Merge tag 'cgroup-for-6.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:

 - Added Michal Koutný as a maintainer

 - Counters in pids.events were behaving inconsistently. pids.events
   made properly hierarchical and pids.events.local added

 - misc.peak and misc.events.local added

 - cpuset remote partition creation and cpuset.cpus.exclusive handling
   improved

 - Code cleanups, non-critical fixes, doc updates

 - for-6.10-fixes is merged in to receive two non-critical fixes that
   didn't trigger pull

* tag 'cgroup-for-6.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (23 commits)
  cgroup: Add Michal Koutný as a maintainer
  cgroup/misc: Introduce misc.events.local
  cgroup/rstat: add force idle show helper
  cgroup: Protect css->cgroup write under css_set_lock
  cgroup/misc: Introduce misc.peak
  cgroup_misc: add kernel-doc comments for enum misc_res_type
  cgroup/cpuset: Prevent UAF in proc_cpuset_show()
  selftest/cgroup: Update test_cpuset_prs.sh to match changes
  cgroup/cpuset: Make cpuset.cpus.exclusive independent of cpuset.cpus
  cgroup/cpuset: Delay setting of CS_CPU_EXCLUSIVE until valid partition
  selftest/cgroup: Fix test_cpuset_prs.sh problems reported by test robot
  cgroup/cpuset: Fix remote root partition creation problem
  cgroup: avoid the unnecessary list_add(dying_tasks) in cgroup_exit()
  cgroup/cpuset: Optimize isolated partition only generate_sched_domains() calls
  cgroup/cpuset: Reduce the lock protecting CS_SCHED_LOAD_BALANCE
  kernel/cgroup: cleanup cgroup_base_files when fail to add cgroup_psi_files
  selftests: cgroup: Add basic tests for pids controller
  selftests: cgroup: Lexicographic order in Makefile
  cgroup/pids: Add pids.events.local
  cgroup/pids: Make event counters hierarchical
  ...

Documentation/admin-guide/cgroup-v1/pids.rst

@@ -36,7 +36,8 @@ superset of parent/child/pids.current.
 
 The pids.events file contains event counters:
 
-  - max: Number of times fork failed because limit was hit.
+  - max: Number of times fork failed in the cgroup because limit was hit in
+    self or ancestors.
 
 Example
 -------

Documentation/admin-guide/cgroup-v2.rst

@@ -239,6 +239,13 @@ cgroup v2 currently supports the following mount options.
           will not be tracked by the memory controller (even if cgroup
           v2 is remounted later on).
 
+  pids_localevents
+        The option restores v1-like behavior of pids.events:max, that is only
+        local (inside cgroup proper) fork failures are counted. Without this
+        option pids.events.max represents any pids.max enforcemnt across
+        cgroup's subtree.
+
+
 
 Organizing Processes and Threads
 --------------------------------
@@ -2205,12 +2212,18 @@ PID Interface Files
 	descendants has ever reached.
 
   pids.events
-	A read-only flat-keyed file which exists on non-root cgroups. The
-	following entries are defined. Unless specified otherwise, a value
-	change in this file generates a file modified event.
+	A read-only flat-keyed file which exists on non-root cgroups. Unless
+	specified otherwise, a value change in this file generates a file
+	modified event. The following entries are defined.
 
 	  max
-		Number of times fork failed because limit was hit.
+		The number of times the cgroup's total number of processes hit the pids.max
+		limit (see also pids_localevents).
+
+  pids.events.local
+	Similar to pids.events but the fields in the file are local
+	to the cgroup i.e. not hierarchical. The file modified event
+	generated on this file reflects only the local events.
 
 Organisational operations are not blocked by cgroup policies, so it is
 possible to have pids.current > pids.max.  This can be done by either
@@ -2346,8 +2359,12 @@ Cpuset Interface Files
 	is always a subset of it.
 
 	Users can manually set it to a value that is different from
-	"cpuset.cpus".	The only constraint in setting it is that the
-	list of CPUs must be exclusive with respect to its sibling.
+	"cpuset.cpus".	One constraint in setting it is that the list of
+	CPUs must be exclusive with respect to "cpuset.cpus.exclusive"
+	of its sibling.  If "cpuset.cpus.exclusive" of a sibling cgroup
+	isn't set, its "cpuset.cpus" value, if set, cannot be a subset
+	of it to leave at least one CPU available when the exclusive
+	CPUs are taken away.
 
 	For a parent cgroup, any one of its exclusive CPUs can only
 	be distributed to at most one of its child cgroups.  Having an
@@ -2363,8 +2380,8 @@ Cpuset Interface Files
 	cpuset-enabled cgroups.
 
 	This file shows the effective set of exclusive CPUs that
-	can be used to create a partition root.  The content of this
-	file will always be a subset of "cpuset.cpus" and its parent's
+	can be used to create a partition root.  The content
+	of this file will always be a subset of its parent's
 	"cpuset.cpus.exclusive.effective" if its parent is not the root
 	cgroup.  It will also be a subset of "cpuset.cpus.exclusive"
 	if it is set.  If "cpuset.cpus.exclusive" is not set, it is
@@ -2625,6 +2642,15 @@ Miscellaneous controller provides 3 interface files. If two misc resources (res_
 	  res_a 3
 	  res_b 0
 
+  misc.peak
+        A read-only flat-keyed file shown in all cgroups.  It shows the
+        historical maximum usage of the resources in the cgroup and its
+        children.::
+
+	  $ cat misc.peak
+	  res_a 10
+	  res_b 8
+
   misc.max
         A read-write flat-keyed file shown in the non root cgroups. Allowed
         maximum usage of the resources in the cgroup and its children.::
@@ -2654,6 +2680,11 @@ Miscellaneous controller provides 3 interface files. If two misc resources (res_
 		The number of times the cgroup's resource usage was
 		about to go over the max boundary.
 
