Merge branch 'for-5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:
 "Nothing too interesting. This adds cpu controller selftests and there
  are a couple code cleanup patches"

* 'for-5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: remove the superfluous judgment
  cgroup: Make cgroup_debug static
  kseltest/cgroup: Make test_stress.sh work if run interactively
  kselftest/cgroup: fix test_stress.sh to use OUTPUT dir
  cgroup: Add config file to cgroup selftest suite
  cgroup: Add test_cpucg_max_nested() testcase
  cgroup: Add test_cpucg_max() testcase
  cgroup: Add test_cpucg_nested_weight_underprovisioned() testcase
  cgroup: Adding test_cpucg_nested_weight_overprovisioned() testcase
  cgroup: Add test_cpucg_weight_underprovisioned() testcase
  cgroup: Add test_cpucg_weight_overprovisioned() testcase
  cgroup: Add test_cpucg_stats() testcase to cgroup cpu selftests
  cgroup: Add new test_cpu.c test suite in cgroup selftests

kernel/cgroup/cgroup-internal.h

@@ -12,7 +12,6 @@
 #define TRACE_CGROUP_PATH_LEN 1024
 extern spinlock_t trace_cgroup_path_lock;
 extern char trace_cgroup_path[TRACE_CGROUP_PATH_LEN];
-extern bool cgroup_debug;
 extern void __init enable_debug_cgroup(void);
 
 /*

kernel/cgroup/cgroup.c

@@ -96,7 +96,7 @@ EXPORT_SYMBOL_GPL(css_set_lock);
 
 DEFINE_SPINLOCK(trace_cgroup_path_lock);
 char trace_cgroup_path[TRACE_CGROUP_PATH_LEN];
-bool cgroup_debug __read_mostly;
+static bool cgroup_debug __read_mostly;
 
 /*
  * Protects cgroup_idr and css_idr so that IDs can be released without
@@ -5685,7 +5685,7 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
 	css_clear_dir(&cgrp->self);
 	kernfs_remove(cgrp->kn);
 
-	if (parent && cgroup_is_threaded(cgrp))
+	if (cgroup_is_threaded(cgrp))
 		parent->nr_threaded_children--;
 
 	spin_lock_irq(&css_set_lock);

tools/testing/selftests/cgroup/.gitignore

@@ -4,3 +4,4 @@ test_core
 test_freezer
 test_kmem
 test_kill
+test_cpu

tools/testing/selftests/cgroup/Makefile

@@ -10,6 +10,7 @@ TEST_GEN_PROGS += test_kmem
 TEST_GEN_PROGS += test_core
 TEST_GEN_PROGS += test_freezer
 TEST_GEN_PROGS += test_kill
+TEST_GEN_PROGS += test_cpu
 
 LOCAL_HDRS += $(selfdir)/clone3/clone3_selftests.h $(selfdir)/pidfd/pidfd.h
 
@@ -20,3 +21,4 @@ $(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

tools/testing/selftests/cgroup/cgroup_util.c

@@ -190,6 +190,18 @@ int cg_write(const char *cgroup, const char *control, char *buf)
 	return -1;
 }
 
+int cg_write_numeric(const char *cgroup, const char *control, long value)
+{
+	char buf[64];
+	int ret;
+
+	ret = sprintf(buf, "%lu", value);
+	if (ret < 0)
+		return ret;
+
+	return cg_write(cgroup, control, buf);
+}
+
 int cg_find_unified_root(char *root, size_t len)
 {
 	char buf[10 * PAGE_SIZE];

tools/testing/selftests/cgroup/cgroup_util.h

@@ -8,6 +8,9 @@
 
 #define MB(x) (x << 20)
 
