ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 249 insertions, 0 deletions

diff --git a/drivers/base/power/runtime-test.c b/drivers/base/power/runtime-test.c
new file mode 100644
index 000000000..1535ad2b0
--- /dev/null
+++ b/drivers/base/power/runtime-test.c
@@ -0,0 +1,249 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2025 Google, Inc.
+ */
+
+#include <linux/cleanup.h>
+#include <linux/pm_runtime.h>
+#include <kunit/device.h>
+#include <kunit/test.h>
+
+#define DEVICE_NAME "pm_runtime_test_device"
+
+static void pm_runtime_depth_test(struct kunit *test)
+{
+	struct device *dev = kunit_device_register(test, DEVICE_NAME);
+
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dev);
+
+	pm_runtime_enable(dev);
+
+	KUNIT_EXPECT_TRUE(test, pm_runtime_suspended(dev));
+	KUNIT_EXPECT_EQ(test, 0, pm_runtime_get_sync(dev));
+	KUNIT_EXPECT_TRUE(test, pm_runtime_active(dev));
+	KUNIT_EXPECT_EQ(test, 1, pm_runtime_get_sync(dev)); /* "already active" */
+	KUNIT_EXPECT_EQ(test, 0, pm_runtime_put_sync(dev));
+	KUNIT_EXPECT_EQ(test, 0, pm_runtime_put_sync(dev));
+	KUNIT_EXPECT_TRUE(test, pm_runtime_suspended(dev));
+}
+
+/* Test pm_runtime_put() and friends when already suspended. */
+static void pm_runtime_already_suspended_test(struct kunit *test)
+{
+	struct device *dev = kunit_device_register(test, DEVICE_NAME);
+
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dev);
+
+	pm_runtime_enable(dev);
+	KUNIT_EXPECT_TRUE(test, pm_runtime_suspended(dev));
+
+	pm_runtime_get_noresume(dev);
+	KUNIT_EXPECT_EQ(test, 1, pm_runtime_put_sync(dev));
+
+	KUNIT_EXPECT_EQ(test, 1, pm_runtime_suspend(dev));
+	KUNIT_EXPECT_EQ(test, 1, pm_runtime_autosuspend(dev));
+	KUNIT_EXPECT_EQ(test, 1, pm_request_autosuspend(dev));
+
+	pm_runtime_get_noresume(dev);
+	KUNIT_EXPECT_EQ(test, 1, pm_runtime_put_sync_autosuspend(dev));
+
+	pm_runtime_get_noresume(dev);
+	pm_runtime_put_autosuspend(dev);
+
+	/* Grab 2 refcounts */
+	pm_runtime_get_noresume(dev);
+	pm_runtime_get_noresume(dev);
+	/* The first put() sees usage_count 1 */
+	KUNIT_EXPECT_EQ(test, 0, pm_runtime_put_sync_autosuspend(dev));
+	/* The second put() sees usage_count 0 but tells us "already suspended". */
+	KUNIT_EXPECT_EQ(test, 1, pm_runtime_put_sync_autosuspend(dev));
+
+	/* Should have remained suspended the whole time. */
+	KUNIT_EXPECT_TRUE(test, pm_runtime_suspended(dev));
+}
+
+static void pm_runtime_idle_test(struct kunit *test)
+{
+	struct device *dev = kunit_device_register(test, DEVICE_NAME);
+
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dev);
+
+	pm_runtime_enable(dev);
+
+	KUNIT_EXPECT_TRUE(test, pm_runtime_suspended(dev));
+	KUNIT_EXPECT_EQ(test, 0, pm_runtime_get_sync(dev));
+	KUNIT_EXPECT_TRUE(test, pm_runtime_active(dev));
+	KUNIT_EXPECT_EQ(test, -EAGAIN, pm_runtime_idle(dev));
+	KUNIT_EXPECT_TRUE(test, pm_runtime_active(dev));
+	pm_runtime_put_noidle(dev);
+	KUNIT_EXPECT_TRUE(test, pm_runtime_active(dev));
+	KUNIT_EXPECT_EQ(test, 0, pm_runtime_idle(dev));
+	KUNIT_EXPECT_TRUE(test, pm_runtime_suspended(dev));
+	KUNIT_EXPECT_EQ(test, -EAGAIN, pm_runtime_idle(dev));
+	KUNIT_EXPECT_EQ(test, -EAGAIN, pm_request_idle(dev));
+}
+
+static void pm_runtime_disabled_test(struct kunit *test)
+{
+	struct device *dev = kunit_device_register(test, DEVICE_NAME);
+
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dev);
+
+	/* Never called pm_runtime_enable() */
+	KUNIT_EXPECT_FALSE(test, pm_runtime_enabled(dev));
+
+	/* "disabled" is treated as "active" */
+	KUNIT_EXPECT_TRUE(test, pm_runtime_active(dev));
+	KUNIT_EXPECT_FALSE(test, pm_runtime_suspended(dev));
+
+	/*
+	 * Note: these "fail", but they still acquire/release refcounts, so
+	 * keep them balanced.