+  misc.events.local
+        Similar to misc.events but the fields in the file are local to the
+        cgroup i.e. not hierarchical. The file modified event generated on
+        this file reflects only the local events.
+
 Migration and Ownership
 ~~~~~~~~~~~~~~~~~~~~~~~
 

MAINTAINERS

@@ -5528,6 +5528,7 @@ CONTROL GROUP (CGROUP)
 M:	Tejun Heo <tj@kernel.org>
 M:	Zefan Li <lizefan.x@bytedance.com>
 M:	Johannes Weiner <hannes@cmpxchg.org>
+M:	Michal Koutný <mkoutny@suse.com>
 L:	cgroups@vger.kernel.org
 S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git

include/linux/cgroup-defs.h

@@ -119,7 +119,12 @@ enum {
 	/*
 	 * Enable hugetlb accounting for the memory controller.
 	 */
-	 CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING = (1 << 19),
+	CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING = (1 << 19),
+
+	/*
+	 * Enable legacy local pids.events.
+	 */
+	CGRP_ROOT_PIDS_LOCAL_EVENTS = (1 << 20),
 };
 
 /* cftype->flags */

include/linux/misc_cgroup.h

@@ -9,15 +9,16 @@
 #define _MISC_CGROUP_H_
 
 /**
- * Types of misc cgroup entries supported by the host.
+ * enum misc_res_type - Types of misc cgroup entries supported by the host.
  */
 enum misc_res_type {
 #ifdef CONFIG_KVM_AMD_SEV
-	/* AMD SEV ASIDs resource */
+	/** @MISC_CG_RES_SEV: AMD SEV ASIDs resource */
 	MISC_CG_RES_SEV,
-	/* AMD SEV-ES ASIDs resource */
+	/** @MISC_CG_RES_SEV_ES: AMD SEV-ES ASIDs resource */
 	MISC_CG_RES_SEV_ES,
 #endif
+	/** @MISC_CG_RES_TYPES: count of enum misc_res_type constants */
 	MISC_CG_RES_TYPES
 };
 
@@ -30,13 +31,16 @@ struct misc_cg;
 /**
  * struct misc_res: Per cgroup per misc type resource
  * @max: Maximum limit on the resource.
+ * @watermark: Historical maximum usage of the resource.
  * @usage: Current usage of the resource.
  * @events: Number of times, the resource limit exceeded.
  */
 struct misc_res {
 	u64 max;
+	atomic64_t watermark;
 	atomic64_t usage;
 	atomic64_t events;
+	atomic64_t events_local;
 };
 
 /**
@@ -50,6 +54,8 @@ struct misc_cg {
 
 	/* misc.events */
 	struct cgroup_file events_file;
+	/* misc.events.local */
+	struct cgroup_file events_local_file;
 
 	struct misc_res res[MISC_CG_RES_TYPES];
 };

kernel/cgroup/cgroup.c

@@ -1744,8 +1744,11 @@ static int css_populate_dir(struct cgroup_subsys_state *css)
 			if (cgroup_psi_enabled()) {
 				ret = cgroup_addrm_files(css, cgrp,
 							 cgroup_psi_files, true);
-				if (ret < 0)
+				if (ret < 0) {
+					cgroup_addrm_files(css, cgrp,
+							   cgroup_base_files, false);
 					return ret;
+				}
 			}
 		} else {
 			ret = cgroup_addrm_files(css, cgrp,
@@ -1839,9 +1842,9 @@ int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask)
 		RCU_INIT_POINTER(scgrp->subsys[ssid], NULL);
 		rcu_assign_pointer(dcgrp->subsys[ssid], css);
 		ss->root = dst_root;
-		css->cgroup = dcgrp;
 
 		spin_lock_irq(&css_set_lock);
+		css->cgroup = dcgrp;
 		WARN_ON(!list_empty(&dcgrp->e_csets[ss->id]));
 		list_for_each_entry_safe(cset, cset_pos, &scgrp->e_csets[ss->id],
 					 e_cset_node[ss->id]) {
@@ -1922,6 +1925,7 @@ enum cgroup2_param {
 	Opt_memory_localevents,
 	Opt_memory_recursiveprot,
 	Opt_memory_hugetlb_accounting,
+	Opt_pids_localevents,
 	nr__cgroup2_params
 };
 
@@ -1931,6 +1935,7 @@ static const struct fs_parameter_spec cgroup2_fs_parameters[] = {
 	fsparam_flag("memory_localevents",	Opt_memory_localevents),
 	fsparam_flag("memory_recursiveprot",	Opt_memory_recursiveprot),
 	fsparam_flag("memory_hugetlb_accounting", Opt_memory_hugetlb_accounting),
+	fsparam_flag("pids_localevents",	Opt_pids_localevents),
 	{}
 };
 
@@ -1960,6 +1965,9 @@ static int cgroup2_parse_param(struct fs_context *fc, struct fs_parameter *param
 	case Opt_memory_hugetlb_accounting:
 		ctx->flags |= CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;
 		return 0;
+	case Opt_pids_localevents:
+		ctx->flags |= CGRP_ROOT_PIDS_LOCAL_EVENTS;
+		return 0;
 	}
 	return -EINVAL;
 }
@@ -1989,6 +1997,11 @@ static void apply_cgroup_root_flags(unsigned int root_flags)
 			cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;
 		else
 			cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;
+
+		if (root_flags & CGRP_ROOT_PIDS_LOCAL_EVENTS)
+			cgrp_dfl_root.flags |= CGRP_ROOT_PIDS_LOCAL_EVENTS;
+		else
+			cgrp_dfl_root.flags &= ~CGRP_ROOT_PIDS_LOCAL_EVENTS;
 	}
 }
 
@@ -2004,6 +2017,8 @@ static int cgroup_show_options(struct seq_file *seq, struct kernfs_root *kf_root
 		seq_puts(seq, ",memory_recursiveprot");
 	if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING)
 		seq_puts(seq, ",memory_hugetlb_accounting");
+	if (cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS)