+#define USEC_PER_SEC	1000000L
+#define NSEC_PER_SEC	1000000000L
+
 /*
  * Checks if two given values differ by less than err% of their sum.
  */
@@ -32,6 +35,7 @@ extern long cg_read_long(const char *cgroup, const char *control);
 long cg_read_key_long(const char *cgroup, const char *control, const char *key);
 extern long cg_read_lc(const char *cgroup, const char *control);
 extern int cg_write(const char *cgroup, const char *control, char *buf);
+int cg_write_numeric(const char *cgroup, const char *control, long value);
 extern int cg_run(const char *cgroup,
 		  int (*fn)(const char *cgroup, void *arg),
 		  void *arg);

tools/testing/selftests/cgroup/config

+CONFIG_CGROUPS=y
+CONFIG_CGROUP_CPUACCT=y
+CONFIG_CGROUP_FREEZER=y
+CONFIG_CGROUP_SCHED=y
+CONFIG_MEMCG=y
+CONFIG_MEMCG_KMEM=y
+CONFIG_MEMCG_SWAP=y
+CONFIG_PAGE_COUNTER=y

tools/testing/selftests/cgroup/test_cpu.c

+// SPDX-License-Identifier: GPL-2.0
+
+#define _GNU_SOURCE
+#include <linux/limits.h>
+#include <sys/sysinfo.h>
+#include <sys/wait.h>
+#include <errno.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <time.h>
+
+#include "../kselftest.h"
+#include "cgroup_util.h"
+
+enum hog_clock_type {
+	// Count elapsed time using the CLOCK_PROCESS_CPUTIME_ID clock.
+	CPU_HOG_CLOCK_PROCESS,
+	// Count elapsed time using system wallclock time.
+	CPU_HOG_CLOCK_WALL,
+};
+
+struct cpu_hogger {
+	char *cgroup;
+	pid_t pid;
+	long usage;
+};
+
+struct cpu_hog_func_param {
+	int nprocs;
+	struct timespec ts;
+	enum hog_clock_type clock_type;
+};
+
+/*
+ * This test creates two nested cgroups with and without enabling
+ * the cpu controller.
+ */
+static int test_cpucg_subtree_control(const char *root)
+{
+	char *parent = NULL, *child = NULL, *parent2 = NULL, *child2 = NULL;
+	int ret = KSFT_FAIL;
+
+	// Create two nested cgroups with the cpu controller enabled.
+	parent = cg_name(root, "cpucg_test_0");
+	if (!parent)
+		goto cleanup;
+
+	if (cg_create(parent))
+		goto cleanup;
+
+	if (cg_write(parent, "cgroup.subtree_control", "+cpu"))
+		goto cleanup;
+
+	child = cg_name(parent, "cpucg_test_child");
+	if (!child)
+		goto cleanup;
+
+	if (cg_create(child))
+		goto cleanup;
+
+	if (cg_read_strstr(child, "cgroup.controllers", "cpu"))
+		goto cleanup;
+
+	// Create two nested cgroups without enabling the cpu controller.
+	parent2 = cg_name(root, "cpucg_test_1");
+	if (!parent2)
+		goto cleanup;
+
+	if (cg_create(parent2))
+		goto cleanup;
+
+	child2 = cg_name(parent2, "cpucg_test_child");
+	if (!child2)
+		goto cleanup;
+
+	if (cg_create(child2))
+		goto cleanup;
+
+	if (!cg_read_strstr(child2, "cgroup.controllers", "cpu"))
+		goto cleanup;
+
+	ret = KSFT_PASS;
+
+cleanup:
+	cg_destroy(child);
+	free(child);
+	cg_destroy(child2);
+	free(child2);
+	cg_destroy(parent);
+	free(parent);
+	cg_destroy(parent2);
+	free(parent2);
+
+	return ret;
+}
+
+static void *hog_cpu_thread_func(void *arg)
+{
+	while (1)
+		;
+
+	return NULL;
+}
+
