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
diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 20f92c1..88e7460 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -864,6 +864,8 @@
populated
1 if the cgroup or its descendants contains any live
processes; otherwise, 0.
+ frozen
+ 1 if the cgroup is frozen; otherwise, 0.
cgroup.max.descendants
A read-write single value files. The default is "max".
@@ -897,6 +899,31 @@
A dying cgroup can consume system resources not exceeding
limits, which were active at the moment of cgroup deletion.
+ cgroup.freeze
+ A read-write single value file which exists on non-root cgroups.
+ Allowed values are "0" and "1". The default is "0".
+
+ Writing "1" to the file causes freezing of the cgroup and all
+ descendant cgroups. This means that all belonging processes will
+ be stopped and will not run until the cgroup will be explicitly
+ unfrozen. Freezing of the cgroup may take some time; when this action
+ is completed, the "frozen" value in the cgroup.events control file
+ will be updated to "1" and the corresponding notification will be
+ issued.
+
+ A cgroup can be frozen either by its own settings, or by settings
+ of any ancestor cgroups. If any of ancestor cgroups is frozen, the
+ cgroup will remain frozen.
+
+ Processes in the frozen cgroup can be killed by a fatal signal.
+ They also can enter and leave a frozen cgroup: either by an explicit
+ move by a user, or if freezing of the cgroup races with fork().
+ If a process is moved to a frozen cgroup, it stops. If a process is
+ moved out of a frozen cgroup, it becomes running.
+
+ Frozen status of a cgroup doesn't affect any cgroup tree operations:
+ it's possible to delete a frozen (and empty) cgroup, as well as
+ create new sub-cgroups.
Controllers
===========
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 1c70803..77258d2 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -65,6 +65,12 @@
* specified at mount time and thus is implemented here.
*/
CGRP_CPUSET_CLONE_CHILDREN,
+
+ /* Control group has to be frozen. */
+ CGRP_FREEZE,
+
+ /* Cgroup is frozen. */
+ CGRP_FROZEN,
};
/* cgroup_root->flags */
@@ -317,6 +323,25 @@
struct cgroup *updated_next; /* NULL iff not on the list */
};
+struct cgroup_freezer_state {
+ /* Should the cgroup and its descendants be frozen. */
+ bool freeze;
+
+ /* Should the cgroup actually be frozen? */
+ int e_freeze;
+
+ /* Fields below are protected by css_set_lock */
+
+ /* Number of frozen descendant cgroups */
+ int nr_frozen_descendants;
+
+ /*
+ * Number of tasks, which are counted as frozen:
+ * frozen, SIGSTOPped, and PTRACEd.
+ */
+ int nr_frozen_tasks;
+};
+
struct cgroup {
/* self css with NULL ->ss, points back to this cgroup */
struct cgroup_subsys_state self;
@@ -349,6 +374,11 @@
* Dying cgroups are cgroups which were deleted by a user,
* but are still existing because someone else is holding a reference.
* max_descendants is a maximum allowed number of descent cgroups.
+ *
+ * nr_descendants and nr_dying_descendants are protected
+ * by cgroup_mutex and css_set_lock. It's fine to read them holding
+ * any of cgroup_mutex and css_set_lock; for writing both locks
+ * should be held.
*/
int nr_descendants;
int nr_dying_descendants;
@@ -448,6 +478,9 @@
/* If there is block congestion on this cgroup. */
atomic_t congestion_count;
+ /* Used to store internal freezer state */
+ struct cgroup_freezer_state freezer;
+
/* ids of the ancestors at each level including self */
int ancestor_ids[];
};
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 81f58b4..c0077ad 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -881,4 +881,47 @@
free_cgroup_ns(ns);
}
+#ifdef CONFIG_CGROUPS
+
+void cgroup_enter_frozen(void);
+void cgroup_leave_frozen(bool always_leave);
+void cgroup_update_frozen(struct cgroup *cgrp);
+void cgroup_freeze(struct cgroup *cgrp, bool freeze);
+void cgroup_freezer_migrate_task(struct task_struct *task, struct cgroup *src,
+ struct cgroup *dst);
+
+static inline bool cgroup_task_freeze(struct task_struct *task)
+{
+ bool ret;
+
+ if (task->flags & PF_KTHREAD)
+ return false;
+
+ rcu_read_lock();
+ ret = test_bit(CGRP_FREEZE, &task_dfl_cgroup(task)->flags);
+ rcu_read_unlock();
+
+ return ret;
+}
+
+static inline bool cgroup_task_frozen(struct task_struct *task)
+{
+ return task->frozen;
+}
+
+#else /* !CONFIG_CGROUPS */
+
+static inline void cgroup_enter_frozen(void) { }
+static inline void cgroup_leave_frozen(bool always_leave) { }
+static inline bool cgroup_task_freeze(struct task_struct *task)
+{
+ return false;
+}
+static inline bool cgroup_task_frozen(struct task_struct *task)
+{
+ return false;
+}
+
+#endif /* !CONFIG_CGROUPS */
+
#endif /* _LINUX_CGROUP_H */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 50606a6..a2cd1585 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -726,6 +726,8 @@
#ifdef CONFIG_CGROUPS
/* disallow userland-initiated cgroup migration */
unsigned no_cgroup_migration:1;
+ /* task is frozen/stopped (used by the cgroup freezer) */
+ unsigned frozen:1;
#endif
#ifdef CONFIG_BLK_CGROUP
/* to be used once the psi infrastructure lands upstream. */
diff --git a/include/linux/sched/jobctl.h b/include/linux/sched/jobctl.h
index 98228bd..fa067de 100644
--- a/include/linux/sched/jobctl.h
+++ b/include/linux/sched/jobctl.h
@@ -18,6 +18,7 @@
#define JOBCTL_TRAP_NOTIFY_BIT 20 /* trap for NOTIFY */
#define JOBCTL_TRAPPING_BIT 21 /* switching to TRACED */
#define JOBCTL_LISTENING_BIT 22 /* ptracer is listening for events */
+#define JOBCTL_TRAP_FREEZE_BIT 23 /* trap for cgroup freezer */
#define JOBCTL_STOP_DEQUEUED (1UL << JOBCTL_STOP_DEQUEUED_BIT)
#define JOBCTL_STOP_PENDING (1UL << JOBCTL_STOP_PENDING_BIT)
@@ -26,6 +27,7 @@
#define JOBCTL_TRAP_NOTIFY (1UL << JOBCTL_TRAP_NOTIFY_BIT)
#define JOBCTL_TRAPPING (1UL << JOBCTL_TRAPPING_BIT)
#define JOBCTL_LISTENING (1UL << JOBCTL_LISTENING_BIT)
+#define JOBCTL_TRAP_FREEZE (1UL << JOBCTL_TRAP_FREEZE_BIT)