+		seq_puts(seq, ",pids_localevents");
 	return 0;
 }
 
@@ -6686,8 +6701,10 @@ void cgroup_exit(struct task_struct *tsk)
 	WARN_ON_ONCE(list_empty(&tsk->cg_list));
 	cset = task_css_set(tsk);
 	css_set_move_task(tsk, cset, NULL, false);
-	list_add_tail(&tsk->cg_list, &cset->dying_tasks);
 	cset->nr_tasks--;
+	/* matches the signal->live check in css_task_iter_advance() */
+	if (thread_group_leader(tsk) && atomic_read(&tsk->signal->live))
+		list_add_tail(&tsk->cg_list, &cset->dying_tasks);
 
 	if (dl_task(tsk))
 		dec_dl_tasks_cs(tsk);
@@ -6714,10 +6731,12 @@ void cgroup_release(struct task_struct *task)
 		ss->release(task);
 	} while_each_subsys_mask();
 
-	spin_lock_irq(&css_set_lock);
-	css_set_skip_task_iters(task_css_set(task), task);
-	list_del_init(&task->cg_list);
-	spin_unlock_irq(&css_set_lock);
+	if (!list_empty(&task->cg_list)) {
+		spin_lock_irq(&css_set_lock);
+		css_set_skip_task_iters(task_css_set(task), task);
+		list_del_init(&task->cg_list);
+		spin_unlock_irq(&css_set_lock);
+	}
 }
 
 void cgroup_free(struct task_struct *task)
@@ -7062,7 +7081,8 @@ static ssize_t features_show(struct kobject *kobj, struct kobj_attribute *attr,
 			"favordynmods\n"
 			"memory_localevents\n"
 			"memory_recursiveprot\n"
-			"memory_hugetlb_accounting\n");
+			"memory_hugetlb_accounting\n"
+			"pids_localevents\n");
 }
 static struct kobj_attribute cgroup_features_attr = __ATTR_RO(features);
 

kernel/cgroup/misc.c

@@ -121,6 +121,30 @@ static void misc_cg_cancel_charge(enum misc_res_type type, struct misc_cg *cg,
 		  misc_res_name[type]);
 }
 
+static void misc_cg_update_watermark(struct misc_res *res, u64 new_usage)
+{
+	u64 old;
+
+	while (true) {
+		old = atomic64_read(&res->watermark);
+		if (new_usage <= old)
+			break;
+		if (atomic64_cmpxchg(&res->watermark, old, new_usage) == old)
+			break;
+	}
+}
+
+static void misc_cg_event(enum misc_res_type type, struct misc_cg *cg)
+{
+	atomic64_inc(&cg->res[type].events_local);
+	cgroup_file_notify(&cg->events_local_file);
+
+	for (; parent_misc(cg); cg = parent_misc(cg)) {
+		atomic64_inc(&cg->res[type].events);
+		cgroup_file_notify(&cg->events_file);
+	}
+}
+
 /**
  * misc_cg_try_charge() - Try charging the misc cgroup.
  * @type: Misc res type to charge.
@@ -159,14 +183,12 @@ int misc_cg_try_charge(enum misc_res_type type, struct misc_cg *cg, u64 amount)
 			ret = -EBUSY;
 			goto err_charge;
 		}
+		misc_cg_update_watermark(res, new_usage);
 	}
 	return 0;
 
 err_charge:
-	for (j = i; j; j = parent_misc(j)) {
-		atomic64_inc(&j->res[type].events);
-		cgroup_file_notify(&j->events_file);
-	}
+	misc_cg_event(type, i);
 
 	for (j = cg; j != i; j = parent_misc(j))
 		misc_cg_cancel_charge(type, j, amount);
@@ -307,6 +329,29 @@ static int misc_cg_current_show(struct seq_file *sf, void *v)
 	return 0;
 }
 
+/**
+ * misc_cg_peak_show() - Show the peak usage of the misc cgroup.
+ * @sf: Interface file
+ * @v: Arguments passed
+ *
+ * Context: Any context.
+ * Return: 0 to denote successful print.
+ */
+static int misc_cg_peak_show(struct seq_file *sf, void *v)
+{
+	int i;
+	u64 watermark;
+	struct misc_cg *cg = css_misc(seq_css(sf));
+
+	for (i = 0; i < MISC_CG_RES_TYPES; i++) {
+		watermark = atomic64_read(&cg->res[i].watermark);
+		if (READ_ONCE(misc_res_capacity[i]) || watermark)
+			seq_printf(sf, "%s %llu\n", misc_res_name[i], watermark);
+	}
+
+	return 0;
+}
+
 /**
  * misc_cg_capacity_show() - Show the total capacity of misc res on the host.
  * @sf: Interface file
@@ -331,20 +376,33 @@ static int misc_cg_capacity_show(struct seq_file *sf, void *v)
 	return 0;
 }
 
-static int misc_events_show(struct seq_file *sf, void *v)
+static int __misc_events_show(struct seq_file *sf, bool local)
 {
 	struct misc_cg *cg = css_misc(seq_css(sf));
 	u64 events;
 	int i;
 
 	for (i = 0; i < MISC_CG_RES_TYPES; i++) {
-		events = atomic64_read(&cg->res[i].events);
+		if (local)
+			events = atomic64_read(&cg->res[i].events_local);
+		else
+			events = atomic64_read(&cg->res[i].events);
 		if (READ_ONCE(misc_res_capacity[i]) || events)
 			seq_printf(sf, "%s.max %llu\n", misc_res_name[i], events);
 	}
 	return 0;
 }
 
+static int misc_events_show(struct seq_file *sf, void *v)
+{
+	return __misc_events_show(sf, false);
+}
+
+static int misc_events_local_show(struct seq_file *sf, void *v)
+{
+	return __misc_events_show(sf, true);
+}
+
 /* Misc cgroup interface files */
 static struct cftype misc_cg_files[] = {
 	{
@@ -357,6 +415,10 @@ static struct cftype misc_cg_files[] = {
 		.name = "current",
 		.seq_show = misc_cg_current_show,
 	},
+	{
