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, 153 insertions, 0 deletions

diff --git a/drivers/clk/clk-divider_test.c b/drivers/clk/clk-divider_test.c
new file mode 100644
index 000000000..8ee161412
--- /dev/null
+++ b/drivers/clk/clk-divider_test.c
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit tests for clk_divider_bestdiv()
+ */
+#include <kunit/test.h>
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/limits.h>
+#include <linux/units.h>
+
+#define PARENT_RATE_1GHZ	GIGA
+#define PARENT_RATE_2GHZ	(2 * GIGA)
+#define PARENT_RATE_4GHZ	(4 * GIGA)
+
+KUNIT_DEFINE_ACTION_WRAPPER(clk_hw_unregister_fixed_rate_wrapper,
+			    clk_hw_unregister_fixed_rate, struct clk_hw *);
+KUNIT_DEFINE_ACTION_WRAPPER(clk_hw_unregister_divider_wrapper,
+			    clk_hw_unregister_divider, struct clk_hw *);
+KUNIT_DEFINE_ACTION_WRAPPER(clk_hw_unregister_mux_wrapper,
+			    clk_hw_unregister_mux, struct clk_hw *);
+
+static const struct clk_div_table bestdiv_table[] = {
+	{ .val = 0, .div = 2 },
+	{ .val = 1, .div = 4 },
+	{ .val = 2, .div = 8 },
+	{ /* sentinel */ }
+};
+
+/*
+ * Test that clk_round_rate(clk, ULONG_MAX) returns the maximum achievable
+ * rate for a divider clock.
+ */
+static void clk_divider_bestdiv_ulong_max_returns_max_rate(struct kunit *test)
+{
+	struct clk_hw *parent_hw, *div_hw;
+	unsigned long rate;
+	u32 *fake_reg;
+
+	fake_reg = kunit_kzalloc(test, sizeof(*fake_reg), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, fake_reg);
+
+	parent_hw = clk_hw_register_fixed_rate(NULL, "bestdiv-parent",
+					       NULL, 0, PARENT_RATE_1GHZ);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, parent_hw);
+	KUNIT_ASSERT_EQ(test, 0,
+			kunit_add_action_or_reset(test, clk_hw_unregister_fixed_rate_wrapper,
+						  parent_hw));
+
+	div_hw = clk_hw_register_divider_table(NULL, "bestdiv-div",
+					       "bestdiv-parent",
+					       CLK_SET_RATE_PARENT,
+					       (void __iomem __force *)fake_reg,
+					       0, 2, 0, bestdiv_table, NULL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, div_hw);
+	KUNIT_ASSERT_EQ(test, 0,
+			kunit_add_action_or_reset(test, clk_hw_unregister_divider_wrapper,
+						  div_hw));
+
+	/*
+	 * ULONG_MAX is the canonical way to probe the maximum rate a clock
+	 * can produce.
+	 */
+	rate = clk_hw_round_rate(div_hw, ULONG_MAX);
+	KUNIT_EXPECT_EQ(test, rate, PARENT_RATE_1GHZ / 2);
+}
+
+/*
+ * Test that clk_round_rate(clk, ULONG_MAX) returns the correct maximum rate
+ * when a mux clock sits between a divider and its parent candidates.
+ *
+ * Topology:
+ *
+ *   [fixed 4 GHz] --\
+ *                    +--> [mux CLK_SET_RATE_PARENT] --> [div {2,4,8} CLK_SET_RATE_PARENT]
+ *   [fixed 2 GHz] --/
+ *
+ */
+static void clk_divider_bestdiv_mux_ulong_max_returns_max_rate(struct kunit *test)
+{
+	static const char * const mux_parents[] = {
+		"bestdiv-mux-parent-a",
+		"bestdiv-mux-parent-b",
+	};
+	struct clk_hw *parent_a_hw, *parent_b_hw, *mux_hw, *div_hw;
+	u32 *fake_reg_mux, *fake_reg_div;
+	unsigned long rate;
+
+	fake_reg_mux = kunit_kzalloc(test, sizeof(*fake_reg_mux), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, fake_reg_mux);
+
+	fake_reg_div = kunit_kzalloc(test, sizeof(*fake_reg_div), GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, fake_reg_div);
+
+	/* Higher-rate parent: the mux should select this for ULONG_MAX. */
+	parent_a_hw = clk_hw_register_fixed_rate(NULL, "bestdiv-mux-parent-a",
+						 NULL, 0, PARENT_RATE_4GHZ);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, parent_a_hw);
+	KUNIT_ASSERT_EQ(test, 0,
+			kunit_add_action_or_reset(test, clk_hw_unregister_fixed_rate_wrapper,
+						  parent_a_hw));
+
+	/* Lower-rate parent: should not be selected. */
+	parent_b_hw = clk_hw_register_fixed_rate(NULL, "bestdiv-mux-parent-b",
+						 NULL, 0, PARENT_RATE_2GHZ);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, parent_b_hw);
+	KUNIT_ASSERT_EQ(test, 0,
+			kunit_add_action_or_reset(test, clk_hw_unregister_fixed_rate_wrapper,
+						  parent_b_hw));
+
+	/*
+	 * 1-bit mux register selects between the two parents.
+	 * CLK_SET_RATE_PARENT allows the divider's rate request to
+	 * propagate into clk_mux_determine_rate().
+	 */
+	mux_hw = clk_hw_register_mux(NULL, "bestdiv-mux",
+				     mux_parents, ARRAY_SIZE(mux_parents),
+				     CLK_SET_RATE_PARENT,
+				     (void __iomem __force *)fake_reg_mux,
+				     0, 1, 0, NULL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, mux_hw);
+	KUNIT_ASSERT_EQ(test, 0,
+			kunit_add_action_or_reset(test, clk_hw_unregister_mux_wrapper,
+						  mux_hw));
+
+	div_hw = clk_hw_register_divider_table(NULL, "bestdiv-mux-div",
+					       "bestdiv-mux",
+					       CLK_SET_RATE_PARENT,
+					       (void __iomem __force *)fake_reg_div,
+					       0, 2, 0, bestdiv_table, NULL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, div_hw);
+	KUNIT_ASSERT_EQ(test, 0,
+			kunit_add_action_or_reset(test, clk_hw_unregister_divider_wrapper,
+						  div_hw));
+
+	rate = clk_hw_round_rate(div_hw, ULONG_MAX);
+	KUNIT_EXPECT_EQ(test, rate, PARENT_RATE_4GHZ / 2);
+}
+
+static struct kunit_case clk_divider_bestdiv_test_cases[] = {
+	KUNIT_CASE(clk_divider_bestdiv_ulong_max_returns_max_rate),
+	KUNIT_CASE(clk_divider_bestdiv_mux_ulong_max_returns_max_rate),
+	{}
+};
+
+static struct kunit_suite clk_divider_bestdiv_test_suite = {
+	.name = "clk_divider_bestdiv",
+	.test_cases = clk_divider_bestdiv_test_cases,
+};
+
+kunit_test_suite(clk_divider_bestdiv_test_suite);
+
+MODULE_DESCRIPTION("KUnit tests for clk divider");
+MODULE_LICENSE("GPL");