#define JOBCTL_TRAP_MASK (JOBCTL_TRAP_STOP | JOBCTL_TRAP_NOTIFY)
#define JOBCTL_PENDING_MASK (JOBCTL_STOP_PENDING | JOBCTL_TRAP_MASK)
diff --git a/include/trace/events/cgroup.h b/include/trace/events/cgroup.h
index a401ff5..a566cc5 100644
--- a/include/trace/events/cgroup.h
+++ b/include/trace/events/cgroup.h
@@ -103,6 +103,20 @@
TP_ARGS(cgrp, path)
);
+DEFINE_EVENT(cgroup, cgroup_freeze,
+
+ TP_PROTO(struct cgroup *cgrp, const char *path),
+
+ TP_ARGS(cgrp, path)
+);
+
+DEFINE_EVENT(cgroup, cgroup_unfreeze,
+
+ TP_PROTO(struct cgroup *cgrp, const char *path),
+
+ TP_ARGS(cgrp, path)
+);
+
DECLARE_EVENT_CLASS(cgroup_migrate,
TP_PROTO(struct cgroup *dst_cgrp, const char *path,
@@ -149,6 +163,47 @@
TP_ARGS(dst_cgrp, path, task, threadgroup)
);
+DECLARE_EVENT_CLASS(cgroup_event,
+
+ TP_PROTO(struct cgroup *cgrp, const char *path, int val),
+
+ TP_ARGS(cgrp, path, val),
+
+ TP_STRUCT__entry(
+ __field( int, root )
+ __field( int, id )
+ __field( int, level )
+ __string( path, path )
+ __field( int, val )
+ ),
+
+ TP_fast_assign(
+ __entry->root = cgrp->root->hierarchy_id;
+ __entry->id = cgrp->id;
+ __entry->level = cgrp->level;
+ __assign_str(path, path);
+ __entry->val = val;
+ ),
+
+ TP_printk("root=%d id=%d level=%d path=%s val=%d",
+ __entry->root, __entry->id, __entry->level, __get_str(path),
+ __entry->val)
+);
+
+DEFINE_EVENT(cgroup_event, cgroup_notify_populated,
+
+ TP_PROTO(struct cgroup *cgrp, const char *path, int val),
+
+ TP_ARGS(cgrp, path, val)
+);
+
+DEFINE_EVENT(cgroup_event, cgroup_notify_frozen,
+
+ TP_PROTO(struct cgroup *cgrp, const char *path, int val),
+
+ TP_ARGS(cgrp, path, val)
+);
+
#endif /* _TRACE_CGROUP_H */
/* This part must be outside protection */
diff --git a/kernel/cgroup/Makefile b/kernel/cgroup/Makefile
index bfcdae8..5d7a76b 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 30e39f3..809e34a3 100644
--- a/kernel/cgroup/cgroup-internal.h
+++ b/kernel/cgroup/cgroup-internal.h
@@ -28,12 +28,15 @@
#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_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 c126b34..68ca5de 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -342,22 +342,6 @@
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 3f2b4bd..327f37c 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -593,6 +593,39 @@
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 @@
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 @@
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 @@
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 @@
}
return 0;
-err:
- cgroup_migrate_finish(mgctx);
- return -ENOMEM;
}
/**
@@ -3447,8 +3486,11 @@
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 @@
}
#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 @@
.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 @@
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 @@
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 @@
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 @@
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 @@
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 5f1b873..80aa3f0 100644
--- a/kernel/cgroup/debug.c
+++ b/kernel/cgroup/debug.c
@@ -64,8 +64,8 @@
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 @@
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 0823679..8cf0106 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>
+#include <linux/sched.h>
+#include <linux/sched/task.h>
+#include <linux/sched/signal.h>
+
+#include "cgroup-internal.h"
+
+#include <trace/events/cgroup.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.
+ * Propagate the cgroup frozen state upwards by the cgroup tree.
*/
-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)
+static void cgroup_propagate_frozen(struct cgroup *cgrp, bool frozen)
{
- 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);
+ int desc = 1;
/*
- * 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.
+ * If the new state is frozen, some freezing ancestor cgroups may change
+ * their state too, depending on if all their descendants are frozen.
*
- * 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.
+ * Otherwise, all ancestor cgroups are forced into the non-frozen state.
*/
- cgroup_taskset_for_each(task, new_css, tset) {
- struct freezer *freezer = css_freezer(new_css);
-
- if (!(freezer->state & CGROUP_FREEZING)) {
- __thaw_task(task);
+ 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 {
- freeze_task(task);
- /* clear FROZEN and propagate upwards */
- while (freezer && (freezer->state & CGROUP_FROZEN)) {
- freezer->state &= ~CGROUP_FROZEN;
- freezer = parent_freezer(freezer);
+ 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++;
}
}
}
-
- 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.
+/*
+ * Revisit the cgroup frozen state.
+ * Checks if the cgroup is really frozen and perform all state transitions.
*/
-static void freezer_fork(struct task_struct *task)
+void cgroup_update_frozen(struct cgroup *cgrp)
{
- struct freezer *freezer;
+ bool frozen;
+
+ lockdep_assert_held(&css_set_lock);
/*
- * 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 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.
*/
- if (task_css_is_root(task, freezer_cgrp_id))
- return;
+ frozen = test_bit(CGRP_FREEZE, &cgrp->flags) &&
+ cgrp->freezer.nr_frozen_tasks == __cgroup_task_count(cgrp);
- 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();
+ if (frozen) {
+ /* Already there? */
+ if (test_bit(CGRP_FROZEN, &cgrp->flags))
return;
- }
+
+ set_bit(CGRP_FROZEN, &cgrp->flags);
+ } else {
+ /* Already there? */
+ if (!test_bit(CGRP_FROZEN, &cgrp->flags))
+ return;
+
+ clear_bit(CGRP_FROZEN, &cgrp->flags);
}
- rcu_read_unlock();
+ cgroup_file_notify(&cgrp->events_file);
+ TRACE_CGROUP_PATH(notify_frozen, cgrp, frozen);
- /* 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);
+ /* Update the state of ancestor cgroups. */
+ cgroup_propagate_frozen(cgrp, frozen);
}
-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.