+		.name = "peak",
+		.seq_show = misc_cg_peak_show,
+	},
 	{
 		.name = "capacity",
 		.seq_show = misc_cg_capacity_show,
@@ -368,6 +430,12 @@ static struct cftype misc_cg_files[] = {
 		.file_offset = offsetof(struct misc_cg, events_file),
 		.seq_show = misc_events_show,
 	},
+	{
+		.name = "events.local",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.file_offset = offsetof(struct misc_cg, events_local_file),
+		.seq_show = misc_events_local_show,
+	},
 	{}
 };
 

kernel/cgroup/pids.c

@@ -38,6 +38,14 @@
 #define PIDS_MAX (PID_MAX_LIMIT + 1ULL)
 #define PIDS_MAX_STR "max"
 
+enum pidcg_event {
+	/* Fork failed in subtree because this pids_cgroup limit was hit. */
+	PIDCG_MAX,
+	/* Fork failed in this pids_cgroup because ancestor limit was hit. */
+	PIDCG_FORKFAIL,
+	NR_PIDCG_EVENTS,
+};
+
 struct pids_cgroup {
 	struct cgroup_subsys_state	css;
 
@@ -49,11 +57,12 @@ struct pids_cgroup {
 	atomic64_t			limit;
 	int64_t				watermark;
 
-	/* Handle for "pids.events" */
+	/* Handles for pids.events[.local] */
 	struct cgroup_file		events_file;
+	struct cgroup_file		events_local_file;
 
-	/* Number of times fork failed because limit was hit. */
-	atomic64_t			events_limit;
+	atomic64_t			events[NR_PIDCG_EVENTS];
+	atomic64_t			events_local[NR_PIDCG_EVENTS];
 };
 
 static struct pids_cgroup *css_pids(struct cgroup_subsys_state *css)
@@ -148,12 +157,13 @@ static void pids_charge(struct pids_cgroup *pids, int num)
  * pids_try_charge - hierarchically try to charge the pid count
  * @pids: the pid cgroup state
  * @num: the number of pids to charge
+ * @fail: storage of pid cgroup causing the fail
  *
  * This function follows the set limit. It will fail if the charge would cause
  * the new value to exceed the hierarchical limit. Returns 0 if the charge
  * succeeded, otherwise -EAGAIN.
  */
-static int pids_try_charge(struct pids_cgroup *pids, int num)
+static int pids_try_charge(struct pids_cgroup *pids, int num, struct pids_cgroup **fail)
 {
 	struct pids_cgroup *p, *q;
 
@@ -166,9 +176,10 @@ static int pids_try_charge(struct pids_cgroup *pids, int num)
 		 * p->limit is %PIDS_MAX then we know that this test will never
 		 * fail.
 		 */
-		if (new > limit)
+		if (new > limit) {
+			*fail = p;
 			goto revert;
-
+		}
 		/*
 		 * Not technically accurate if we go over limit somewhere up
 		 * the hierarchy, but that's tolerable for the watermark.
@@ -229,6 +240,36 @@ static void pids_cancel_attach(struct cgroup_taskset *tset)
 	}
 }
 
+static void pids_event(struct pids_cgroup *pids_forking,
+		       struct pids_cgroup *pids_over_limit)
+{
+	struct pids_cgroup *p = pids_forking;
+	bool limit = false;
+
+	/* Only log the first time limit is hit. */
+	if (atomic64_inc_return(&p->events_local[PIDCG_FORKFAIL]) == 1) {
+		pr_info("cgroup: fork rejected by pids controller in ");
+		pr_cont_cgroup_path(p->css.cgroup);
+		pr_cont("\n");
+	}
+	cgroup_file_notify(&p->events_local_file);
+	if (!cgroup_subsys_on_dfl(pids_cgrp_subsys) ||
+	    cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS)
+		return;
+
+	for (; parent_pids(p); p = parent_pids(p)) {
+		if (p == pids_over_limit) {
+			limit = true;
+			atomic64_inc(&p->events_local[PIDCG_MAX]);
+			cgroup_file_notify(&p->events_local_file);
+		}
+		if (limit)
+			atomic64_inc(&p->events[PIDCG_MAX]);
+
+		cgroup_file_notify(&p->events_file);
+	}
+}
+
 /*
  * task_css_check(true) in pids_can_fork() and pids_cancel_fork() relies
  * on cgroup_threadgroup_change_begin() held by the copy_process().
@@ -236,7 +277,7 @@ static void pids_cancel_attach(struct cgroup_taskset *tset)
 static int pids_can_fork(struct task_struct *task, struct css_set *cset)
 {
 	struct cgroup_subsys_state *css;
-	struct pids_cgroup *pids;
+	struct pids_cgroup *pids, *pids_over_limit;
 	int err;
 
 	if (cset)
@@ -244,16 +285,10 @@ static int pids_can_fork(struct task_struct *task, struct css_set *cset)
 	else
 		css = task_css_check(current, pids_cgrp_id, true);
 	pids = css_pids(css);
-	err = pids_try_charge(pids, 1);
-	if (err) {
-		/* Only log the first time events_limit is incremented. */
-		if (atomic64_inc_return(&pids->events_limit) == 1) {
-			pr_info("cgroup: fork rejected by pids controller in ");
-			pr_cont_cgroup_path(css->cgroup);
-			pr_cont("\n");
-		}
-		cgroup_file_notify(&pids->events_file);
-	}
+	err = pids_try_charge(pids, 1, &pids_over_limit);
+	if (err)
+		pids_event(pids, pids_over_limit);
+
 	return err;
 }
 
@@ -337,15 +372,68 @@ static s64 pids_peak_read(struct cgroup_subsys_state *css,
 	return READ_ONCE(pids->watermark);
 }
 
-static int pids_events_show(struct seq_file *sf, void *v)
