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, 98 insertions, 0 deletions

diff --git a/drivers/mfd/da9055-i2c.c b/drivers/mfd/da9055-i2c.c
new file mode 100644
index 000000000..6c1981832
--- /dev/null
+++ b/drivers/mfd/da9055-i2c.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+ /* I2C access for DA9055 PMICs.
+ *
+ * Copyright(c) 2012 Dialog Semiconductor Ltd.
+ *
+ * Author: David Dajun Chen <dchen@diasemi.com>
+ */
+
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/i2c.h>
+#include <linux/err.h>
+#include <linux/of.h>
+
+#include <linux/mfd/da9055/core.h>
+
+static int da9055_i2c_probe(struct i2c_client *i2c)
+{
+	struct da9055 *da9055;
+	int ret;
+
+	da9055 = devm_kzalloc(&i2c->dev, sizeof(struct da9055), GFP_KERNEL);
+	if (!da9055)
+		return -ENOMEM;
+
+	da9055->regmap = devm_regmap_init_i2c(i2c, &da9055_regmap_config);
+	if (IS_ERR(da9055->regmap)) {
+		ret = PTR_ERR(da9055->regmap);
+		dev_err(&i2c->dev, "Failed to allocate register map: %d\n",
+			ret);
+		return ret;
+	}
+
+	da9055->dev = &i2c->dev;
+	da9055->chip_irq = i2c->irq;
+
+	i2c_set_clientdata(i2c, da9055);
+
+	return da9055_device_init(da9055);
+}
+
+static void da9055_i2c_remove(struct i2c_client *i2c)
+{
+	struct da9055 *da9055 = i2c_get_clientdata(i2c);
+
+	da9055_device_exit(da9055);
+}
+
+/*
+ * DO NOT change the device Ids. The naming is intentionally specific as both
+ * the PMIC and CODEC parts of this chip are instantiated separately as I2C
+ * devices (both have configurable I2C addresses, and are to all intents and
+ * purposes separate). As a result there are specific DA9055 ids for PMIC
+ * and CODEC, which must be different to operate together.
+ */
+static const struct i2c_device_id da9055_i2c_id[] = {
+	{ "da9055-pmic" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, da9055_i2c_id);
+
+static const struct of_device_id da9055_of_match[] = {
+	{ .compatible = "dlg,da9055-pmic", },
+	{ }
+};
+
+static struct i2c_driver da9055_i2c_driver = {
+	.probe = da9055_i2c_probe,
+	.remove = da9055_i2c_remove,
+	.id_table = da9055_i2c_id,
+	.driver = {
+		.name = "da9055-pmic",
+		.of_match_table = da9055_of_match,
+	},
+};
+
+static int __init da9055_i2c_init(void)
+{
+	int ret;
+
+	ret = i2c_add_driver(&da9055_i2c_driver);
+	if (ret != 0) {
+		pr_err("DA9055 I2C registration failed %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+subsys_initcall(da9055_i2c_init);
+
+static void __exit da9055_i2c_exit(void)
+{
+	i2c_del_driver(&da9055_i2c_driver);
+}
+module_exit(da9055_i2c_exit);
+
+MODULE_AUTHOR("David Dajun Chen <dchen@diasemi.com>");
+MODULE_DESCRIPTION("I2C driver for Dialog DA9055 PMIC");