+	 */
+	KUNIT_EXPECT_EQ(test, -EACCES, pm_runtime_get(dev));
+	pm_runtime_put(dev);
+
+	KUNIT_EXPECT_EQ(test, -EACCES, pm_runtime_get_sync(dev));
+	KUNIT_EXPECT_EQ(test, -EACCES, pm_runtime_put_sync(dev));
+
+	KUNIT_EXPECT_EQ(test, -EACCES, pm_runtime_get(dev));
+	pm_runtime_put_autosuspend(dev);
+
+	KUNIT_EXPECT_EQ(test, -EACCES, pm_runtime_resume_and_get(dev));
+	KUNIT_EXPECT_EQ(test, -EACCES, pm_runtime_idle(dev));
+	KUNIT_EXPECT_EQ(test, -EACCES, pm_request_idle(dev));
+	KUNIT_EXPECT_EQ(test, -EACCES, pm_request_resume(dev));
+	KUNIT_EXPECT_EQ(test, -EACCES, pm_request_autosuspend(dev));
+	KUNIT_EXPECT_EQ(test, -EACCES, pm_runtime_suspend(dev));
+	KUNIT_EXPECT_EQ(test, -EACCES, pm_runtime_resume(dev));
+	KUNIT_EXPECT_EQ(test, -EACCES, pm_runtime_autosuspend(dev));
+
+	/* Still disabled */
+	KUNIT_EXPECT_TRUE(test, pm_runtime_active(dev));
+	KUNIT_EXPECT_FALSE(test, pm_runtime_enabled(dev));
+}
+
+static void pm_runtime_error_test(struct kunit *test)
+{
+	struct device *dev = kunit_device_register(test, DEVICE_NAME);
+
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dev);
+
+	pm_runtime_enable(dev);
+	KUNIT_EXPECT_TRUE(test, pm_runtime_suspended(dev));
+
+	/* Fake a .runtime_resume() error */
+	dev->power.runtime_error = -EIO;
+
+	/*
+	 * Note: these "fail", but they still acquire/release refcounts, so
+	 * keep them balanced.
+	 */
+	KUNIT_EXPECT_EQ(test, -EINVAL, pm_runtime_get(dev));
+	pm_runtime_put(dev);
+
+	KUNIT_EXPECT_EQ(test, -EINVAL, pm_runtime_get_sync(dev));
+	KUNIT_EXPECT_EQ(test, -EINVAL, pm_runtime_put_sync(dev));
+
+	KUNIT_EXPECT_EQ(test, -EINVAL, pm_runtime_get(dev));
+	pm_runtime_put_autosuspend(dev);
+
+	KUNIT_EXPECT_EQ(test, -EINVAL, pm_runtime_get(dev));
+	KUNIT_EXPECT_EQ(test, -EINVAL, pm_runtime_put_sync_autosuspend(dev));
+
+	KUNIT_EXPECT_EQ(test, -EINVAL, pm_runtime_resume_and_get(dev));
+	KUNIT_EXPECT_EQ(test, -EINVAL, pm_runtime_idle(dev));
+	KUNIT_EXPECT_EQ(test, -EINVAL, pm_request_idle(dev));
+	KUNIT_EXPECT_EQ(test, -EINVAL, pm_request_resume(dev));
+	KUNIT_EXPECT_EQ(test, -EINVAL, pm_request_autosuspend(dev));
+	KUNIT_EXPECT_EQ(test, -EINVAL, pm_runtime_suspend(dev));
+	KUNIT_EXPECT_EQ(test, -EINVAL, pm_runtime_resume(dev));
+	KUNIT_EXPECT_EQ(test, -EINVAL, pm_runtime_autosuspend(dev));
+
+	/* Error is still pending */
+	KUNIT_EXPECT_TRUE(test, pm_runtime_suspended(dev));
+	KUNIT_EXPECT_EQ(test, -EIO, dev->power.runtime_error);
+	/* Clear error */
+	KUNIT_EXPECT_EQ(test, 0, pm_runtime_set_suspended(dev));
+	KUNIT_EXPECT_EQ(test, 0, dev->power.runtime_error);
+	/* Still suspended */
+	KUNIT_EXPECT_TRUE(test, pm_runtime_suspended(dev));