+static int __pids_events_show(struct seq_file *sf, bool local)
 {
 	struct pids_cgroup *pids = css_pids(seq_css(sf));
+	enum pidcg_event pe = PIDCG_MAX;
+	atomic64_t *events;
+
+	if (!cgroup_subsys_on_dfl(pids_cgrp_subsys) ||
+	    cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS) {
+		pe = PIDCG_FORKFAIL;
+		local = true;
+	}
+	events = local ? pids->events_local : pids->events;
+
+	seq_printf(sf, "max %lld\n", (s64)atomic64_read(&events[pe]));
+	return 0;
+}
 
-	seq_printf(sf, "max %lld\n", (s64)atomic64_read(&pids->events_limit));
+static int pids_events_show(struct seq_file *sf, void *v)
+{
+	__pids_events_show(sf, false);
+	return 0;
+}
+
+static int pids_events_local_show(struct seq_file *sf, void *v)
+{
+	__pids_events_show(sf, true);
 	return 0;
 }
 
 static struct cftype pids_files[] = {
+	{
+		.name = "max",
+		.write = pids_max_write,
+		.seq_show = pids_max_show,
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	{
+		.name = "current",
+		.read_s64 = pids_current_read,
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	{
+		.name = "peak",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.read_s64 = pids_peak_read,
+	},
+	{
+		.name = "events",
+		.seq_show = pids_events_show,
+		.file_offset = offsetof(struct pids_cgroup, events_file),
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	{
+		.name = "events.local",
+		.seq_show = pids_events_local_show,
+		.file_offset = offsetof(struct pids_cgroup, events_local_file),
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	{ }	/* terminate */
+};
+
+static struct cftype pids_files_legacy[] = {
 	{
 		.name = "max",
 		.write = pids_max_write,
@@ -371,6 +459,7 @@ static struct cftype pids_files[] = {
 	{ }	/* terminate */
 };
 
+
 struct cgroup_subsys pids_cgrp_subsys = {
 	.css_alloc	= pids_css_alloc,
 	.css_free	= pids_css_free,
@@ -379,7 +468,7 @@ struct cgroup_subsys pids_cgrp_subsys = {
 	.can_fork	= pids_can_fork,
 	.cancel_fork	= pids_cancel_fork,
 	.release	= pids_release,
-	.legacy_cftypes	= pids_files,
+	.legacy_cftypes = pids_files_legacy,
 	.dfl_cftypes	= pids_files,
 	.threaded	= true,
 };

kernel/cgroup/rstat.c

@@ -594,49 +594,46 @@ static void root_cgroup_cputime(struct cgroup_base_stat *bstat)
 	}
 }
 
+
+static void cgroup_force_idle_show(struct seq_file *seq, struct cgroup_base_stat *bstat)
+{
+#ifdef CONFIG_SCHED_CORE
+	u64 forceidle_time = bstat->forceidle_sum;
+
+	do_div(forceidle_time, NSEC_PER_USEC);
+	seq_printf(seq, "core_sched.force_idle_usec %llu\n", forceidle_time);
+#endif
+}
+
 void cgroup_base_stat_cputime_show(struct seq_file *seq)
 {
 	struct cgroup *cgrp = seq_css(seq)->cgroup;
 	u64 usage, utime, stime;
-	struct cgroup_base_stat bstat;
-#ifdef CONFIG_SCHED_CORE
-	u64 forceidle_time;
-#endif
 
 	if (cgroup_parent(cgrp)) {
 		cgroup_rstat_flush_hold(cgrp);
 		usage = cgrp->bstat.cputime.sum_exec_runtime;
 		cputime_adjust(&cgrp->bstat.cputime, &cgrp->prev_cputime,
 			       &utime, &stime);
-#ifdef CONFIG_SCHED_CORE
-		forceidle_time = cgrp->bstat.forceidle_sum;
-#endif
 		cgroup_rstat_flush_release(cgrp);
 	} else {
-		root_cgroup_cputime(&bstat);
-		usage = bstat.cputime.sum_exec_runtime;
-		utime = bstat.cputime.utime;
-		stime = bstat.cputime.stime;
-#ifdef CONFIG_SCHED_CORE
-		forceidle_time = bstat.forceidle_sum;
-#endif
+		/* cgrp->bstat of root is not actually used, reuse it */
+		root_cgroup_cputime(&cgrp->bstat);
+		usage = cgrp->bstat.cputime.sum_exec_runtime;
+		utime = cgrp->bstat.cputime.utime;
+		stime = cgrp->bstat.cputime.stime;
 	}
 
 	do_div(usage, NSEC_PER_USEC);
 	do_div(utime, NSEC_PER_USEC);
 	do_div(stime, NSEC_PER_USEC);
-#ifdef CONFIG_SCHED_CORE
-	do_div(forceidle_time, NSEC_PER_USEC);
-#endif
 
 	seq_printf(seq, "usage_usec %llu\n"
 		   "user_usec %llu\n"
 		   "system_usec %llu\n",
 		   usage, utime, stime);
 
-#ifdef CONFIG_SCHED_CORE
-	seq_printf(seq, "core_sched.force_idle_usec %llu\n", forceidle_time);
-#endif
+	cgroup_force_idle_show(seq, &cgrp->bstat);
 }
 
 /* Add bpf kfuncs for cgroup_rstat_updated() and cgroup_rstat_flush() */

tools/testing/selftests/cgroup/.gitignore

 # SPDX-License-Identifier: GPL-2.0-only
-test_memcontrol
 test_core
-test_freezer
-test_kmem
-test_kill
 test_cpu
 test_cpuset
-test_zswap
+test_freezer
 test_hugetlb_memcg
+test_kill
+test_kmem
+test_memcontrol
+test_pids
+test_zswap
 wait_inotify

tools/testing/selftests/cgroup/Makefile

@@ -6,26 +6,29 @@ all: ${HELPER_PROGS}
 TEST_FILES     := with_stress.sh
 TEST_PROGS     := test_stress.sh test_cpuset_prs.sh test_cpuset_v1_hp.sh
 TEST_GEN_FILES := wait_inotify
