Re: [PATCH v4 2/2] cgroup: selftests: Add tests for freezer time

[Chen Ridong <chenridong@huaweicloud.com>]

On 2025/8/22 9:37, Tiffany Yang wrote:
> Test cgroup v2 freezer time stat. Freezer time accounting should
> be independent of other cgroups in the hierarchy and should increase
> iff a cgroup is CGRP_FREEZE (regardless of whether it reaches
> CGRP_FROZEN).
> 
> Skip these tests on systems without freeze time accounting.
> 
> Signed-off-by: Tiffany Yang <ynaffit@google.com>
> Cc: Michal Koutný <mkoutny@suse.com>
> ---
> v3 -> v4:
> * Clean up logic around skipping selftests and decrease granularity of
>   sleep times, as suggested by Michal.
> ---
>  tools/testing/selftests/cgroup/test_freezer.c | 663 ++++++++++++++++++
>  1 file changed, 663 insertions(+)
> 
> diff --git a/tools/testing/selftests/cgroup/test_freezer.c b/tools/testing/selftests/cgroup/test_freezer.c
> index 8730645d363a..dfb763819581 100644
> --- a/tools/testing/selftests/cgroup/test_freezer.c
> +++ b/tools/testing/selftests/cgroup/test_freezer.c
> @@ -804,6 +804,662 @@ static int test_cgfreezer_vfork(const char *root)
>  	return ret;
>  }
>  
> +/*
> + * Get the current frozen_usec for the cgroup.
> + */
> +static long cg_check_freezetime(const char *cgroup)
> +{
> +	return cg_read_key_long(cgroup, "cgroup.stat.local",
> +				"frozen_usec ");
> +}
> +
> +/*
> + * Test that the freeze time will behave as expected for an empty cgroup.
> + */
> +static int test_cgfreezer_time_empty(const char *root)
> +{
> +	int ret = KSFT_FAIL;
> +	char *cgroup = NULL;
> +	long prev, curr;
> +
> +	cgroup = cg_name(root, "cg_time_test_empty");
> +	if (!cgroup)
> +		goto cleanup;
> +
> +	/*
> +	 * 1) Create an empty cgroup and check that its freeze time
> +	 *    is 0.
> +	 */
> +	if (cg_create(cgroup))
> +		goto cleanup;
> +
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr < 0) {
> +		ret = KSFT_SKIP;
> +		goto cleanup;
> +	}
> +	if (curr > 0) {
> +		debug("Expect time (%ld) to be 0\n", curr);
> +		goto cleanup;
> +	}
> +

Perhaps we can simply use if (curr != 0) for the condition?

> +	if (cg_freeze_nowait(cgroup, true))
> +		goto cleanup;
> +
> +	/*
> +	 * 2) Sleep for 1000 us. Check that the freeze time is at
> +	 *    least 1000 us.
> +	 */
> +	usleep(1000);
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr < 1000) {
> +		debug("Expect time (%ld) to be at least 1000 us\n",
> +		      curr);
> +		goto cleanup;
> +	}
> +
> +	/*
> +	 * 3) Unfreeze the cgroup. Check that the freeze time is
> +	 *    larger than at 2).
> +	 */
> +	if (cg_freeze_nowait(cgroup, false))
> +		goto cleanup;
> +	prev = curr;
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr <= prev) {
> +		debug("Expect time (%ld) to be more than previous check (%ld)\n",
> +		      curr, prev);
> +		goto cleanup;
> +	}
> +
> +	/*
> +	 * 4) Check the freeze time again to ensure that it has not
> +	 *    changed.
> +	 */
> +	prev = curr;
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr != prev) {
> +		debug("Expect time (%ld) to be unchanged from previous check (%ld)\n",
> +		      curr, prev);
> +		goto cleanup;
> +	}
> +
> +	ret = KSFT_PASS;
> +
> +cleanup:
> +	if (cgroup)
> +		cg_destroy(cgroup);
> +	free(cgroup);
> +	return ret;
> +}
> +
> +/*
> + * A simple test for cgroup freezer time accounting. This test follows
> + * the same flow as test_cgfreezer_time_empty, but with a single process
> + * in the cgroup.