+static struct timespec
+timespec_sub(const struct timespec *lhs, const struct timespec *rhs)
+{
+	struct timespec zero = {
+		.tv_sec = 0,
+		.tv_nsec = 0,
+	};
+	struct timespec ret;
+
+	if (lhs->tv_sec < rhs->tv_sec)
+		return zero;
+
+	ret.tv_sec = lhs->tv_sec - rhs->tv_sec;
+
+	if (lhs->tv_nsec < rhs->tv_nsec) {
+		if (ret.tv_sec == 0)
+			return zero;
+
+		ret.tv_sec--;
+		ret.tv_nsec = NSEC_PER_SEC - rhs->tv_nsec + lhs->tv_nsec;
+	} else
+		ret.tv_nsec = lhs->tv_nsec - rhs->tv_nsec;
+
+	return ret;
+}
+
+static int hog_cpus_timed(const char *cgroup, void *arg)
+{
+	const struct cpu_hog_func_param *param =
+		(struct cpu_hog_func_param *)arg;
+	struct timespec ts_run = param->ts;
+	struct timespec ts_remaining = ts_run;
+	struct timespec ts_start;
+	int i, ret;
+
+	ret = clock_gettime(CLOCK_MONOTONIC, &ts_start);
+	if (ret != 0)
+		return ret;
+
+	for (i = 0; i < param->nprocs; i++) {
+		pthread_t tid;
+
+		ret = pthread_create(&tid, NULL, &hog_cpu_thread_func, NULL);
+		if (ret != 0)
+			return ret;
+	}
+
+	while (ts_remaining.tv_sec > 0 || ts_remaining.tv_nsec > 0) {
+		struct timespec ts_total;
+
+		ret = nanosleep(&ts_remaining, NULL);
+		if (ret && errno != EINTR)
+			return ret;
+
+		if (param->clock_type == CPU_HOG_CLOCK_PROCESS) {
+			ret = clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts_total);
+			if (ret != 0)
+				return ret;
+		} else {
+			struct timespec ts_current;
+
+			ret = clock_gettime(CLOCK_MONOTONIC, &ts_current);
+			if (ret != 0)
+				return ret;
+
+			ts_total = timespec_sub(&ts_current, &ts_start);
+		}
+
+		ts_remaining = timespec_sub(&ts_run, &ts_total);
+	}
+
+	return 0;
+}
+
+/*
+ * Creates a cpu cgroup, burns a CPU for a few quanta, and verifies that
+ * cpu.stat shows the expected output.
+ */
+static int test_cpucg_stats(const char *root)
+{
+	int ret = KSFT_FAIL;
+	long usage_usec, user_usec, system_usec;
+	long usage_seconds = 2;
+	long expected_usage_usec = usage_seconds * USEC_PER_SEC;
+	char *cpucg;
+
+	cpucg = cg_name(root, "cpucg_test");
+	if (!cpucg)
+		goto cleanup;
+
+	if (cg_create(cpucg))
+		goto cleanup;
+
+	usage_usec = cg_read_key_long(cpucg, "cpu.stat", "usage_usec");
+	user_usec = cg_read_key_long(cpucg, "cpu.stat", "user_usec");
+	system_usec = cg_read_key_long(cpucg, "cpu.stat", "system_usec");
+	if (usage_usec != 0 || user_usec != 0 || system_usec != 0)
+		goto cleanup;
+
+	struct cpu_hog_func_param param = {
+		.nprocs = 1,
+		.ts = {
+			.tv_sec = usage_seconds,
+			.tv_nsec = 0,
+		},
+		.clock_type = CPU_HOG_CLOCK_PROCESS,
+	};
+	if (cg_run(cpucg, hog_cpus_timed, (void *)&param))
+		goto cleanup;
+
+	usage_usec = cg_read_key_long(cpucg, "cpu.stat", "usage_usec");
+	user_usec = cg_read_key_long(cpucg, "cpu.stat", "user_usec");
+	if (user_usec <= 0)
+		goto cleanup;
+
+	if (!values_close(usage_usec, expected_usage_usec, 1))
+		goto cleanup;
+
+	ret = KSFT_PASS;
+
+cleanup:
+	cg_destroy(cpucg);
+	free(cpucg);
+
+	return ret;
