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Message-ID: <20250805032940.3587891-6-ynaffit@google.com>
Date: Mon, 4 Aug 2025 20:29:42 -0700
From: Tiffany Yang <ynaffit@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: John Stultz <jstultz@...gle.com>, Thomas Gleixner <tglx@...utronix.de>,
Stephen Boyd <sboyd@...nel.org>, Anna-Maria Behnsen <anna-maria@...utronix.de>,
Frederic Weisbecker <frederic@...nel.org>, Tejun Heo <tj@...nel.org>,
Johannes Weiner <hannes@...xchg.org>, "Michal Koutný" <mkoutny@...e.com>,
"Rafael J. Wysocki" <rafael@...nel.org>, Pavel Machek <pavel@...nel.org>,
Roman Gushchin <roman.gushchin@...ux.dev>, Chen Ridong <chenridong@...wei.com>,
kernel-team@...roid.com, Jonathan Corbet <corbet@....net>, Shuah Khan <shuah@...nel.org>,
cgroups@...r.kernel.org, linux-doc@...r.kernel.org,
linux-kselftest@...r.kernel.org
Subject: [RFC PATCH v3 2/2] cgroup: selftests: Add tests for freezer time
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@...gle.com>
---
tools/testing/selftests/cgroup/test_freezer.c | 686 ++++++++++++++++++
1 file changed, 686 insertions(+)
diff --git a/tools/testing/selftests/cgroup/test_freezer.c b/tools/testing/selftests/cgroup/test_freezer.c
index 8730645d363a..c0880ecfa814 100644
--- a/tools/testing/selftests/cgroup/test_freezer.c
+++ b/tools/testing/selftests/cgroup/test_freezer.c
@@ -804,6 +804,685 @@ static int test_cgfreezer_vfork(const char *root)
return ret;
}
+/*
+ * Get the current freeze_time_total for the cgroup.
+ */
+static long cg_check_freezetime(const char *cgroup)
+{
+ return cg_read_key_long(cgroup, "cgroup.freeze.stat.local",
+ "freeze_time_total ");
+}
+
+/*
+ * 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;
+ int i;
+
+ 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) {
+ if (curr < 0)
+ ret = KSFT_SKIP;
+ else
+ debug("Expect time (%ld) to be 0\n", curr);
+
+ goto cleanup;
+ }
+
+ /*
+ * 2) Freeze the cgroup. Check that its freeze time is
+ * larger than 0.
+ */
+ if (cg_freeze_nowait(cgroup, true))
+ goto cleanup;
+ prev = curr;
+ curr = cg_check_freezetime(cgroup);
+ if (curr <= prev) {
+ debug("Expect time (%ld) > 0\n", curr);
+ goto cleanup;
+ }
+
+ /*
+ * 3) Sleep for 100 us. Check that the freeze time is at
+ * least 100 us larger than it was at 2).
+ */
+ usleep(100);
+ prev = curr;
+ curr = cg_check_freezetime(cgroup);
+ if ((curr - prev) < 100) {
+ debug("Expect time (%ld) to be at least 100 us more than previous check (%ld)\n",
+ curr, prev);
+ 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) 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;
+ int i;
+
+ 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) {
+ if (curr < 0)
+ ret = KSFT_SKIP;
+ else
+ 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;
+ }
+
+ /*
+ * 3) Freeze the cgroup. Check that its freeze time is
+ * larger than 0.
+ */
+ if (cg_freeze_nowait(cgroup, true))
+ goto cleanup;
+ prev = curr;
+ curr = cg_check_freezetime(cgroup);
+ if (curr <= prev) {
+ debug("Expect time (%ld) > 0\n", curr);
+ goto cleanup;
+ }
+
+ /*
+ * 4) Sleep for 100 us. Check that the freeze time is at
+ * least 100 us larger than it was at 3).
+ */
+ usleep(100);
+ prev = curr;
+ curr = cg_check_freezetime(cgroup);
+ if ((curr - prev) < 100) {
+ debug("Expect time (%ld) to be at least 100 us 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) Sleep for 100 us. Check that the freeze time is the
+ * same as at 5).
+ */
+ usleep(100);
+ 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) {
+ if (curr < 0)
+ ret = KSFT_SKIP;
+ else
+ 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, i;
+
+ 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 +1498,13 @@ 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
--
2.50.1.565.gc32cd1483b-goog
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