> + */
> +static int test_cgfreezer_time_simple(const char *root)
> +{
> +	int ret = KSFT_FAIL;
> +	char *cgroup = NULL;
> +	long prev, curr;
> +
> +	cgroup = cg_name(root, "cg_time_test_simple");
> +	if (!cgroup)
> +		goto cleanup;
> +
> +	/*
> +	 * 1) Create a cgroup and check that its freeze time is 0.
> +	 */
> +	if (cg_create(cgroup))
> +		goto cleanup;
> +
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr < 0) {
> +		ret = KSFT_SKIP;
> +		goto cleanup;
> +	}
> +	if (curr > 0) {
> +		debug("Expect time (%ld) to be 0\n", curr);
> +		goto cleanup;
> +	}
> +
> +	/*
> +	 * 2) Populate the cgroup with one child and check that the
> +	 *    freeze time is still 0.
> +	 */
> +	cg_run_nowait(cgroup, child_fn, NULL);
> +	prev = curr;
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr > prev) {
> +		debug("Expect time (%ld) to be 0\n", curr);
> +		goto cleanup;
> +	}
> +
> +	if (cg_freeze_nowait(cgroup, true))
> +		goto cleanup;
> +
> +	/*
> +	 * 3) Sleep for 1000 us. Check that the freeze time is at
> +	 *    least 1000 us.
> +	 */
> +	usleep(1000);
> +	prev = curr;
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr < 1000) {
> +		debug("Expect time (%ld) to be at least 1000 us\n",
> +		      curr);
> +		goto cleanup;
> +	}
> +
> +	/*
> +	 * 4) Unfreeze the cgroup. Check that the freeze time is
> +	 *    larger than at 3).
> +	 */
> +	if (cg_freeze_nowait(cgroup, false))
> +		goto cleanup;
> +	prev = curr;
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr <= prev) {
> +		debug("Expect time (%ld) to be more than previous check (%ld)\n",
> +		      curr, prev);
> +		goto cleanup;
> +	}
> +
> +	/*
> +	 * 5) Sleep for 1000 us. Check that the freeze time is the
> +	 *    same as at 4).
> +	 */
> +	usleep(1000);
> +	prev = curr;
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr != prev) {
> +		debug("Expect time (%ld) to be unchanged from previous check (%ld)\n",
> +		      curr, prev);
> +		goto cleanup;
> +	}
> +
> +	ret = KSFT_PASS;
> +
> +cleanup:
> +	if (cgroup)
> +		cg_destroy(cgroup);
> +	free(cgroup);
> +	return ret;
> +}
> +
> +/*
> + * Test that freezer time accounting works as expected, even while we're
> + * populating a cgroup with processes.
> + */
> +static int test_cgfreezer_time_populate(const char *root)
> +{
> +	int ret = KSFT_FAIL;
> +	char *cgroup = NULL;
> +	long prev, curr;
> +	int i;
> +
> +	cgroup = cg_name(root, "cg_time_test_populate");
> +	if (!cgroup)
> +		goto cleanup;
> +
> +	if (cg_create(cgroup))
> +		goto cleanup;
> +
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr < 0) {
> +		ret = KSFT_SKIP;
> +		goto cleanup;
> +	}
> +	if (curr > 0) {
> +		debug("Expect time (%ld) to be 0\n", curr);
> +		goto cleanup;
> +	}
> +
> +	/*
> +	 * 1) Populate the cgroup with 100 processes. Check that
> +	 *    the freeze time is 0.
> +	 */
> +	for (i = 0; i < 100; i++)
> +		cg_run_nowait(cgroup, child_fn, NULL);
> +	prev = curr;
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr != prev) {
> +		debug("Expect time (%ld) to be 0\n", curr);
> +		goto cleanup;
> +	}
> +
> +	/*
> +	 * 2) Wait for the group to become fully populated. Check
> +	 *    that the freeze time is 0.
> +	 */
> +	if (cg_wait_for_proc_count(cgroup, 100))
> +		goto cleanup;
> +	prev = curr;
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr != prev) {
> +		debug("Expect time (%ld) to be 0\n", curr);
> +		goto cleanup;
> +	}
> +
> +	/*
> +	 * 3) Freeze the cgroup and then populate it with 100 more
> +	 *    processes. Check that the freeze time continues to grow.