+/*
+ * Increment cgroup's nr_frozen_tasks.
*/
-static void freezer_apply_state(struct freezer *freezer, bool freeze,
- unsigned int state)
+static void cgroup_inc_frozen_cnt(struct cgroup *cgrp)
{
- /* also synchronizes against task migration, see freezer_attach() */
- lockdep_assert_held(&freezer_mutex);
+ cgrp->freezer.nr_frozen_tasks++;
+}
- if (!(freezer->state & CGROUP_FREEZER_ONLINE))
+/*
+ * Decrement cgroup's nr_frozen_tasks.
+ */
+static void cgroup_dec_frozen_cnt(struct cgroup *cgrp)
+{
+ cgrp->freezer.nr_frozen_tasks--;
+ WARN_ON_ONCE(cgrp->freezer.nr_frozen_tasks < 0);
+}
+
+/*
+ * 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)
+{
+ 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);
+}
+
+/*
+ * Conditionally leave frozen/stopped state. Update cgroup's counters,
+ * and revisit the state of the cgroup, if necessary.
+ *
+ * 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.
+ */
+void cgroup_leave_frozen(bool always_leave)
+{
+ 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(¤t->sighand->siglock);
+ current->jobctl |= JOBCTL_TRAP_FREEZE;
+ set_thread_flag(TIF_SIGPENDING);
+ spin_unlock(¤t->sighand->siglock);
+ }
+ spin_unlock_irq(&css_set_lock);
+}
+
+/*
+ * Freeze or unfreeze the task by setting or clearing the JOBCTL_TRAP_FREEZE
+ * jobctl bit.
+ */
+static void cgroup_freeze_task(struct task_struct *task, bool freeze)
+{
+ unsigned long flags;
+
+ /* If the task is about to die, don't bother with freezing it. */
+ if (!lock_task_sighand(task, &flags))
return;
if (freeze) {
- if (!(freezer->state & CGROUP_FREEZING))
- atomic_inc(&system_freezing_cnt);
- freezer->state |= state;
- freeze_cgroup(freezer);
+ task->jobctl |= JOBCTL_TRAP_FREEZE;
+ signal_wake_up(task, false);
} 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);
- }
+ task->jobctl &= ~JOBCTL_TRAP_FREEZE;
+ wake_up_process(task);
}
+
+ unlock_task_sighand(task, &flags);
}
-/**
- * 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.
+/*
+ * Freeze or unfreeze all tasks in the given cgroup.
*/
-static void freezer_change_state(struct freezer *freezer, bool freeze)
+static void cgroup_do_freeze(struct cgroup *cgrp, bool freeze)
{
- struct cgroup_subsys_state *pos;
+ struct css_task_iter it;
+ struct task_struct *task;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ 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);
+
+ 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))) {
+ /*
+ * Ignore kernel threads here. Freezing cgroups containing
+ * kthreads isn't supported.
+ */
+ if (task->flags & PF_KTHREAD)
+ continue;
+ cgroup_freeze_task(task, freeze);
+ }
+ css_task_iter_end(&it);
/*
- * Update all its descendants in pre-order traversal. Each
- * descendant will try to inherit its parent's FREEZING state as
- * CGROUP_FREEZING_PARENT.
+ * Cgroup state should be revisited here to cover empty leaf cgroups
+ * and cgroups which descendants are already in 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);
+ 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);
+}
- if (!css_tryget_online(pos))
- continue;
- rcu_read_unlock();
+/*
+ * Adjust the task state (freeze or unfreeze) and revisit the state of
+ * source and destination cgroups.
+ */
+void cgroup_freezer_migrate_task(struct task_struct *task,
+ struct cgroup *src, struct cgroup *dst)
+{
+ lockdep_assert_held(&css_set_lock);
- 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);
+ /*
+ * Kernel threads are not supposed to be frozen at all.
+ */
+ if (task->flags & PF_KTHREAD)
+ return;
- rcu_read_lock();
- css_put(pos);
+ /*
+ * 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);
}
- rcu_read_unlock();
- mutex_unlock(&freezer_mutex);
+ cgroup_update_frozen(dst);
+ cgroup_update_frozen(src);
+
+ /*
+ * Force the task to the desired state.
+ */
+ 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;
+
+ /*
+ * Propagate changes downwards the cgroup tree.
+ */
+ css_for_each_descendant_pre(css, &cgrp->self) {
+ dsct = css->cgroup;
+
+ if (cgroup_is_dead(dsct))
+ continue;
+
+ 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;
+
+ WARN_ON_ONCE(dsct->freezer.e_freeze < 0);
+ }
+
+ /*
+ * Do change actual state: freeze or unfreeze.
+ */
+ cgroup_do_freeze(dsct, freeze);
+ applied = true;
+ }
+
+ /*
+ * 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);
+ }
}
-
-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,
-};
diff --git a/kernel/cgroup/legacy_freezer.c b/kernel/cgroup/legacy_freezer.c
new file mode 100644
index 0000000..0823679
--- /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,
+};
diff --git a/kernel/fork.c b/kernel/fork.c
index 8b03d93..5359fac 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1225,7 +1225,9 @@
int killed;
freezer_do_not_count();
+ cgroup_enter_frozen();
killed = wait_for_completion_killable(vfork);
+ cgroup_leave_frozen(false);
freezer_count();
if (killed) {
diff --git a/kernel/signal.c b/kernel/signal.c
index cd83cc3..62f9aea 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -43,6 +43,7 @@
#include <linux/compiler.h>
#include <linux/posix-timers.h>
#include <linux/livepatch.h>
+#include <linux/cgroup.h>
#define CREATE_TRACE_POINTS
#include <trace/events/signal.h>
@@ -146,9 +147,10 @@
static bool recalc_sigpending_tsk(struct task_struct *t)
{
- if ((t->jobctl & JOBCTL_PENDING_MASK) ||
+ if ((t->jobctl & (JOBCTL_PENDING_MASK | JOBCTL_TRAP_FREEZE)) ||
PENDING(&t->pending, &t->blocked) ||
- PENDING(&t->signal->shared_pending, &t->blocked)) {
+ PENDING(&t->signal->shared_pending, &t->blocked) ||
+ cgroup_task_frozen(t)) {
set_tsk_thread_flag(t, TIF_SIGPENDING);
return true;
}
@@ -2108,6 +2110,7 @@
preempt_disable();
read_unlock(&tasklist_lock);
preempt_enable_no_resched();
+ cgroup_enter_frozen();
freezable_schedule();
} else {
/*
@@ -2286,6 +2289,7 @@
}
/* Now we don't run again until woken by SIGCONT or SIGKILL */
+ cgroup_enter_frozen();
freezable_schedule();
return true;
} else {
@@ -2332,6 +2336,43 @@
}
}
+/**
+ * do_freezer_trap - handle the freezer jobctl trap
+ *
+ * Puts the task into frozen state, if only the task is not about to quit.