-TEST_GEN_PROGS = test_memcontrol
-TEST_GEN_PROGS += test_kmem
-TEST_GEN_PROGS += test_core
-TEST_GEN_PROGS += test_freezer
-TEST_GEN_PROGS += test_kill
+# Keep the lists lexicographically sorted
+TEST_GEN_PROGS  = test_core
 TEST_GEN_PROGS += test_cpu
 TEST_GEN_PROGS += test_cpuset
-TEST_GEN_PROGS += test_zswap
+TEST_GEN_PROGS += test_freezer
 TEST_GEN_PROGS += test_hugetlb_memcg
+TEST_GEN_PROGS += test_kill
+TEST_GEN_PROGS += test_kmem
+TEST_GEN_PROGS += test_memcontrol
+TEST_GEN_PROGS += test_pids
+TEST_GEN_PROGS += test_zswap
 
 LOCAL_HDRS += $(selfdir)/clone3/clone3_selftests.h $(selfdir)/pidfd/pidfd.h
 
 include ../lib.mk
 
-$(OUTPUT)/test_memcontrol: cgroup_util.c
-$(OUTPUT)/test_kmem: cgroup_util.c
 $(OUTPUT)/test_core: cgroup_util.c
-$(OUTPUT)/test_freezer: cgroup_util.c
-$(OUTPUT)/test_kill: cgroup_util.c
 $(OUTPUT)/test_cpu: cgroup_util.c
 $(OUTPUT)/test_cpuset: cgroup_util.c
-$(OUTPUT)/test_zswap: cgroup_util.c
+$(OUTPUT)/test_freezer: cgroup_util.c
 $(OUTPUT)/test_hugetlb_memcg: cgroup_util.c
+$(OUTPUT)/test_kill: cgroup_util.c
+$(OUTPUT)/test_kmem: cgroup_util.c
+$(OUTPUT)/test_memcontrol: cgroup_util.c
+$(OUTPUT)/test_pids: cgroup_util.c
+$(OUTPUT)/test_zswap: cgroup_util.c

tools/testing/selftests/cgroup/test_cpuset_prs.sh

@@ -28,6 +28,14 @@ CPULIST=$(cat $CGROUP2/cpuset.cpus.effective)
 NR_CPUS=$(lscpu | grep "^CPU(s):" | sed -e "s/.*:[[:space:]]*//")
 [[ $NR_CPUS -lt 8 ]] && skip_test "Test needs at least 8 cpus available!"
 
+# Check to see if /dev/console exists and is writable
+if [[ -c /dev/console && -w /dev/console ]]
+then
+	CONSOLE=/dev/console
+else
+	CONSOLE=/dev/null
+fi
+
 # Set verbose flag and delay factor
 PROG=$1
 VERBOSE=0
@@ -103,8 +111,8 @@ console_msg()
 {
 	MSG=$1
 	echo "$MSG"
-	echo "" > /dev/console
-	echo "$MSG" > /dev/console
+	echo "" > $CONSOLE
+	echo "$MSG" > $CONSOLE
 	pause 0.01
 }
 
@@ -161,6 +169,14 @@ test_add_proc()
 #  T    = put a task into cgroup
 #  O<c>=<v> = Write <v> to CPU online file of <c>
 #
+# ECPUs    - effective CPUs of cpusets
+# Pstate   - partition root state
+# ISOLCPUS - isolated CPUs (<icpus>[,<icpus2>])
+#
+# Note that if there are 2 fields in ISOLCPUS, the first one is for
+# sched-debug matching which includes offline CPUs and single-CPU partitions
+# while the second one is for matching cpuset.cpus.isolated.
+#
 SETUP_A123_PARTITIONS="C1-3:P1:S+ C2-3:P1:S+ C3:P1"
 TEST_MATRIX=(
 	#  old-A1 old-A2 old-A3 old-B1 new-A1 new-A2 new-A3 new-B1 fail ECPUs Pstate ISOLCPUS
@@ -220,23 +236,29 @@ TEST_MATRIX=(
 	" C0-3:S+ C1-3:S+ C2-3     .    X2-3  X2-3:P2   .      .     0 A1:0-1,A2:2-3,A3:2-3 A1:P0,A2:P2 2-3"
 	" C0-3:S+ C1-3:S+ C2-3     .    X2-3   X3:P2    .      .     0 A1:0-2,A2:3,A3:3 A1:P0,A2:P2 3"
 	" C0-3:S+ C1-3:S+ C2-3     .    X2-3   X2-3  X2-3:P2   .     0 A1:0-1,A2:1,A3:2-3 A1:P0,A3:P2 2-3"
-	" C0-3:S+ C1-3:S+ C2-3     .    X2-3   X2-3 X2-3:P2:C3 .     0 A1:0-2,A2:1-2,A3:3 A1:P0,A3:P2 3"
+	" C0-3:S+ C1-3:S+ C2-3     .    X2-3   X2-3 X2-3:P2:C3 .     0 A1:0-1,A2:1,A3:2-3 A1:P0,A3:P2 2-3"
 	" C0-3:S+ C1-3:S+ C2-3   C2-3     .      .      .      P2    0 A1:0-3,A2:1-3,A3:2-3,B1:2-3 A1:P0,A3:P0,B1:P-2"
 	" C0-3:S+ C1-3:S+ C2-3   C4-5     .      .      .      P2    0 B1:4-5 B1:P2 4-5"
 	" C0-3:S+ C1-3:S+ C2-3    C4    X2-3   X2-3  X2-3:P2   P2    0 A3:2-3,B1:4 A3:P2,B1:P2 2-4"
 	" C0-3:S+ C1-3:S+ C2-3    C4    X2-3   X2-3 X2-3:P2:C1-3 P2  0 A3:2-3,B1:4 A3:P2,B1:P2 2-4"
 	" C0-3:S+ C1-3:S+ C2-3    C4    X1-3  X1-3:P2   P2     .     0 A2:1,A3:2-3 A2:P2,A3:P2 1-3"
 	" C0-3:S+ C1-3:S+ C2-3    C4    X2-3   X2-3  X2-3:P2 P2:C4-5 0 A3:2-3,B1:4-5 A3:P2,B1:P2 2-5"
+	" C4:X0-3:S+ X1-3:S+ X2-3  .      .      P2     .      .     0 A1:4,A2:1-3,A3:1-3 A2:P2 1-3"
+	" C4:X0-3:S+ X1-3:S+ X2-3  .      .      .      P2     .     0 A1:4,A2:4,A3:2-3 A3:P2 2-3"
 
 	# Nested remote/local partition tests
 	" C0-3:S+ C1-3:S+ C2-3   C4-5   X2-3  X2-3:P1   P2     P1    0 A1:0-1,A2:,A3:2-3,B1:4-5 \
 								       A1:P0,A2:P1,A3:P2,B1:P1 2-3"
 	" C0-3:S+ C1-3:S+ C2-3    C4    X2-3  X2-3:P1   P2     P1    0 A1:0-1,A2:,A3:2-3,B1:4 \
 								       A1:P0,A2:P1,A3:P2,B1:P1 2-4,2-3"
+	" C0-3:S+ C1-3:S+ C2-3    C4    X2-3  X2-3:P1    .     P1    0 A1:0-1,A2:2-3,A3:2-3,B1:4 \
+								       A1:P0,A2:P1,A3:P0,B1:P1"
 	" C0-3:S+ C1-3:S+  C3     C4    X2-3  X2-3:P1   P2     P1    0 A1:0-1,A2:2,A3:3,B1:4 \
 								       A1:P0,A2:P1,A3:P2,B1:P1 2-4,3"
 	" C0-4:S+ C1-4:S+ C2-4     .    X2-4  X2-4:P2  X4:P1    .    0 A1:0-1,A2:2-3,A3:4 \
 								       A1:P0,A2:P2,A3:P1 2-4,2-3"
+	" C0-4:S+ C1-4:S+ C2-4     .    X2-4  X2-4:P2 X3-4:P1   .    0 A1:0-1,A2:2,A3:3-4 \
+								       A1:P0,A2:P2,A3:P1 2"