+}
+
+static int
+run_cpucg_weight_test(
+		const char *root,
+		pid_t (*spawn_child)(const struct cpu_hogger *child),
+		int (*validate)(const struct cpu_hogger *children, int num_children))
+{
+	int ret = KSFT_FAIL, i;
+	char *parent = NULL;
+	struct cpu_hogger children[3] = {NULL};
+
+	parent = cg_name(root, "cpucg_test_0");
+	if (!parent)
+		goto cleanup;
+
+	if (cg_create(parent))
+		goto cleanup;
+
+	if (cg_write(parent, "cgroup.subtree_control", "+cpu"))
+		goto cleanup;
+
+	for (i = 0; i < ARRAY_SIZE(children); i++) {
+		children[i].cgroup = cg_name_indexed(parent, "cpucg_child", i);
+		if (!children[i].cgroup)
+			goto cleanup;
+
+		if (cg_create(children[i].cgroup))
+			goto cleanup;
+
+		if (cg_write_numeric(children[i].cgroup, "cpu.weight",
+					50 * (i + 1)))
+			goto cleanup;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(children); i++) {
+		pid_t pid = spawn_child(&children[i]);
+		if (pid <= 0)
+			goto cleanup;
+		children[i].pid = pid;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(children); i++) {
+		int retcode;
+
+		waitpid(children[i].pid, &retcode, 0);
+		if (!WIFEXITED(retcode))
+			goto cleanup;
+		if (WEXITSTATUS(retcode))
+			goto cleanup;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(children); i++)
+		children[i].usage = cg_read_key_long(children[i].cgroup,
+				"cpu.stat", "usage_usec");
+
+	if (validate(children, ARRAY_SIZE(children)))
+		goto cleanup;
+
+	ret = KSFT_PASS;
+cleanup:
+	for (i = 0; i < ARRAY_SIZE(children); i++) {
+		cg_destroy(children[i].cgroup);
+		free(children[i].cgroup);
+	}
+	cg_destroy(parent);
+	free(parent);
+
+	return ret;
+}
+
+static pid_t weight_hog_ncpus(const struct cpu_hogger *child, int ncpus)
+{
+	long usage_seconds = 10;
+	struct cpu_hog_func_param param = {
+		.nprocs = ncpus,
+		.ts = {
+			.tv_sec = usage_seconds,
+			.tv_nsec = 0,
+		},
+		.clock_type = CPU_HOG_CLOCK_WALL,
+	};
+	return cg_run_nowait(child->cgroup, hog_cpus_timed, (void *)&param);
+}
+
+static pid_t weight_hog_all_cpus(const struct cpu_hogger *child)
+{
+	return weight_hog_ncpus(child, get_nprocs());
+}
+
+static int
+overprovision_validate(const struct cpu_hogger *children, int num_children)
+{
+	int ret = KSFT_FAIL, i;
+
+	for (i = 0; i < num_children - 1; i++) {
+		long delta;
+
+		if (children[i + 1].usage <= children[i].usage)
+			goto cleanup;
+
+		delta = children[i + 1].usage - children[i].usage;
+		if (!values_close(delta, children[0].usage, 35))
+			goto cleanup;
+	}
+
+	ret = KSFT_PASS;
+cleanup:
+	return ret;
+}
+
+/*
+ * First, this test creates the following hierarchy:
+ * A
+ * A/B     cpu.weight = 50
+ * A/C     cpu.weight = 100
+ * A/D     cpu.weight = 150
+ *
+ * A separate process is then created for each child cgroup which spawns as
+ * many threads as there are cores, and hogs each CPU as much as possible
+ * for some time interval.
+ *
+ * Once all of the children have exited, we verify that each child cgroup