+ * In this case it drops JOBCTL_TRAP_FREEZE.
+ *
+ * CONTEXT:
+ * Must be called with @current->sighand->siglock held,
+ * which is always released before returning.
+ */
+static void do_freezer_trap(void)
+ __releases(¤t->sighand->siglock)
+{
+ /*
+ * If there are other trap bits pending except JOBCTL_TRAP_FREEZE,
+ * let's make another loop to give it a chance to be handled.
+ * In any case, we'll return back.
+ */
+ if ((current->jobctl & (JOBCTL_PENDING_MASK | JOBCTL_TRAP_FREEZE)) !=
+ JOBCTL_TRAP_FREEZE) {
+ spin_unlock_irq(¤t->sighand->siglock);
+ return;
+ }
+
+ /*
+ * Now we're sure that there is no pending fatal signal and no
+ * pending traps. Clear TIF_SIGPENDING to not get out of schedule()
+ * immediately (if there is a non-fatal signal pending), and
+ * put the task into sleep.
+ */
+ __set_current_state(TASK_INTERRUPTIBLE);
+ clear_thread_flag(TIF_SIGPENDING);
+ spin_unlock_irq(¤t->sighand->siglock);
+ cgroup_enter_frozen();
+ freezable_schedule();
+}
+
static int ptrace_signal(int signr, kernel_siginfo_t *info)
{
/*
@@ -2452,9 +2493,24 @@
do_signal_stop(0))
goto relock;
- if (unlikely(current->jobctl & JOBCTL_TRAP_MASK)) {
- do_jobctl_trap();
+ if (unlikely(current->jobctl &
+ (JOBCTL_TRAP_MASK | JOBCTL_TRAP_FREEZE))) {
+ if (current->jobctl & JOBCTL_TRAP_MASK) {
+ do_jobctl_trap();
+ spin_unlock_irq(&sighand->siglock);
+ } else if (current->jobctl & JOBCTL_TRAP_FREEZE)
+ do_freezer_trap();
+
+ goto relock;
+ }
+
+ /*
+ * If the task is leaving the frozen state, let's update
+ * cgroup counters and reset the frozen bit.
+ */
+ if (unlikely(cgroup_task_frozen(current))) {
spin_unlock_irq(&sighand->siglock);
+ cgroup_leave_frozen(false);
goto relock;
}
@@ -2550,6 +2606,8 @@
fatal:
spin_unlock_irq(&sighand->siglock);
+ if (unlikely(cgroup_task_frozen(current)))
+ cgroup_leave_frozen(true);
/*
* Anything else is fatal, maybe with a core dump.
diff --git a/tools/testing/selftests/cgroup/.gitignore b/tools/testing/selftests/cgroup/.gitignore
index adacda5..7f98356 100644
--- a/tools/testing/selftests/cgroup/.gitignore
+++ b/tools/testing/selftests/cgroup/.gitignore
@@ -1,2 +1,3 @@
test_memcontrol
test_core
+test_freezer
diff --git a/tools/testing/selftests/cgroup/Makefile b/tools/testing/selftests/cgroup/Makefile
index 23fbaa4..8d369b6 100644
--- a/tools/testing/selftests/cgroup/Makefile
+++ b/tools/testing/selftests/cgroup/Makefile
@@ -5,8 +5,10 @@
TEST_GEN_PROGS = test_memcontrol
TEST_GEN_PROGS += test_core
+TEST_GEN_PROGS += test_freezer
include ../lib.mk
$(OUTPUT)/test_memcontrol: cgroup_util.c
$(OUTPUT)/test_core: cgroup_util.c
+$(OUTPUT)/test_freezer: cgroup_util.c
diff --git a/tools/testing/selftests/cgroup/cgroup_util.c b/tools/testing/selftests/cgroup/cgroup_util.c
index 14c9fe2..4c22326 100644
--- a/tools/testing/selftests/cgroup/cgroup_util.c
+++ b/tools/testing/selftests/cgroup/cgroup_util.c
@@ -74,6 +74,16 @@
return ret;
}
+char *cg_control(const char *cgroup, const char *control)
+{
+ size_t len = strlen(cgroup) + strlen(control) + 2;
+ char *ret = malloc(len);
+
+ snprintf(ret, len, "%s/%s", cgroup, control);
+
+ return ret;
+}
+
int cg_read(const char *cgroup, const char *control, char *buf, size_t len)
{
char path[PATH_MAX];
@@ -196,7 +206,32 @@
return mkdir(cgroup, 0644);
}
-static int cg_killall(const char *cgroup)
+int cg_wait_for_proc_count(const char *cgroup, int count)
+{
+ char buf[10 * PAGE_SIZE] = {0};
+ int attempts;
+ char *ptr;
+
+ for (attempts = 10; attempts >= 0; attempts--) {
+ int nr = 0;
+
+ if (cg_read(cgroup, "cgroup.procs", buf, sizeof(buf)))
+ break;
+
+ for (ptr = buf; *ptr; ptr++)
+ if (*ptr == '\n')
+ nr++;
+
+ if (nr >= count)
+ return 0;
+
+ usleep(100000);
+ }
+
+ return -1;
+}
+
+int cg_killall(const char *cgroup)
{
char buf[PAGE_SIZE];
char *ptr = buf;
@@ -227,9 +262,7 @@
retry:
ret = rmdir(cgroup);
if (ret && errno == EBUSY) {
- ret = cg_killall(cgroup);
- if (ret)
- return ret;
+ cg_killall(cgroup);
usleep(100);
goto retry;
}
@@ -240,6 +273,14 @@
return ret;
}
+int cg_enter(const char *cgroup, int pid)
+{
+ char pidbuf[64];
+
+ snprintf(pidbuf, sizeof(pidbuf), "%d", pid);
+ return cg_write(cgroup, "cgroup.procs", pidbuf);
+}
+
int cg_enter_current(const char *cgroup)
{
char pidbuf[64];
@@ -369,3 +410,12 @@
close(fd);
return 0;
}
+
+char proc_read_text(int pid, const char *item, char *buf, size_t size)
+{
+ char path[PATH_MAX];
+
+ snprintf(path, sizeof(path), "/proc/%d/%s", pid, item);
+
+ return read_text(path, buf, size);
+}
diff --git a/tools/testing/selftests/cgroup/cgroup_util.h b/tools/testing/selftests/cgroup/cgroup_util.h
index 9ac8b79..c72f280 100644
--- a/tools/testing/selftests/cgroup/cgroup_util.h