 	" C0-4:X2-4:S+ C1-4:X2-4:S+:P2 C2-4:X4:P1 \
 				   .      .      X5      .      .    0 A1:0-4,A2:1-4,A3:2-4 \
 								       A1:P0,A2:P-2,A3:P-1"
@@ -262,8 +284,8 @@ TEST_MATRIX=(
 			    .      .    X2-3    P2      .      .     0 A1:0-2,A2:3,XA2:3 A2:P2 3"
 
 	# Invalid to valid local partition direct transition tests
-	" C1-3:S+:P2 C2-3:X1:P2 .  .      .      .      .      .     0 A1:1-3,XA1:1-3,A2:2-3:XA2: A1:P2,A2:P-2 1-3"
-	" C1-3:S+:P2 C2-3:X1:P2 .  .      .    X3:P2    .      .     0 A1:1-2,XA1:1-3,A2:3:XA2:3 A1:P2,A2:P2 1-3"
+	" C1-3:S+:P2 X4:P2  .      .      .      .      .      .     0 A1:1-3,XA1:1-3,A2:1-3:XA2: A1:P2,A2:P-2 1-3"
+	" C1-3:S+:P2 X4:P2  .      .      .    X3:P2    .      .     0 A1:1-2,XA1:1-3,A2:3:XA2:3 A1:P2,A2:P2 1-3"
 	"  C0-3:P2   .      .    C4-6   C0-4     .      .      .     0 A1:0-4,B1:4-6 A1:P-2,B1:P0"
 	"  C0-3:P2   .      .    C4-6 C0-4:C0-3  .      .      .     0 A1:0-3,B1:4-6 A1:P2,B1:P0 0-3"
 	"  C0-3:P2   .      .  C3-5:C4-5  .      .      .      .     0 A1:0-3,B1:4-5 A1:P2,B1:P0 0-3"
@@ -274,21 +296,18 @@ TEST_MATRIX=(
 	" C0-3:X1-3:S+:P2 C1-3:X2-3:S+:P2 C2-3:X3:P2 \
 				   .      .     X4      .      .     0 A1:1-3,A2:1-3,A3:2-3,XA2:,XA3: A1:P2,A2:P-2,A3:P-2 1-3"
 	" C0-3:X1-3:S+:P2 C1-3:X2-3:S+:P2 C2-3:X3:P2 \
-				   .      .     C4      .      .     0 A1:1-3,A2:1-3,A3:2-3,XA2:,XA3: A1:P2,A2:P-2,A3:P-2 1-3"
+				   .      .    C4:X     .      .     0 A1:1-3,A2:1-3,A3:2-3,XA2:,XA3: A1:P2,A2:P-2,A3:P-2 1-3"
 	# Local partition CPU change tests
 	" C0-5:S+:P2 C4-5:S+:P1 .  .      .    C3-5     .      .     0 A1:0-2,A2:3-5 A1:P2,A2:P1 0-2"
 	" C0-5:S+:P2 C4-5:S+:P1 .  .    C1-5     .      .      .     0 A1:1-3,A2:4-5 A1:P2,A2:P1 1-3"
 
 	# cpus_allowed/exclusive_cpus update tests
 	" C0-3:X2-3:S+ C1-3:X2-3:S+ C2-3:X2-3 \
-				   .     C4      .      P2     .     0 A1:4,A2:4,XA2:,XA3:,A3:4 \
+				   .    X:C4     .      P2     .     0 A1:4,A2:4,XA2:,XA3:,A3:4 \
 								       A1:P0,A3:P-2"
 	" C0-3:X2-3:S+ C1-3:X2-3:S+ C2-3:X2-3 \
 				   .     X1      .      P2     .     0 A1:0-3,A2:1-3,XA1:1,XA2:,XA3:,A3:2-3 \
 								       A1:P0,A3:P-2"
-	" C0-3:X2-3:S+ C1-3:X2-3:S+ C2-3:X2-3 \
-				   .      .     C3      P2     .     0 A1:0-2,A2:0-2,XA2:3,XA3:3,A3:3 \
-								       A1:P0,A3:P2 3"
 	" C0-3:X2-3:S+ C1-3:X2-3:S+ C2-3:X2-3 \
 				   .      .     X3      P2     .     0 A1:0-2,A2:1-2,XA2:3,XA3:3,A3:3 \
 								       A1:P0,A3:P2 3"
@@ -296,10 +315,7 @@ TEST_MATRIX=(
 				   .      .     X3      .      .     0 A1:0-3,A2:1-3,XA2:3,XA3:3,A3:2-3 \
 								       A1:P0,A3:P-2"
 	" C0-3:X2-3:S+ C1-3:X2-3:S+ C2-3:X2-3:P2 \
-				   .      .     C3      .      .     0 A1:0-3,A2:3,XA2:3,XA3:3,A3:3 \
-								       A1:P0,A3:P-2"
-	" C0-3:X2-3:S+ C1-3:X2-3:S+ C2-3:X2-3:P2 \
-				   .     C4      .      .      .     0 A1:4,A2:4,A3:4,XA1:,XA2:,XA3 \
+				   .     X4      .      .      .     0 A1:0-3,A2:1-3,A3:2-3,XA1:4,XA2:,XA3 \
 								       A1:P0,A3:P-2"
 
 	#  old-A1 old-A2 old-A3 old-B1 new-A1 new-A2 new-A3 new-B1 fail ECPUs Pstate ISOLCPUS
@@ -346,6 +362,9 @@ TEST_MATRIX=(
 	"  C0-1:P1   .      .  P1:C2-3  C0-2     .      .      .     0 A1:0-2,B1:2-3 A1:P-1,B1:P-1"
 	"   C0-1     .      .  P1:C2-3  C0-2     .      .      .     0 A1:0-2,B1:2-3 A1:P0,B1:P-1"
 
+	# cpuset.cpus can overlap with sibling cpuset.cpus.exclusive but not subsumed by it
+	"   C0-3     .      .    C4-5     X5     .      .      .     0 A1:0-3,B1:4-5"
+
 	#  old-A1 old-A2 old-A3 old-B1 new-A1 new-A2 new-A3 new-B1 fail ECPUs Pstate ISOLCPUS
 	#  ------ ------ ------ ------ ------ ------ ------ ------ ---- ----- ------ --------
 	# Failure cases:
@@ -355,6 +374,9 @@ TEST_MATRIX=(
 
 	# Changes to cpuset.cpus.exclusive that violate exclusivity rule is rejected
 	"   C0-3     .      .    C4-5   X0-3     .      .     X3-5   1 A1:0-3,B1:4-5"
+
+	# cpuset.cpus cannot be a subset of sibling cpuset.cpus.exclusive
+	"   C0-3     .      .    C4-5   X3-5     .      .      .     1 A1:0-3,B1:4-5"
 )
 
 #
@@ -556,14 +578,15 @@ check_cgroup_states()
 	do
 		set -- $(echo $CHK | sed -e "s/:/ /g")
 		CGRP=$1
+		CGRP_DIR=$CGRP
 		STATE=$2
 		FILE=
 		EVAL=$(expr substr $STATE 2 2)
-		[[ $CGRP = A2 ]] && CGRP=A1/A2
-		[[ $CGRP = A3 ]] && CGRP=A1/A2/A3
+		[[ $CGRP = A2 ]] && CGRP_DIR=A1/A2
+		[[ $CGRP = A3 ]] && CGRP_DIR=A1/A2/A3
 
 		case $STATE in
-			P*) FILE=$CGRP/cpuset.cpus.partition
+			P*) FILE=$CGRP_DIR/cpuset.cpus.partition
 			    ;;
 			*)  echo "Unknown state: $STATE!"
 			    exit 1
@@ -587,6 +610,16 @@ check_cgroup_states()
 				;;
 		esac
 		[[ $EVAL != $VAL ]] && return 1
+
+		#