+ * was given proportional runtime as informed by their cpu.weight.
+ */
+static int test_cpucg_weight_overprovisioned(const char *root)
+{
+	return run_cpucg_weight_test(root, weight_hog_all_cpus,
+			overprovision_validate);
+}
+
+static pid_t weight_hog_one_cpu(const struct cpu_hogger *child)
+{
+	return weight_hog_ncpus(child, 1);
+}
+
+static int
+underprovision_validate(const struct cpu_hogger *children, int num_children)
+{
+	int ret = KSFT_FAIL, i;
+
+	for (i = 0; i < num_children - 1; i++) {
+		if (!values_close(children[i + 1].usage, children[0].usage, 15))
+			goto cleanup;
+	}
+
+	ret = KSFT_PASS;
+cleanup:
+	return ret;
+}
+
+/*
+ * First, this test creates the following hierarchy:
+ * A
+ * A/B     cpu.weight = 50
+ * A/C     cpu.weight = 100
+ * A/D     cpu.weight = 150
+ *
+ * A separate process is then created for each child cgroup which spawns a
+ * single thread that hogs a CPU. The testcase is only run on systems that
+ * have at least one core per-thread in the child processes.
+ *
+ * Once all of the children have exited, we verify that each child cgroup
+ * had roughly the same runtime despite having different cpu.weight.
+ */
+static int test_cpucg_weight_underprovisioned(const char *root)
+{
+	// Only run the test if there are enough cores to avoid overprovisioning
+	// the system.
+	if (get_nprocs() < 4)
+		return KSFT_SKIP;
+
+	return run_cpucg_weight_test(root, weight_hog_one_cpu,
+			underprovision_validate);
+}
+
+static int
+run_cpucg_nested_weight_test(const char *root, bool overprovisioned)
+{
+	int ret = KSFT_FAIL, i;
+	char *parent = NULL, *child = NULL;
+	struct cpu_hogger leaf[3] = {NULL};
+	long nested_leaf_usage, child_usage;
+	int nprocs = get_nprocs();
+
+	if (!overprovisioned) {
+		if (nprocs < 4)
+			/*
+			 * Only run the test if there are enough cores to avoid overprovisioning
+			 * the system.
+			 */
+			return KSFT_SKIP;
+		nprocs /= 4;
+	}
+
+	parent = cg_name(root, "cpucg_test");
+	child = cg_name(parent, "cpucg_child");
+	if (!parent || !child)
+		goto cleanup;
+
+	if (cg_create(parent))
+		goto cleanup;
+	if (cg_write(parent, "cgroup.subtree_control", "+cpu"))
+		goto cleanup;
+
+	if (cg_create(child))
+		goto cleanup;
+	if (cg_write(child, "cgroup.subtree_control", "+cpu"))
+		goto cleanup;
+	if (cg_write(child, "cpu.weight", "1000"))
+		goto cleanup;
+
+	for (i = 0; i < ARRAY_SIZE(leaf); i++) {
+		const char *ancestor;
+		long weight;
+
+		if (i == 0) {
+			ancestor = parent;
+			weight = 1000;
+		} else {
+			ancestor = child;
+			weight = 5000;
+		}
+		leaf[i].cgroup = cg_name_indexed(ancestor, "cpucg_leaf", i);
+		if (!leaf[i].cgroup)
+			goto cleanup;
+
+		if (cg_create(leaf[i].cgroup))
+			goto cleanup;
+
+		if (cg_write_numeric(leaf[i].cgroup, "cpu.weight", weight))
+			goto cleanup;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(leaf); i++) {
+		pid_t pid;
+		struct cpu_hog_func_param param = {
+			.nprocs = nprocs,
+			.ts = {