> +	 */
> +	if (cg_freeze_nowait(cgroup, true))
> +		goto cleanup;
> +	prev = curr;
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr <= prev) {
> +		debug("Expect time (%ld) to be more than previous check (%ld)\n",
> +		      curr, prev);
> +		goto cleanup;
> +	}
> +
> +	for (i = 0; i < 100; i++)
> +		cg_run_nowait(cgroup, child_fn, NULL);
> +	prev = curr;
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr <= prev) {
> +		debug("Expect time (%ld) to be more than previous check (%ld)\n",
> +		      curr, prev);
> +		goto cleanup;
> +	}
> +
> +	/*
> +	 * 4) Wait for the group to become fully populated. Check
> +	 *    that the freeze time is larger than at 3).
> +	 */
> +	if (cg_wait_for_proc_count(cgroup, 200))
> +		goto cleanup;
> +	prev = curr;
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr <= prev) {
> +		debug("Expect time (%ld) to be more than previous check (%ld)\n",
> +		      curr, prev);
> +		goto cleanup;
> +	}
> +
> +	/*
> +	 * 5) Unfreeze the cgroup. Check that the freeze time is
> +	 *    larger than at 4).
> +	 */
> +	if (cg_freeze_nowait(cgroup, false))
> +		goto cleanup;
> +	prev = curr;
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr <= prev) {
> +		debug("Expect time (%ld) to be more than previous check (%ld)\n",
> +		      curr, prev);
> +		goto cleanup;
> +	}
> +
> +	/*
> +	 * 6) Kill the processes. Check that the freeze time is the
> +	 *    same as it was at 5).
> +	 */
> +	if (cg_killall(cgroup))
> +		goto cleanup;
> +	prev = curr;
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr != prev) {
> +		debug("Expect time (%ld) to be unchanged from previous check (%ld)\n",
> +		      curr, prev);
> +		goto cleanup;
> +	}
> +
> +	/*
> +	 * 7) Freeze and unfreeze the cgroup. Check that the freeze
> +	 *    time is larger than it was at 6).
> +	 */
> +	if (cg_freeze_nowait(cgroup, true))
> +		goto cleanup;
> +	if (cg_freeze_nowait(cgroup, false))
> +		goto cleanup;
> +	prev = curr;
> +	curr = cg_check_freezetime(cgroup);
> +	if (curr <= prev) {
> +		debug("Expect time (%ld) to be more than previous check (%ld)\n",
> +		      curr, prev);
> +		goto cleanup;
> +	}
> +
> +	ret = KSFT_PASS;
> +
> +cleanup:
> +	if (cgroup)
> +		cg_destroy(cgroup);
> +	free(cgroup);
> +	return ret;
> +}
> +
> +/*
> + * Test that frozen time for a cgroup continues to work as expected,
> + * even as processes are migrated. Frozen cgroup A's freeze time should
> + * continue to increase and running cgroup B's should stay 0.
> + */
> +static int test_cgfreezer_time_migrate(const char *root)
> +{
> +	long prev_A, curr_A, curr_B;
> +	char *cgroup[2] = {0};
> +	int ret = KSFT_FAIL;
> +	int pid;
> +
> +	cgroup[0] = cg_name(root, "cg_time_test_migrate_A");
> +	if (!cgroup[0])
> +		goto cleanup;
> +
> +	cgroup[1] = cg_name(root, "cg_time_test_migrate_B");
> +	if (!cgroup[1])
> +		goto cleanup;
> +
> +	if (cg_create(cgroup[0]))
> +		goto cleanup;
> +
> +	if (cg_check_freezetime(cgroup[0]) < 0) {
> +		ret = KSFT_SKIP;
> +		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;
> +
> +	curr_A = cg_check_freezetime(cgroup[0]);
> +	if (curr_A) {
> +		debug("Expect time (%ld) to be 0\n", curr_A);
> +		goto cleanup;
> +	}
> +	curr_B = cg_check_freezetime(cgroup[1]);
> +	if (curr_B) {
> +		debug("Expect time (%ld) to be 0\n", curr_B);
> +		goto cleanup;
> +	}
> +
> +	/*
> +	 * Freeze cgroup A.
