsys_state *css)
+static void cgroup_inc_frozen_cnt(struct cgroup *cgrp)
{
- 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;
+ cgrp->freezer.nr_frozen_tasks++;
}
-/**
- * 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.
+/*
+ * Decrement cgroup's nr_frozen_tasks.
*/
-static void freezer_css_offline(struct cgroup_subsys_state *css)
+static void cgroup_dec_frozen_cnt(struct cgroup *cgrp)
{
- 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);
+ cgrp->freezer.nr_frozen_tasks--;
+ WARN_ON_ONCE(cgrp->freezer.nr_frozen_tasks < 0);
}
-static void freezer_css_free(struct cgroup_subsys_state *css)
+/*
+ * Enter frozen/stopped state, if not yet there. Update cgroup's counters,
+ * and revisit the state of the cgroup, if necessary.
+ */
+void cgroup_enter_frozen(void)
{
- kfree(css_freezer(css));
+ struct cgroup *cgrp;
+
+ if (current->frozen)
+ return;
+
+ spin_lock_irq(&css_set_lock);
+ current->frozen = true;
+ cgrp = task_dfl_cgroup(current);
+ cgroup_inc_frozen_cnt(cgrp);
+ cgroup_update_frozen(cgrp);
+ spin_unlock_irq(&css_set_lock);
}
/*
- * 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.
+ * Conditionally leave frozen/stopped state. Update cgroup's counters,
+ * and revisit the state of the cgroup, if necessary.
*
- * 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.
+ * If always_leave is not set, and the cgroup is freezing,
+ * we're racing with the cgroup freezing. In this case, we don't
+ * drop the frozen counter to avoid a transient switch to
+ * the unfrozen state.
*/
-static void freezer_attach(struct cgroup_taskset *tset)
+void cgroup_leave_frozen(bool always_leave)
{
- 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);
- }
- }
+ struct cgroup *cgrp;
+
+ spin_lock_irq(&css_set_lock);
+ cgrp = task_dfl_cgroup(current);
+ if (always_leave || !test_bit(CGRP_FREEZE, &cgrp->flags)) {
+ cgroup_dec_frozen_cnt(cgrp);
+ cgroup_update_frozen(cgrp);
+ WARN_ON_ONCE(!current->frozen);
+ current->frozen = false;
+ } else if (!(current->jobctl & JOBCTL_TRAP_FREEZE)) {
+ spin_lock(&current->sighand->siglock);
+ current->jobctl |= JOBCTL_TRAP_FREEZE;
+ set_thread_flag(TIF_SIGPENDING);
+ spin_unlock(&current->sighand->siglock);
}
-
- mutex_unlock(&freezer_mutex);
+ spin_unlock_irq(&css_set_lock);
}
-/**
- * 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.
+/*
+ * Freeze or unfreeze the task by setting or clearing the JOBCTL_TRAP_FREEZE
+ * jobctl bit.
*/
-static void freezer_fork(struct task_struct *task)
+static void cgroup_freeze_task(struct task_struct *task, bool freeze)
{
- struct freezer *freezer;
+ unsigned long flags;
- /*
- * 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))
+ /* If the task is about to die, don't bother with freezing it. */
+ if (!lock_task_sighand(task, &flags))
return;
- mutex_lock(&freezer_mutex);
- rcu_read_lock();
-
- freezer = task_freezer(task);
- if (freezer->state & CGROUP_FREEZING)
- freeze_task(task);
+ if (freeze) {
+ task->jobctl |= JOBCTL_TRAP_FREEZE;
+ signal_wake_up(task, false);
+ } else {
+ task->jobctl &= ~JOBCTL_TRAP_FREEZE;
+ wake_up_process(task);
+ }
- rcu_read_unlock();
- mutex_unlock(&freezer_mutex);
+ unlock_task_sighand(task, &flags);
}
-/**
- * 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.
+/*
+ * Freeze or unfreeze all tasks in the given cgroup.
*/
-static void update_if_frozen(struct cgroup_subsys_state *css)
+static void cgroup_do_freeze(struct cgroup *cgrp, bool freeze)
{
- 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;
+ lockdep_assert_held(&cgroup_mutex);
- /* 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();
+ spin_lock_irq(&css_set_lock);
+ if (freeze)
+ set_bit(CGRP_FREEZE, &cgrp->flags);
+ else
+ clear_bit(CGRP_FREEZE, &cgrp->flags);
+ spin_unlock_irq(&css_set_lock);
- /* are all tasks frozen? */
- css_task_iter_start(css, 0, &it);
+ if (freeze)
+ TRACE_CGROUP_PATH(freeze, cgrp);
+ else
+ TRACE_CGROUP_PATH(unfreeze, cgrp);
+ css_task_iter_start(&cgrp->self, 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))
+ /*
+ * Ignore kernel threads here. Freezing cgroups containing
+ * kthreads isn't supported.