+
+	KUNIT_EXPECT_EQ(test, 0, pm_runtime_get(dev));
+	pm_runtime_barrier(dev);
+	pm_runtime_put(dev);
+	pm_runtime_suspend(dev); /* flush the put(), to suspend */
+	KUNIT_EXPECT_TRUE(test, pm_runtime_suspended(dev));
+
+	KUNIT_EXPECT_EQ(test, 0, pm_runtime_get_sync(dev));
+	KUNIT_EXPECT_EQ(test, 0, pm_runtime_put_sync(dev));
+
+	KUNIT_EXPECT_EQ(test, 0, pm_runtime_get_sync(dev));
+	pm_runtime_put_autosuspend(dev);
+
+	KUNIT_EXPECT_EQ(test, 0, pm_runtime_resume_and_get(dev));
+
+	/*
+	 * The following should all return -EAGAIN (usage is non-zero) or 1
+	 * (already resumed).
+	 */
+	KUNIT_EXPECT_EQ(test, -EAGAIN, pm_runtime_idle(dev));
+	KUNIT_EXPECT_EQ(test, -EAGAIN, pm_request_idle(dev));
+	KUNIT_EXPECT_EQ(test, 1, pm_request_resume(dev));
+	KUNIT_EXPECT_EQ(test, -EAGAIN, pm_request_autosuspend(dev));
+	KUNIT_EXPECT_EQ(test, -EAGAIN, pm_runtime_suspend(dev));
+	KUNIT_EXPECT_EQ(test, 1, pm_runtime_resume(dev));
+	KUNIT_EXPECT_EQ(test, -EAGAIN, pm_runtime_autosuspend(dev));
+
+	KUNIT_EXPECT_EQ(test, 0, pm_runtime_put_sync(dev));
+
+	/* Suspended again */
+	KUNIT_EXPECT_TRUE(test, pm_runtime_suspended(dev));
+}
+
+/*
+ * Explore a typical probe() sequence in which a device marks itself powered,
+ * but doesn't hold any runtime PM reference, so it suspends as soon as it goes
+ * idle.
+ */
+static void pm_runtime_probe_active_test(struct kunit *test)
+{
+	struct device *dev = kunit_device_register(test, DEVICE_NAME);
+
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dev);
+
+	KUNIT_EXPECT_TRUE(test, pm_runtime_status_suspended(dev));
+
+	KUNIT_EXPECT_EQ(test, 0, pm_runtime_set_active(dev));
+	KUNIT_EXPECT_TRUE(test, pm_runtime_active(dev));
+
+	pm_runtime_enable(dev);
+	KUNIT_EXPECT_TRUE(test, pm_runtime_active(dev));
+
+	/* Nothing to flush. We stay active. */
+	pm_runtime_barrier(dev);
+	KUNIT_EXPECT_TRUE(test, pm_runtime_active(dev));
+
+	/* Ask for idle? Now we suspend. */
+	KUNIT_EXPECT_EQ(test, 0, pm_runtime_idle(dev));
+	KUNIT_EXPECT_TRUE(test, pm_runtime_suspended(dev));
+}
+
+static struct kunit_case pm_runtime_test_cases[] = {
+	KUNIT_CASE(pm_runtime_depth_test),
+	KUNIT_CASE(pm_runtime_already_suspended_test),
+	KUNIT_CASE(pm_runtime_idle_test),
+	KUNIT_CASE(pm_runtime_disabled_test),
+	KUNIT_CASE(pm_runtime_error_test),
+	KUNIT_CASE(pm_runtime_probe_active_test),
+	{}
+};
+
+static struct kunit_suite pm_runtime_test_suite = {
+	.name = "pm_runtime_test_cases",
+	.test_cases = pm_runtime_test_cases,
+};
+
+kunit_test_suite(pm_runtime_test_suite);
+MODULE_DESCRIPTION("Runtime power management unit test suite");
+MODULE_LICENSE("GPL");