+++ b/tools/testing/selftests/cgroup/cgroup_util.h
@@ -18,6 +18,7 @@
extern int cg_find_unified_root(char *root, size_t len);
extern char *cg_name(const char *root, const char *name);
extern char *cg_name_indexed(const char *root, const char *name, int index);
+extern char *cg_control(const char *cgroup, const char *control);
extern int cg_create(const char *cgroup);
extern int cg_destroy(const char *cgroup);
extern int cg_read(const char *cgroup, const char *control,
@@ -32,6 +33,7 @@
extern int cg_run(const char *cgroup,
int (*fn)(const char *cgroup, void *arg),
void *arg);
+extern int cg_enter(const char *cgroup, int pid);
extern int cg_enter_current(const char *cgroup);
extern int cg_run_nowait(const char *cgroup,
int (*fn)(const char *cgroup, void *arg),
@@ -41,3 +43,6 @@
extern int alloc_anon(const char *cgroup, void *arg);
extern int is_swap_enabled(void);
extern int set_oom_adj_score(int pid, int score);
+extern int cg_wait_for_proc_count(const char *cgroup, int count);
+extern int cg_killall(const char *cgroup);
+extern char proc_read_text(int pid, const char *item, char *buf, size_t size);
diff --git a/tools/testing/selftests/cgroup/test_freezer.c b/tools/testing/selftests/cgroup/test_freezer.c
new file mode 100644
index 0000000..2bfddb6
--- /dev/null
+++ b/tools/testing/selftests/cgroup/test_freezer.c
@@ -0,0 +1,851 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <stdbool.h>
+#include <linux/limits.h>
+#include <sys/ptrace.h>
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <errno.h>
+#include <poll.h>
+#include <stdlib.h>
+#include <sys/inotify.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include "../kselftest.h"
+#include "cgroup_util.h"
+
+#define DEBUG
+#ifdef DEBUG
+#define debug(args...) fprintf(stderr, args)
+#else
+#define debug(args...)
+#endif
+
+/*
+ * Check if the cgroup is frozen by looking at the cgroup.events::frozen value.
+ */
+static int cg_check_frozen(const char *cgroup, bool frozen)
+{
+ if (frozen) {
+ if (cg_read_strstr(cgroup, "cgroup.events", "frozen 1") != 0) {
+ debug("Cgroup %s isn't frozen\n", cgroup);
+ return -1;
+ }
+ } else {
+ /*
+ * Check the cgroup.events::frozen value.
+ */
+ if (cg_read_strstr(cgroup, "cgroup.events", "frozen 0") != 0) {
+ debug("Cgroup %s is frozen\n", cgroup);
+ return -1;
+ }
+ }
+
+ return 0;
+}
+
+/*
+ * Freeze the given cgroup.
+ */
+static int cg_freeze_nowait(const char *cgroup, bool freeze)
+{
+ return cg_write(cgroup, "cgroup.freeze", freeze ? "1" : "0");
+}
+
+/*
+ * Prepare for waiting on cgroup.events file.
+ */
+static int cg_prepare_for_wait(const char *cgroup)
+{
+ int fd, ret = -1;
+
+ fd = inotify_init1(0);
+ if (fd == -1) {
+ debug("Error: inotify_init1() failed\n");
+ return fd;
+ }
+
+ ret = inotify_add_watch(fd, cg_control(cgroup, "cgroup.events"),
+ IN_MODIFY);
+ if (ret == -1) {
+ debug("Error: inotify_add_watch() failed\n");
+ close(fd);
+ }
+
+ return fd;
+}
+
+/*
+ * Wait for an event. If there are no events for 10 seconds,
+ * treat this an error.
+ */
+static int cg_wait_for(int fd)
+{
+ int ret = -1;
+ struct pollfd fds = {
+ .fd = fd,
+ .events = POLLIN,
+ };
+
+ while (true) {
+ ret = poll(&fds, 1, 10000);
+
+ if (ret == -1) {
+ if (errno == EINTR)
+ continue;
+ debug("Error: poll() failed\n");
+ break;
+ }
+
+ if (ret > 0 && fds.revents & POLLIN) {
+ ret = 0;
+ break;
+ }
+ }
+
+ return ret;
+}
+
+/*
+ * Attach a task to the given cgroup and wait for a cgroup frozen event.
+ * All transient events (e.g. populated) are ignored.
+ */
+static int cg_enter_and_wait_for_frozen(const char *cgroup, int pid,
+ bool frozen)
+{
+ int fd, ret = -1;
+ int attempts;
+
+ fd = cg_prepare_for_wait(cgroup);
+ if (fd < 0)
+ return fd;
+
+ ret = cg_enter(cgroup, pid);
+ if (ret)
+ goto out;
+
+ for (attempts = 0; attempts < 10; attempts++) {
+ ret = cg_wait_for(fd);
+ if (ret)
+ break;
+
+ ret = cg_check_frozen(cgroup, frozen);
+ if (ret)
+ continue;
+ }
+
+out:
+ close(fd);
+ return ret;
+}
+
+/*
+ * Freeze the given cgroup and wait for the inotify signal.
+ * If there are no events in 10 seconds, treat this as an error.
+ * Then check that the cgroup is in the desired state.
+ */
+static int cg_freeze_wait(const char *cgroup, bool freeze)
+{
+ int fd, ret = -1;
+
+ fd = cg_prepare_for_wait(cgroup);
+ if (fd < 0)
+ return fd;
+
+ ret = cg_freeze_nowait(cgroup, freeze);
+ if (ret) {
+ debug("Error: cg_freeze_nowait() failed\n");
+ goto out;
+ }
+
+ ret = cg_wait_for(fd);
+ if (ret)
+ goto out;
+
+ ret = cg_check_frozen(cgroup, freeze);
+out:
+ close(fd);
+ return ret;
+}
+
+/*
+ * A simple process running in a sleep loop until being
+ * re-parented.