+				.tv_sec = 10,
+				.tv_nsec = 0,
+			},
+			.clock_type = CPU_HOG_CLOCK_WALL,
+		};
+
+		pid = cg_run_nowait(leaf[i].cgroup, hog_cpus_timed,
+				(void *)&param);
+		if (pid <= 0)
+			goto cleanup;
+		leaf[i].pid = pid;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(leaf); i++) {
+		int retcode;
+
+		waitpid(leaf[i].pid, &retcode, 0);
+		if (!WIFEXITED(retcode))
+			goto cleanup;
+		if (WEXITSTATUS(retcode))
+			goto cleanup;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(leaf); i++) {
+		leaf[i].usage = cg_read_key_long(leaf[i].cgroup,
+				"cpu.stat", "usage_usec");
+		if (leaf[i].usage <= 0)
+			goto cleanup;
+	}
+
+	nested_leaf_usage = leaf[1].usage + leaf[2].usage;
+	if (overprovisioned) {
+		if (!values_close(leaf[0].usage, nested_leaf_usage, 15))
+			goto cleanup;
+	} else if (!values_close(leaf[0].usage * 2, nested_leaf_usage, 15))
+		goto cleanup;
+
+
+	child_usage = cg_read_key_long(child, "cpu.stat", "usage_usec");
+	if (child_usage <= 0)
+		goto cleanup;
+	if (!values_close(child_usage, nested_leaf_usage, 1))
+		goto cleanup;
+
+	ret = KSFT_PASS;
+cleanup:
+	for (i = 0; i < ARRAY_SIZE(leaf); i++) {
+		cg_destroy(leaf[i].cgroup);
+		free(leaf[i].cgroup);
+	}
+	cg_destroy(child);
+	free(child);
+	cg_destroy(parent);
+	free(parent);
+
+	return ret;
+}
+
+/*
+ * First, this test creates the following hierarchy:
+ * A
+ * A/B     cpu.weight = 1000
+ * A/C     cpu.weight = 1000
+ * A/C/D   cpu.weight = 5000
+ * A/C/E   cpu.weight = 5000
+ *
+ * A separate process is then created for each leaf, which spawn nproc threads
+ * that burn a CPU for a few seconds.
+ *
+ * Once all of those processes have exited, we verify that each of the leaf
+ * cgroups have roughly the same usage from cpu.stat.
+ */
+static int
+test_cpucg_nested_weight_overprovisioned(const char *root)
+{
+	return run_cpucg_nested_weight_test(root, true);
+}
+
+/*
+ * First, this test creates the following hierarchy:
+ * A
+ * A/B     cpu.weight = 1000
+ * A/C     cpu.weight = 1000
+ * A/C/D   cpu.weight = 5000
+ * A/C/E   cpu.weight = 5000
+ *
+ * A separate process is then created for each leaf, which nproc / 4 threads
+ * that burns a CPU for a few seconds.
+ *
+ * Once all of those processes have exited, we verify that each of the leaf
+ * cgroups have roughly the same usage from cpu.stat.
+ */
+static int
+test_cpucg_nested_weight_underprovisioned(const char *root)
+{
+	return run_cpucg_nested_weight_test(root, false);
+}
+
+/*
+ * This test creates a cgroup with some maximum value within a period, and
+ * verifies that a process in the cgroup is not overscheduled.
+ */
+static int test_cpucg_max(const char *root)
+{
+	int ret = KSFT_FAIL;
+	long usage_usec, user_usec;
+	long usage_seconds = 1;
+	long expected_usage_usec = usage_seconds * USEC_PER_SEC;
+	char *cpucg;
+
+	cpucg = cg_name(root, "cpucg_test");
+	if (!cpucg)
+		goto cleanup;
+
+	if (cg_create(cpucg))
+		goto cleanup;
+
