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, 79 insertions, 0 deletions

diff --git a/drivers/mfd/mp2629.c b/drivers/mfd/mp2629.c
new file mode 100644
index 000000000..717b704c3
--- /dev/null
+++ b/drivers/mfd/mp2629.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * MP2629 parent driver for ADC and battery charger
+ *
+ * Copyright 2020 Monolithic Power Systems, Inc
+ *
+ * Author: Saravanan Sekar <sravanhome@gmail.com>
+ */
+
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/mp2629.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+static const struct mfd_cell mp2629_cell[] = {
+	{
+		.name = "mp2629_adc",
+		.of_compatible = "mps,mp2629_adc",
+	},
+	{
+		.name = "mp2629_charger",
+		.of_compatible = "mps,mp2629_charger",
+	}
+};
+
+static const struct regmap_config mp2629_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = 0x17,
+};
+
+static int mp2629_probe(struct i2c_client *client)
+{
+	struct mp2629_data *ddata;
+	int ret;
+
+	ddata = devm_kzalloc(&client->dev, sizeof(*ddata), GFP_KERNEL);
+	if (!ddata)
+		return -ENOMEM;
+
+	ddata->dev = &client->dev;
+	i2c_set_clientdata(client, ddata);
+
+	ddata->regmap = devm_regmap_init_i2c(client, &mp2629_regmap_config);
+	if (IS_ERR(ddata->regmap)) {
+		dev_err(ddata->dev, "Failed to allocate regmap\n");
+		return PTR_ERR(ddata->regmap);
+	}
+
+	ret = devm_mfd_add_devices(ddata->dev, PLATFORM_DEVID_AUTO, mp2629_cell,
+				   ARRAY_SIZE(mp2629_cell), NULL, 0, NULL);
+	if (ret)
+		dev_err(ddata->dev, "Failed to register sub-devices %d\n", ret);
+
+	return ret;
+}
+
+static const struct of_device_id mp2629_of_match[] = {
+	{ .compatible = "mps,mp2629"},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, mp2629_of_match);
+
+static struct i2c_driver mp2629_driver = {
+	.driver = {
+		.name = "mp2629",
+		.of_match_table = mp2629_of_match,
+	},
+	.probe		= mp2629_probe,
+};
+module_i2c_driver(mp2629_driver);
+
+MODULE_AUTHOR("Saravanan Sekar <sravanhome@gmail.com>");
+MODULE_DESCRIPTION("MP2629 Battery charger parent driver");
+MODULE_LICENSE("GPL");