> +	 */
> +	if (cg_freeze_wait(cgroup[0], true))
> +		goto cleanup;
> +	prev_A = curr_A;
> +	curr_A = cg_check_freezetime(cgroup[0]);
> +	if (curr_A <= prev_A) {
> +		debug("Expect time (%ld) to be > 0\n", curr_A);
> +		goto cleanup;
> +	}
> +
> +	/*
> +	 * Migrate from A (frozen) to B (running).
> +	 */
> +	if (cg_enter(cgroup[1], pid))
> +		goto cleanup;
> +
> +	usleep(1000);
> +	curr_B = cg_check_freezetime(cgroup[1]);
> +	if (curr_B) {
> +		debug("Expect time (%ld) to be 0\n", curr_B);
> +		goto cleanup;
> +	}
> +
> +	prev_A = curr_A;
> +	curr_A = cg_check_freezetime(cgroup[0]);
> +	if (curr_A <= prev_A) {
> +		debug("Expect time (%ld) to be more than previous check (%ld)\n",
> +		      curr_A, prev_A);
> +		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 creates a cgroup and freezes it. Then it creates a child cgroup.
> + * After that it checks that the child cgroup has a non-zero freeze time
> + * that is less than the parent's. Next, it freezes the child, unfreezes
> + * the parent, and sleeps. Finally, it checks that the child's freeze
> + * time has grown larger than the parent's.
> + */
> +static int test_cgfreezer_time_parent(const char *root)
> +{
> +	char *parent, *child = NULL;
> +	int ret = KSFT_FAIL;
> +	long ptime, ctime;
> +
> +	parent = cg_name(root, "cg_test_parent_A");
> +	if (!parent)
> +		goto cleanup;
> +
> +	child = cg_name(parent, "cg_test_parent_B");
> +	if (!child)
> +		goto cleanup;
> +
> +	if (cg_create(parent))
> +		goto cleanup;
> +
> +	if (cg_check_freezetime(parent) < 0) {
> +		ret = KSFT_SKIP;
> +		goto cleanup;
> +	}
> +
> +	if (cg_freeze_wait(parent, true))
> +		goto cleanup;
> +
> +	usleep(1000);
> +	if (cg_create(child))
> +		goto cleanup;
> +
> +	if (cg_check_frozen(child, true))
> +		goto cleanup;
> +
> +	/*
> +	 * Since the parent was frozen the entire time the child cgroup
> +	 * was being created, we expect the parent's freeze time to be
> +	 * larger than the child's.
> +	 *
> +	 * Ideally, we would be able to check both times simultaneously,
> +	 * but here we get the child's after we get the parent's.
> +	 */
> +	ptime = cg_check_freezetime(parent);
> +	ctime = cg_check_freezetime(child);
> +	if (ptime <= ctime) {
> +		debug("Expect ptime (%ld) > ctime (%ld)\n", ptime, ctime);
> +		goto cleanup;
> +	}
> +
> +	if (cg_freeze_nowait(child, true))
> +		goto cleanup;
> +
> +	if (cg_freeze_wait(parent, false))
> +		goto cleanup;
> +
> +	if (cg_check_frozen(child, true))
> +		goto cleanup;
> +
> +	usleep(100000);
> +
> +	ctime = cg_check_freezetime(child);
> +	ptime = cg_check_freezetime(parent);
> +
> +	if (ctime <= ptime) {
> +		debug("Expect ctime (%ld) > ptime (%ld)\n", ctime, ptime);
> +		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 a parent cgroup and a child cgroup. Then, it freezes
> + * the child and checks that the child's freeze time is greater than the
> + * parent's, which should be zero.
