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, 88 insertions, 0 deletions

diff --git a/drivers/mfd/sky81452.c b/drivers/mfd/sky81452.c
new file mode 100644
index 000000000..771b62a5c
--- /dev/null
+++ b/drivers/mfd/sky81452.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * sky81452.c	SKY81452 MFD driver
+ *
+ * Copyright 2014 Skyworks Solutions Inc.
+ * Author : Gyungoh Yoo <jack.yoo@skyworksinc.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/regmap.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/sky81452.h>
+
+static const struct regmap_config sky81452_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static int sky81452_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	const struct sky81452_platform_data *pdata = dev_get_platdata(dev);
+	struct mfd_cell cells[2];
+	struct regmap *regmap;
+	int ret;
+
+	if (!pdata) {
+		pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
+		if (!pdata)
+			return -ENOMEM;
+	}
+
+	regmap = devm_regmap_init_i2c(client, &sky81452_config);
+	if (IS_ERR(regmap)) {
+		dev_err(dev, "failed to initialize.err=%ld\n", PTR_ERR(regmap));
+		return PTR_ERR(regmap);
+	}
+
+	i2c_set_clientdata(client, regmap);
+
+	memset(cells, 0, sizeof(cells));
+	cells[0].name = "sky81452-backlight";
+	cells[0].of_compatible = "skyworks,sky81452-backlight";
+	cells[1].name = "sky81452-regulator";
+	cells[1].platform_data = pdata->regulator_init_data;
+	cells[1].pdata_size = sizeof(*pdata->regulator_init_data);
+
+	ret = devm_mfd_add_devices(dev, -1, cells, ARRAY_SIZE(cells),
+				   NULL, 0, NULL);
+	if (ret)
+		dev_err(dev, "failed to add child devices. err=%d\n", ret);
+
+	return ret;
+}
+
+static const struct i2c_device_id sky81452_ids[] = {
+	{ "sky81452" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, sky81452_ids);
+
+#ifdef CONFIG_OF
+static const struct of_device_id sky81452_of_match[] = {
+	{ .compatible = "skyworks,sky81452", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, sky81452_of_match);
+#endif
+
+static struct i2c_driver sky81452_driver = {
+	.driver = {
+		.name = "sky81452",
+		.of_match_table = of_match_ptr(sky81452_of_match),
+	},
+	.probe = sky81452_probe,
+	.id_table = sky81452_ids,
+};
+
+module_i2c_driver(sky81452_driver);
+
+MODULE_DESCRIPTION("Skyworks SKY81452 MFD driver");
+MODULE_AUTHOR("Gyungoh Yoo <jack.yoo@skyworksinc.com>");
+MODULE_LICENSE("GPL v2");