+ */
+static int child_fn(const char *cgroup, void *arg)
+{
+ int ppid = getppid();
+
+ while (getppid() == ppid)
+ usleep(1000);
+
+ return getppid() == ppid;
+}
+
+/*
+ * A simple test for the cgroup freezer: populated the cgroup with 100
+ * running processes and freeze it. Then unfreeze it. Then it kills all
+ * processes and destroys the cgroup.
+ */
+static int test_cgfreezer_simple(const char *root)
+{
+ int ret = KSFT_FAIL;
+ char *cgroup = NULL;
+ int i;
+
+ cgroup = cg_name(root, "cg_test_simple");
+ if (!cgroup)
+ goto cleanup;
+
+ if (cg_create(cgroup))
+ goto cleanup;
+
+ for (i = 0; i < 100; i++)
+ cg_run_nowait(cgroup, child_fn, NULL);
+
+ if (cg_wait_for_proc_count(cgroup, 100))
+ goto cleanup;
+
+ if (cg_check_frozen(cgroup, false))
+ goto cleanup;
+
+ if (cg_freeze_wait(cgroup, true))
+ goto cleanup;
+
+ if (cg_freeze_wait(cgroup, false))
+ goto cleanup;
+
+ ret = KSFT_PASS;
+
+cleanup:
+ if (cgroup)
+ cg_destroy(cgroup);
+ free(cgroup);
+ return ret;
+}
+
+/*
+ * The test creates the following hierarchy:
+ * A
+ * / / \ \
+ * B E I K
+ * /\ |
+ * C D F
+ * |
+ * G
+ * |
+ * H
+ *
+ * with a process in C, H and 3 processes in K.
+ * Then it tries to freeze and unfreeze the whole tree.
+ */
+static int test_cgfreezer_tree(const char *root)
+{
+ char *cgroup[10] = {0};
+ int ret = KSFT_FAIL;
+ int i;
+
+ cgroup[0] = cg_name(root, "cg_test_tree_A");
+ if (!cgroup[0])
+ goto cleanup;
+
+ cgroup[1] = cg_name(cgroup[0], "B");
+ if (!cgroup[1])
+ goto cleanup;
+
+ cgroup[2] = cg_name(cgroup[1], "C");
+ if (!cgroup[2])
+ goto cleanup;
+
+ cgroup[3] = cg_name(cgroup[1], "D");
+ if (!cgroup[3])
+ goto cleanup;
+
+ cgroup[4] = cg_name(cgroup[0], "E");
+ if (!cgroup[4])
+ goto cleanup;
+
+ cgroup[5] = cg_name(cgroup[4], "F");
+ if (!cgroup[5])
+ goto cleanup;
+
+ cgroup[6] = cg_name(cgroup[5], "G");
+ if (!cgroup[6])
+ goto cleanup;
+
+ cgroup[7] = cg_name(cgroup[6], "H");
+ if (!cgroup[7])
+ goto cleanup;
+
+ cgroup[8] = cg_name(cgroup[0], "I");
+ if (!cgroup[8])
+ goto cleanup;
+
+ cgroup[9] = cg_name(cgroup[0], "K");
+ if (!cgroup[9])
+ goto cleanup;
+
+ for (i = 0; i < 10; i++)
+ if (cg_create(cgroup[i]))
+ goto cleanup;
+
+ cg_run_nowait(cgroup[2], child_fn, NULL);
+ cg_run_nowait(cgroup[7], child_fn, NULL);
+ cg_run_nowait(cgroup[9], child_fn, NULL);
+ cg_run_nowait(cgroup[9], child_fn, NULL);
+ cg_run_nowait(cgroup[9], child_fn, NULL);
+
+ /*
+ * Wait until all child processes will enter
+ * corresponding cgroups.
+ */
+
+ if (cg_wait_for_proc_count(cgroup[2], 1) ||
+ cg_wait_for_proc_count(cgroup[7], 1) ||
+ cg_wait_for_proc_count(cgroup[9], 3))
+ goto cleanup;
+
+ /*
+ * Freeze B.
+ */
+ if (cg_freeze_wait(cgroup[1], true))
+ goto cleanup;
+
+ /*
+ * Freeze F.
+ */
+ if (cg_freeze_wait(cgroup[5], true))
+ goto cleanup;
+
+ /*
+ * Freeze G.
+ */
+ if (cg_freeze_wait(cgroup[6], true))
+ goto cleanup;
+
+ /*
+ * Check that A and E are not frozen.
+ */
+ if (cg_check_frozen(cgroup[0], false))
+ goto cleanup;
+
+ if (cg_check_frozen(cgroup[4], false))
+ goto cleanup;
+
+ /*
+ * Freeze A. Check that A, B and E are frozen.
+ */
+ if (cg_freeze_wait(cgroup[0], true))
+ goto cleanup;
+
+ if (cg_check_frozen(cgroup[1], true))
+ goto cleanup;
+
+ if (cg_check_frozen(cgroup[4], true))
+ goto cleanup;
+
+ /*
+ * Unfreeze B, F and G
+ */
+ if (cg_freeze_nowait(cgroup[1], false))
+ goto cleanup;
+
+ if (cg_freeze_nowait(cgroup[5], false))
+ goto cleanup;
+
+ if (cg_freeze_nowait(cgroup[6], false))
+ goto cleanup;
+
+ /*
+ * Check that C and H are still frozen.
+ */
+ if (cg_check_frozen(cgroup[2], true))
+ goto cleanup;
+
+ if (cg_check_frozen(cgroup[7], true))
+ goto cleanup;
+
+ /*
+ * Unfreeze A. Check that A, C and K are not frozen.
+ */
+ if (cg_freeze_wait(cgroup[0], false))
+ goto cleanup;
+
+ if (cg_check_frozen(cgroup[2], false))
+ goto cleanup;
+
+ if (cg_check_frozen(cgroup[9], false))
+ goto cleanup;
+
+ ret = KSFT_PASS;
+
+cleanup:
+ for (i = 9; i >= 0 && cgroup[i]; i--) {
+ cg_destroy(cgroup[i]);
+ free(cgroup[i]);
+ }
+
+ return ret;
+}
+
+/*
+ * A fork bomb emulator.