> + */
> +static int test_cgfreezer_time_child(const char *root)
> +{
> +	char *parent, *child = NULL;
> +	int ret = KSFT_FAIL;
> +	long ptime, ctime;
> +
> +	parent = cg_name(root, "cg_test_child_A");
> +	if (!parent)
> +		goto cleanup;
> +
> +	child = cg_name(parent, "cg_test_child_B");
> +	if (!child)
> +		goto cleanup;
> +
> +	if (cg_create(parent))
> +		goto cleanup;
> +
> +	if (cg_check_freezetime(parent) < 0) {
> +		ret = KSFT_SKIP;
> +		goto cleanup;
> +	}
> +
> +	if (cg_create(child))
> +		goto cleanup;
> +
> +	if (cg_freeze_wait(child, true))
> +		goto cleanup;
> +
> +	ctime = cg_check_freezetime(child);
> +	ptime = cg_check_freezetime(parent);
> +	if (ptime != 0) {
> +		debug("Expect ptime (%ld) to be 0\n", ptime);
> +		goto cleanup;
> +	}
> +
> +	if (ctime <= ptime) {
> +		debug("Expect ctime (%ld) <= ptime (%ld)\n", ctime, ptime);
> +		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 the following hierarchy:
> + *    A
> + *    |
> + *    B
> + *    |
> + *    C
> + *
> + * Then it freezes the cgroups in the order C, B, A.
> + * Then it unfreezes the cgroups in the order A, B, C.
> + * Then it checks that C's freeze time is larger than B's and
> + * that B's is larger than A's.
> + */
> +static int test_cgfreezer_time_nested(const char *root)
> +{
> +	char *cgroup[3] = {0};
> +	int ret = KSFT_FAIL;
> +	long time[3] = {0};
> +	int i;
> +
> +	cgroup[0] = cg_name(root, "cg_test_time_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;
> +
> +	if (cg_create(cgroup[0]))
> +		goto cleanup;
> +
> +	if (cg_check_freezetime(cgroup[0]) < 0) {
> +		ret = KSFT_SKIP;
> +		goto cleanup;
> +	}
> +
> +	if (cg_create(cgroup[1]))
> +		goto cleanup;
> +
> +	if (cg_create(cgroup[2]))
> +		goto cleanup;
> +
> +	if (cg_freeze_nowait(cgroup[2], true))
> +		goto cleanup;
> +
> +	if (cg_freeze_nowait(cgroup[1], true))
> +		goto cleanup;
> +
> +	if (cg_freeze_nowait(cgroup[0], true))
> +		goto cleanup;
> +
> +	usleep(1000);
> +
> +	if (cg_freeze_nowait(cgroup[0], false))
> +		goto cleanup;
> +
> +	if (cg_freeze_nowait(cgroup[1], false))
> +		goto cleanup;
> +
> +	if (cg_freeze_nowait(cgroup[2], false))
> +		goto cleanup;
> +
> +	time[2] = cg_check_freezetime(cgroup[2]);
> +	time[1] = cg_check_freezetime(cgroup[1]);
> +	time[0] = cg_check_freezetime(cgroup[0]);
> +
> +	if (time[2] <= time[1]) {
> +		debug("Expect C's time (%ld) > B's time (%ld)", time[2], time[1]);
> +		goto cleanup;
> +	}
> +
> +	if (time[1] <= time[0]) {
> +		debug("Expect B's time (%ld) > A's time (%ld)", time[1], time[0]);
> +		goto cleanup;
> +	}
> +
> +	ret = KSFT_PASS;
> +
> +cleanup:
> +	for (i = 2; i >= 0 && cgroup[i]; i--) {
> +		cg_destroy(cgroup[i]);
> +		free(cgroup[i]);
> +	}
> +
> +	return ret;
> +}
> +
>  #define T(x) { x, #x }
>  struct cgfreezer_test {
>  	int (*fn)(const char *root);
> @@ -819,6 +1475,13 @@ struct cgfreezer_test {
>  	T(test_cgfreezer_stopped),
>  	T(test_cgfreezer_ptraced),
>  	T(test_cgfreezer_vfork),
> +	T(test_cgfreezer_time_empty),
> +	T(test_cgfreezer_time_simple),
> +	T(test_cgfreezer_time_populate),
> +	T(test_cgfreezer_time_migrate),
> +	T(test_cgfreezer_time_parent),
> +	T(test_cgfreezer_time_child),
> +	T(test_cgfreezer_time_nested),
>  };
>  #undef T
>  

-- 
Best regards,
Ridong