+	if (cg_write(cpucg, "cpu.max", "1000"))
+		goto cleanup;
+
+	struct cpu_hog_func_param param = {
+		.nprocs = 1,
+		.ts = {
+			.tv_sec = usage_seconds,
+			.tv_nsec = 0,
+		},
+		.clock_type = CPU_HOG_CLOCK_WALL,
+	};
+	if (cg_run(cpucg, hog_cpus_timed, (void *)&param))
+		goto cleanup;
+
+	usage_usec = cg_read_key_long(cpucg, "cpu.stat", "usage_usec");
+	user_usec = cg_read_key_long(cpucg, "cpu.stat", "user_usec");
+	if (user_usec <= 0)
+		goto cleanup;
+
+	if (user_usec >= expected_usage_usec)
+		goto cleanup;
+
+	if (values_close(usage_usec, expected_usage_usec, 95))
+		goto cleanup;
+
+	ret = KSFT_PASS;
+
+cleanup:
+	cg_destroy(cpucg);
+	free(cpucg);
+
+	return ret;
+}
+
+/*
+ * This test verifies that a process inside of a nested cgroup whose parent
+ * group has a cpu.max value set, is properly throttled.
+ */
+static int test_cpucg_max_nested(const char *root)
+{
+	int ret = KSFT_FAIL;
+	long usage_usec, user_usec;
+	long usage_seconds = 1;
+	long expected_usage_usec = usage_seconds * USEC_PER_SEC;
+	char *parent, *child;
+
+	parent = cg_name(root, "cpucg_parent");
+	child = cg_name(parent, "cpucg_child");
+	if (!parent || !child)
+		goto cleanup;
+
+	if (cg_create(parent))
+		goto cleanup;
+
+	if (cg_write(parent, "cgroup.subtree_control", "+cpu"))
+		goto cleanup;
+
+	if (cg_create(child))
+		goto cleanup;
+
+	if (cg_write(parent, "cpu.max", "1000"))
+		goto cleanup;
+
+	struct cpu_hog_func_param param = {
+		.nprocs = 1,
+		.ts = {
+			.tv_sec = usage_seconds,
+			.tv_nsec = 0,
+		},
+		.clock_type = CPU_HOG_CLOCK_WALL,
+	};
+	if (cg_run(child, hog_cpus_timed, (void *)&param))
+		goto cleanup;
+
+	usage_usec = cg_read_key_long(child, "cpu.stat", "usage_usec");
+	user_usec = cg_read_key_long(child, "cpu.stat", "user_usec");
+	if (user_usec <= 0)
+		goto cleanup;
+
+	if (user_usec >= expected_usage_usec)
+		goto cleanup;
+
+	if (values_close(usage_usec, expected_usage_usec, 95))
+		goto cleanup;
+
+	ret = KSFT_PASS;
+
+cleanup:
+	cg_destroy(child);
+	free(child);
+	cg_destroy(parent);
+	free(parent);
+
+	return ret;
+}
+
+#define T(x) { x, #x }
+struct cpucg_test {
+	int (*fn)(const char *root);
+	const char *name;
+} tests[] = {
+	T(test_cpucg_subtree_control),
+	T(test_cpucg_stats),
+	T(test_cpucg_weight_overprovisioned),
+	T(test_cpucg_weight_underprovisioned),
+	T(test_cpucg_nested_weight_overprovisioned),
+	T(test_cpucg_nested_weight_underprovisioned),
+	T(test_cpucg_max),
+	T(test_cpucg_max_nested),
+};
+#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");
+
+	if (cg_read_strstr(root, "cgroup.subtree_control", "cpu"))
+		if (cg_write(root, "cgroup.subtree_control", "+cpu"))
+			ksft_exit_skip("Failed to set cpu controller\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;
+}

tools/testing/selftests/cgroup/test_stress.sh

 #!/bin/bash
 # SPDX-License-Identifier: GPL-2.0
 
-./with_stress.sh -s subsys -s fork ./test_core
+./with_stress.sh -s subsys -s fork ${OUTPUT:-.}/test_core