+ */
+ if (task->flags & PF_KTHREAD)
continue;
- rcu_read_unlock();
-
- update_if_frozen(pos);
-
- rcu_read_lock();
- css_put(pos);
+ cgroup_freeze_task(task, freeze);
}
-
- 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);
+ /*
+ * Cgroup state should be revisited here to cover empty leaf cgroups
+ * and cgroups which descendants are already in the desired state.
+ */
+ spin_lock_irq(&css_set_lock);
+ if (cgrp->nr_descendants == cgrp->freezer.nr_frozen_descendants)
+ cgroup_update_frozen(cgrp);
+ spin_unlock_irq(&css_set_lock);
}
-/**
- * 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.
+/*
+ * Adjust the task state (freeze or unfreeze) and revisit the state of
+ * source and destination cgroups.
*/
-static void freezer_apply_state(struct freezer *freezer, bool freeze,
- unsigned int state)
+void cgroup_freezer_migrate_task(struct task_struct *task,
+ struct cgroup *src, struct cgroup *dst)
{
- /* also synchronizes against task migration, see freezer_attach() */
- lockdep_assert_held(&freezer_mutex);
+ lockdep_assert_held(&css_set_lock);
- if (!(freezer->state & CGROUP_FREEZER_ONLINE))
+ /*
+ * Kernel threads are not supposed to be frozen at all.
+ */
+ if (task->flags & PF_KTHREAD)
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);
- }
+ /*
+ * Adjust counters of freezing and frozen tasks.
+ * Note, that if the task is frozen, but the destination cgroup is not
+ * frozen, we bump both counters to keep them balanced.
+ */
+ if (task->frozen) {
+ cgroup_inc_frozen_cnt(dst);
+ cgroup_dec_frozen_cnt(src);
}
-}
-
-/**
- * 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;
+ cgroup_update_frozen(dst);
+ cgroup_update_frozen(src);
/*
- * Update all its descendants in pre-order traversal. Each
- * descendant will try to inherit its parent's FREEZING state as
- * CGROUP_FREEZING_PARENT.
+ * Force the task to the desired state.
*/
- 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);
+ cgroup_freeze_task(task, test_bit(CGRP_FREEZE, &dst->flags));
}
-static ssize_t freezer_write(struct kernfs_open_file *of,
- char *buf, size_t nbytes, loff_t off)
+void cgroup_freeze(struct cgroup *cgrp, bool freeze)
{
- bool freeze;
+ struct cgroup_subsys_state *css;
+ struct cgroup *dsct;
+ bool applied = false;
- buf = strstrip(buf);
+ lockdep_assert_held(&cgroup_mutex);
- 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;
+ /*
+ * Nothing changed? Just exit.
+ */
+ if (cgrp->freezer.freeze == freeze)
+ return;
- freezer_change_state(css_freezer(of_css(of)), freeze);
- return nbytes;
-}
+ cgrp->freezer.freeze = freeze;
-static u64 freezer_self_freezing_read(struct cgroup_subsys_state *css,
- struct cftype *cft)
-{
- struct freezer *freezer = css_freezer(css);
+ /*
+ * Propagate changes downwards the cgroup tree.
+ */
+ css_for_each_descendant_pre(css, &cgrp->self) {
+ dsct = css->cgroup;
- return (bool)(freezer->state & CGROUP_FREEZING_SELF);
-}
+ if (cgroup_is_dead(dsct))
+ continue;
-static u64 freezer_parent_freezing_read(struct cgroup_subsys_state *css,
- struct cftype *cft)
-{
- struct freezer *freezer = css_freezer(css);
+ if (freeze) {
+ dsct->freezer.e_freeze++;
+ /*
+ * Already frozen because of ancestor's settings?
+ */
+ if (dsct->freezer.e_freeze > 1)
+ continue;
+ } else {
+ dsct->freezer.e_freeze--;
+ /*
+ * Still frozen because of ancestor's settings?
+ */
+ if (dsct->freezer.e_freeze > 0)
+ continue;
- return (bool)(freezer->state & CGROUP_FREEZING_PARENT);
-}
+ WARN_ON_ONCE(dsct->freezer.e_freeze < 0);
+ }
+
+ /*
+ * Do change actual state: freeze or unfreeze.
+ */
+ cgroup_do_freeze(dsct, freeze);
+ applied = true;
+ }
-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,
-};
+ /*
+ * Even if the actual state hasn't changed, let's notify a user.
+ * The state can be enforced by an ancestor cgroup: the cgroup
+ * can already be in the desired state or it can be locked in the
+ * opposite state, so that the transition will never happen.
+ * In both cases it's better to notify a user, that there is
+ * nothing to wait for.
+ */
+ if (!applied) {
+ TRACE_CGROUP_PATH(notify_frozen, cgrp,
+ test_bit(CGRP_FROZEN, &cgrp->flags));
+ cgroup_file_notify(&cgrp->events_file);
+ }
+}
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,
+};