+		# For root partition, dump sched-domains info to console if
+		# verbose mode set for manual comparison with sched debug info.
+		#
+		[[ $VAL -eq 1 && $VERBOSE -gt 0 ]] && {
+			DOMS=$(cat $CGRP_DIR/cpuset.cpus.effective)
+			[[ -n "$DOMS" ]] &&
+				echo " [$CGRP] sched-domain: $DOMS" > $CONSOLE
+		}
 	done
 	return 0
 }
@@ -694,9 +727,9 @@ null_isolcpus_check()
 	[[ $VERBOSE -gt 0 ]] || return 0
 	# Retry a few times before printing error
 	RETRY=0
-	while [[ $RETRY -lt 5 ]]
+	while [[ $RETRY -lt 8 ]]
 	do
-		pause 0.01
+		pause 0.02
 		check_isolcpus "."
 		[[ $? -eq 0 ]] && return 0
 		((RETRY++))
@@ -726,7 +759,7 @@ run_state_test()
 
 	while [[ $I -lt $CNT ]]
 	do
-		echo "Running test $I ..." > /dev/console
+		echo "Running test $I ..." > $CONSOLE
 		[[ $VERBOSE -gt 1 ]] && {
 			echo ""
 			eval echo \${$TEST[$I]}
@@ -783,7 +816,7 @@ run_state_test()
 		while [[ $NEWLIST != $CPULIST && $RETRY -lt 8 ]]
 		do
 			# Wait a bit longer & recheck a few times
-			pause 0.01
+			pause 0.02
 			((RETRY++))
 			NEWLIST=$(cat cpuset.cpus.effective)
 		done

tools/testing/selftests/cgroup/test_pids.c

+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+
+#include <errno.h>
+#include <linux/limits.h>
+#include <signal.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "../kselftest.h"
+#include "cgroup_util.h"
+
+static int run_success(const char *cgroup, void *arg)
+{
+	return 0;
+}
+
+static int run_pause(const char *cgroup, void *arg)
+{
+	return pause();
+}
+
+/*
+ * This test checks that pids.max prevents forking new children above the
+ * specified limit in the cgroup.
+ */
+static int test_pids_max(const char *root)
+{
+	int ret = KSFT_FAIL;
+	char *cg_pids;
+	int pid;
+
+	cg_pids = cg_name(root, "pids_test");
+	if (!cg_pids)
+		goto cleanup;
+
+	if (cg_create(cg_pids))
+		goto cleanup;
+
+	if (cg_read_strcmp(cg_pids, "pids.max", "max\n"))
+		goto cleanup;
+
+	if (cg_write(cg_pids, "pids.max", "2"))
+		goto cleanup;
+
+	if (cg_enter_current(cg_pids))
+		goto cleanup;
+
+	pid = cg_run_nowait(cg_pids, run_pause, NULL);
+	if (pid < 0)
+		goto cleanup;
+
+	if (cg_run_nowait(cg_pids, run_success, NULL) != -1 || errno != EAGAIN)
+		goto cleanup;
+
+	if (kill(pid, SIGINT))
+		goto cleanup;
+
+	ret = KSFT_PASS;
+
+cleanup:
+	cg_enter_current(root);
+	cg_destroy(cg_pids);
+	free(cg_pids);
+
+	return ret;
+}
+
+/*
+ * This test checks that pids.events are counted in cgroup associated with pids.max
+ */
+static int test_pids_events(const char *root)
+{
+	int ret = KSFT_FAIL;
+	char *cg_parent = NULL, *cg_child = NULL;
+	int pid;
+
+	cg_parent = cg_name(root, "pids_parent");
+	cg_child = cg_name(cg_parent, "pids_child");
+	if (!cg_parent || !cg_child)
+		goto cleanup;
+
+	if (cg_create(cg_parent))
+		goto cleanup;
+	if (cg_write(cg_parent, "cgroup.subtree_control", "+pids"))
+		goto cleanup;
+	if (cg_create(cg_child))
+		goto cleanup;
+
+	if (cg_write(cg_parent, "pids.max", "2"))
+		goto cleanup;
+
+	if (cg_read_strcmp(cg_child, "pids.max", "max\n"))
+		goto cleanup;
+
+	if (cg_enter_current(cg_child))
+		goto cleanup;
+
+	pid = cg_run_nowait(cg_child, run_pause, NULL);
+	if (pid < 0)
+		goto cleanup;
+
+	if (cg_run_nowait(cg_child, run_success, NULL) != -1 || errno != EAGAIN)
+		goto cleanup;
+
+	if (kill(pid, SIGINT))
+		goto cleanup;
+
+	if (cg_read_key_long(cg_child, "pids.events", "max ") != 0)
+		goto cleanup;
+	if (cg_read_key_long(cg_parent, "pids.events", "max ") != 1)
+		goto cleanup;
+
+
+	ret = KSFT_PASS;
+
+cleanup:
+	cg_enter_current(root);
+	if (cg_child)
+		cg_destroy(cg_child);
+	if (cg_parent)
+		cg_destroy(cg_parent);
+	free(cg_child);
+	free(cg_parent);
+
+	return ret;
+}
+
+
+
+#define T(x) { x, #x }
+struct pids_test {
+	int (*fn)(const char *root);
+	const char *name;
+} tests[] = {
+	T(test_pids_max),
+	T(test_pids_events),
+};
+#undef T
+
+int main(int argc, char **argv)
+{
+	char root[PATH_MAX];
+
+	ksft_print_header();
+	ksft_set_plan(ARRAY_SIZE(tests));
+	if (cg_find_unified_root(root, sizeof(root), NULL))
+		ksft_exit_skip("cgroup v2 isn't mounted\n");
+
+	/*
+	 * Check that pids controller is available:
+	 * pids is listed in cgroup.controllers
+	 */
+	if (cg_read_strstr(root, "cgroup.controllers", "pids"))
+		ksft_exit_skip("pids controller isn't available\n");
+
+	if (cg_read_strstr(root, "cgroup.subtree_control", "pids"))
+		if (cg_write(root, "cgroup.subtree_control", "+pids"))
+			ksft_exit_skip("Failed to set pids controller\n");
+
+	for (int 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:
+			ksft_test_result_fail("%s\n", tests[i].name);
+			break;
+		}
+	}
+
+	ksft_finished();
+}