+ */
+static int forkbomb_fn(const char *cgroup, void *arg)
+{
+ int ppid;
+
+ fork();
+ fork();
+
+ ppid = getppid();
+
+ while (getppid() == ppid)
+ usleep(1000);
+
+ return getppid() == ppid;
+}
+
+/*
+ * The test runs a fork bomb in a cgroup and tries to freeze it.
+ * Then it kills all processes and checks that cgroup isn't populated
+ * anymore.
+ */
+static int test_cgfreezer_forkbomb(const char *root)
+{
+ int ret = KSFT_FAIL;
+ char *cgroup = NULL;
+
+ cgroup = cg_name(root, "cg_forkbomb_test");
+ if (!cgroup)
+ goto cleanup;
+
+ if (cg_create(cgroup))
+ goto cleanup;
+
+ cg_run_nowait(cgroup, forkbomb_fn, NULL);
+
+ usleep(100000);
+
+ if (cg_freeze_wait(cgroup, true))
+ goto cleanup;
+
+ if (cg_killall(cgroup))
+ goto cleanup;
+
+ if (cg_wait_for_proc_count(cgroup, 0))
+ goto cleanup;
+
+ ret = KSFT_PASS;
+
+cleanup:
+ if (cgroup)
+ cg_destroy(cgroup);
+ free(cgroup);
+ return ret;
+}
+
+/*
+ * The test creates two nested cgroups, freezes the parent
+ * and removes the child. Then it checks that the parent cgroup
+ * remains frozen and it's possible to create a new child
+ * without unfreezing. The new child is frozen too.
+ */
+static int test_cgfreezer_rmdir(const char *root)
+{
+ int ret = KSFT_FAIL;
+ char *parent, *child = NULL;
+
+ parent = cg_name(root, "cg_test_rmdir_A");
+ if (!parent)
+ goto cleanup;
+
+ child = cg_name(parent, "cg_test_rmdir_B");
+ if (!child)
+ goto cleanup;
+
+ if (cg_create(parent))
+ goto cleanup;
+
+ if (cg_create(child))
+ goto cleanup;
+
+ if (cg_freeze_wait(parent, true))
+ goto cleanup;
+
+ if (cg_destroy(child))
+ goto cleanup;
+
+ if (cg_check_frozen(parent, true))
+ goto cleanup;
+
+ if (cg_create(child))
+ goto cleanup;
+
+ if (cg_check_frozen(child, true))
+ goto cleanup;
+
+ ret = KSFT_PASS;
+
+cleanup:
+ if (child)
+ cg_destroy(child);
+ free(child);
+ if (parent)
+ cg_destroy(parent);
+ free(parent);
+ return ret;
+}
+
+/*
+ * The test creates two cgroups: A and B, runs a process in A
+ * and performs several migrations:
+ * 1) A (running) -> B (frozen)
+ * 2) B (frozen) -> A (running)
+ * 3) A (frozen) -> B (frozen)
+ *
+ * On each step it checks the actual state of both cgroups.
+ */
+static int test_cgfreezer_migrate(const char *root)
+{
+ int ret = KSFT_FAIL;
+ char *cgroup[2] = {0};
+ int pid;
+
+ cgroup[0] = cg_name(root, "cg_test_migrate_A");
+ if (!cgroup[0])
+ goto cleanup;
+
+ cgroup[1] = cg_name(root, "cg_test_migrate_B");
+ if (!cgroup[1])
+ goto cleanup;
+
+ if (cg_create(cgroup[0]))
+ goto cleanup;
+
+ if (cg_create(cgroup[1]))
+ goto cleanup;
+
+ pid = cg_run_nowait(cgroup[0], child_fn, NULL);
+ if (pid < 0)
+ goto cleanup;
+
+ if (cg_wait_for_proc_count(cgroup[0], 1))
+ goto cleanup;
+
+ /*
+ * Migrate from A (running) to B (frozen)
+ */
+ if (cg_freeze_wait(cgroup[1], true))
+ goto cleanup;
+
+ if (cg_enter_and_wait_for_frozen(cgroup[1], pid, true))
+ goto cleanup;
+
+ if (cg_check_frozen(cgroup[0], false))
+ goto cleanup;
+
+ /*
+ * Migrate from B (frozen) to A (running)
+ */
+ if (cg_enter_and_wait_for_frozen(cgroup[0], pid, false))
+ goto cleanup;
+
+ if (cg_check_frozen(cgroup[1], true))
+ goto cleanup;
+
+ /*
+ * Migrate from A (frozen) to B (frozen)
+ */
+ if (cg_freeze_wait(cgroup[0], true))
+ goto cleanup;
+
+ if (cg_enter_and_wait_for_frozen(cgroup[1], pid, true))
+ goto cleanup;
+
+ if (cg_check_frozen(cgroup[0], true))
+ goto cleanup;
+
+ ret = KSFT_PASS;
+
+cleanup:
+ if (cgroup[0])
+ cg_destroy(cgroup[0]);
+ free(cgroup[0]);
+ if (cgroup[1])
+ cg_destroy(cgroup[1]);
+ free(cgroup[1]);
+ return ret;
+}
+
+/*
+ * The test checks that ptrace works with a tracing process in a frozen cgroup.
+ */
+static int test_cgfreezer_ptrace(const char *root)
+{
+ int ret = KSFT_FAIL;
+ char *cgroup = NULL;
+ siginfo_t siginfo;
+ int pid;
+
+ cgroup = cg_name(root, "cg_test_ptrace");
+ if (!cgroup)
+ goto cleanup;
+
+ if (cg_create(cgroup))
+ goto cleanup;
+
+ pid = cg_run_nowait(cgroup, child_fn, NULL);
+ if (pid < 0)
+ goto cleanup;
+
+ if (cg_wait_for_proc_count(cgroup, 1))
+ goto cleanup;
+
+ if (cg_freeze_wait(cgroup, true))
+ goto cleanup;
+
+ if (ptrace(PTRACE_SEIZE, pid, NULL, NULL))
+ goto cleanup;
+
+ if (ptrace(PTRACE_INTERRUPT, pid, NULL, NULL))
+ goto cleanup;
+
+ waitpid(pid, NULL, 0);
+
+ /*
+ * Cgroup has to remain frozen, however the test task
+ * is in traced state.
