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, 87 insertions, 0 deletions

diff --git a/drivers/mfd/lp873x.c b/drivers/mfd/lp873x.c
new file mode 100644
index 000000000..d2c90302b
--- /dev/null
+++ b/drivers/mfd/lp873x.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2016 Texas Instruments Incorporated - https://www.ti.com/
+ *
+ * Author: Keerthy <j-keerthy@ti.com>
+ */
+
+#include <linux/interrupt.h>
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#include <linux/mfd/lp873x.h>
+
+static const struct regmap_config lp873x_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = LP873X_REG_MAX,
+};
+
+static const struct mfd_cell lp873x_cells[] = {
+	{ .name = "lp873x-regulator", },
+	{ .name = "lp873x-gpio", },
+};
+
+static int lp873x_probe(struct i2c_client *client)
+{
+	struct lp873x *lp873;
+	int ret;
+	unsigned int otpid;
+
+	lp873 = devm_kzalloc(&client->dev, sizeof(*lp873), GFP_KERNEL);
+	if (!lp873)
+		return -ENOMEM;
+
+	lp873->dev = &client->dev;
+
+	lp873->regmap = devm_regmap_init_i2c(client, &lp873x_regmap_config);
+	if (IS_ERR(lp873->regmap)) {
+		ret = PTR_ERR(lp873->regmap);
+		dev_err(lp873->dev,
+			"Failed to initialize register map: %d\n", ret);
+		return ret;
+	}
+
+	ret = regmap_read(lp873->regmap, LP873X_REG_OTP_REV, &otpid);
+	if (ret) {
+		dev_err(lp873->dev, "Failed to read OTP ID\n");
+		return ret;
+	}
+
+	lp873->rev = otpid & LP873X_OTP_REV_OTP_ID;
+
+	i2c_set_clientdata(client, lp873);
+
+	ret = mfd_add_devices(lp873->dev, PLATFORM_DEVID_AUTO, lp873x_cells,
+			      ARRAY_SIZE(lp873x_cells), NULL, 0, NULL);
+
+	return ret;
+}
+
+static const struct of_device_id of_lp873x_match_table[] = {
+	{ .compatible = "ti,lp8733", },
+	{ .compatible = "ti,lp8732", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, of_lp873x_match_table);
+
+static const struct i2c_device_id lp873x_id_table[] = {
+	{ "lp873x" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, lp873x_id_table);
+
+static struct i2c_driver lp873x_driver = {
+	.driver	= {
+		.name	= "lp873x",
+		.of_match_table = of_lp873x_match_table,
+	},
+	.probe		= lp873x_probe,
+	.id_table	= lp873x_id_table,
+};
+module_i2c_driver(lp873x_driver);
+
+MODULE_AUTHOR("J Keerthy <j-keerthy@ti.com>");
+MODULE_DESCRIPTION("LP873X chip family Multi-Function Device driver");
+MODULE_LICENSE("GPL v2");