+ */
+ if (cg_check_frozen(cgroup, true))
+ goto cleanup;
+
+ if (ptrace(PTRACE_GETSIGINFO, pid, NULL, &siginfo))
+ goto cleanup;
+
+ if (ptrace(PTRACE_DETACH, pid, NULL, NULL))
+ goto cleanup;
+
+ if (cg_check_frozen(cgroup, true))
+ goto cleanup;
+
+ ret = KSFT_PASS;
+
+cleanup:
+ if (cgroup)
+ cg_destroy(cgroup);
+ free(cgroup);
+ return ret;
+}
+
+/*
+ * Check if the process is stopped.
+ */
+static int proc_check_stopped(int pid)
+{
+ char buf[PAGE_SIZE];
+ int len;
+
+ len = proc_read_text(pid, "stat", buf, sizeof(buf));
+ if (len == -1) {
+ debug("Can't get %d stat\n", pid);
+ return -1;
+ }
+
+ if (strstr(buf, "(test_freezer) T ") == NULL) {
+ debug("Process %d in the unexpected state: %s\n", pid, buf);
+ return -1;
+ }
+
+ return 0;
+}
+
+/*
+ * Test that it's possible to freeze a cgroup with a stopped process.
+ */
+static int test_cgfreezer_stopped(const char *root)
+{
+ int pid, ret = KSFT_FAIL;
+ char *cgroup = NULL;
+
+ cgroup = cg_name(root, "cg_test_stopped");
+ if (!cgroup)
+ goto cleanup;
+
+ if (cg_create(cgroup))
+ goto cleanup;
+
+ pid = cg_run_nowait(cgroup, child_fn, NULL);
+
+ if (cg_wait_for_proc_count(cgroup, 1))
+ goto cleanup;
+
+ if (kill(pid, SIGSTOP))
+ goto cleanup;
+
+ if (cg_check_frozen(cgroup, false))
+ goto cleanup;
+
+ if (cg_freeze_wait(cgroup, true))
+ goto cleanup;
+
+ if (cg_freeze_wait(cgroup, false))
+ goto cleanup;
+
+ if (proc_check_stopped(pid))
+ goto cleanup;
+
+ ret = KSFT_PASS;
+
+cleanup:
+ if (cgroup)
+ cg_destroy(cgroup);
+ free(cgroup);
+ return ret;
+}
+
+/*
+ * Test that it's possible to freeze a cgroup with a ptraced process.
+ */
+static int test_cgfreezer_ptraced(const char *root)
+{
+ int pid, ret = KSFT_FAIL;
+ char *cgroup = NULL;
+ siginfo_t siginfo;
+
+ cgroup = cg_name(root, "cg_test_ptraced");
+ if (!cgroup)
+ goto cleanup;
+
+ if (cg_create(cgroup))
+ goto cleanup;
+
+ pid = cg_run_nowait(cgroup, child_fn, NULL);
+
+ if (cg_wait_for_proc_count(cgroup, 1))
+ goto cleanup;
+
+ if (ptrace(PTRACE_SEIZE, pid, NULL, NULL))
+ goto cleanup;
+
+ if (ptrace(PTRACE_INTERRUPT, pid, NULL, NULL))
+ goto cleanup;
+
+ waitpid(pid, NULL, 0);
+
+ if (cg_check_frozen(cgroup, false))
+ goto cleanup;
+
+ if (cg_freeze_wait(cgroup, true))
+ goto cleanup;
+
+ /*
+ * cg_check_frozen(cgroup, true) will fail here,
+ * because the task in in the TRACEd state.
+ */
+ if (cg_freeze_wait(cgroup, false))
+ goto cleanup;
+
+ if (ptrace(PTRACE_GETSIGINFO, pid, NULL, &siginfo))
+ goto cleanup;
+
+ if (ptrace(PTRACE_DETACH, pid, NULL, NULL))
+ goto cleanup;
+
+ ret = KSFT_PASS;
+
+cleanup:
+ if (cgroup)
+ cg_destroy(cgroup);
+ free(cgroup);
+ return ret;
+}
+
+static int vfork_fn(const char *cgroup, void *arg)
+{
+ int pid = vfork();
+
+ if (pid == 0)
+ while (true)
+ sleep(1);
+
+ return pid;
+}
+
+/*
+ * Test that it's possible to freeze a cgroup with a process,
+ * which called vfork() and is waiting for a child.
+ */
+static int test_cgfreezer_vfork(const char *root)
+{
+ int ret = KSFT_FAIL;
+ char *cgroup = NULL;
+
+ cgroup = cg_name(root, "cg_test_vfork");
+ if (!cgroup)
+ goto cleanup;
+
+ if (cg_create(cgroup))
+ goto cleanup;
+
+ cg_run_nowait(cgroup, vfork_fn, NULL);
+
+ if (cg_wait_for_proc_count(cgroup, 2))
+ goto cleanup;
+
+ if (cg_freeze_wait(cgroup, true))
+ goto cleanup;
+
+ ret = KSFT_PASS;
+
+cleanup:
+ if (cgroup)
+ cg_destroy(cgroup);
+ free(cgroup);
+ return ret;
+}
+
+#define T(x) { x, #x }
+struct cgfreezer_test {
+ int (*fn)(const char *root);
+ const char *name;
+} tests[] = {
+ T(test_cgfreezer_simple),
+ T(test_cgfreezer_tree),
+ T(test_cgfreezer_forkbomb),
+ T(test_cgfreezer_rmdir),
+ T(test_cgfreezer_migrate),
+ T(test_cgfreezer_ptrace),
+ T(test_cgfreezer_stopped),
+ T(test_cgfreezer_ptraced),
+ T(test_cgfreezer_vfork),
+};
+#undef T
+
+int main(int argc, char *argv[])
+{
+ char root[PATH_MAX];
+ int i, ret = EXIT_SUCCESS;
+
+ if (cg_find_unified_root(root, sizeof(root)))
+ ksft_exit_skip("cgroup v2 isn't mounted\n");
+ for (i = 0; i < ARRAY_SIZE(tests); i++) {
+ switch (tests[i].fn(root)) {
+ case KSFT_PASS:
+ ksft_test_result_pass("%s\n", tests[i].name);
+ break;
+ case KSFT_SKIP:
+ ksft_test_result_skip("%s\n", tests[i].name);
+ break;
+ default:
+ ret = EXIT_FAILURE;
+ ksft_test_result_fail("%s\n", tests[i].name);
+ break;
+ }
+ }
+
+ return ret;
+}
