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, 350 insertions, 0 deletions

diff --git a/drivers/hwmon/htu31.c b/drivers/hwmon/htu31.c
new file mode 100644
index 000000000..5d2cdbdb7
--- /dev/null
+++ b/drivers/hwmon/htu31.c
@@ -0,0 +1,350 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * The driver for Measurement Specialties HTU31 Temperature and Humidity sensor.
+ *
+ * Copyright (C) 2025
+ * Author: Andrei Lalaev <andrey.lalaev@gmail.com>
+ */
+
+#include <linux/array_size.h>
+#include <linux/cleanup.h>
+#include <linux/crc8.h>
+#include <linux/debugfs.h>
+#include <linux/delay.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/module.h>
+
+#define HTU31_READ_TEMP_HUM_CMD	0x00
+#define HTU31_READ_SERIAL_CMD		0x0a
+#define HTU31_CONVERSION_CMD		0x5e
+#define HTU31_HEATER_OFF_CMD		0x02
+#define HTU31_HEATER_ON_CMD		0x04
+
+#define HTU31_TEMP_HUM_LEN		6
+
+/* Conversion time for the highest resolution */
+#define HTU31_HUMIDITY_CONV_TIME	10000 /* us */
+#define HTU31_TEMPERATURE_CONV_TIME	15000 /* us */
+
+#define HTU31_SERIAL_NUMBER_LEN	3
+#define HTU31_SERIAL_NUMBER_CRC_LEN	1
+#define HTU31_SERIAL_NUMBER_CRC_OFFSET	3
+
+#define HTU31_CRC8_INIT_VAL		0
+#define HTU31_CRC8_POLYNOMIAL		0x31
+DECLARE_CRC8_TABLE(htu31_crc8_table);
+
+/**
+ * struct htu31_data - all the data required to operate a HTU31 chip
+ * @client: the i2c client associated with the HTU31
+ * @lock: a mutex to prevent parallel access to the data
+ * @wait_time: the time needed by sensor to convert values
+ * @temperature: the latest temperature value in millidegrees
+ * @humidity: the latest relative humidity value in millipercent
+ * @serial_number: the serial number of the sensor
+ * @heater_enable: the internal state of the heater
+ */
+struct htu31_data {
+	struct i2c_client *client;
+	struct mutex lock; /* Used to protect against parallel data updates */
+	long wait_time;
+	long temperature;
+	long humidity;
+	u8 serial_number[HTU31_SERIAL_NUMBER_LEN];
+	bool heater_enable;
+};
+
+static long htu31_temp_to_millicelsius(u16 val)
+{
+	return -40000 + DIV_ROUND_CLOSEST_ULL(165000ULL * val, 65535);
+}
+
+static long htu31_relative_humidity(u16 val)
+{
+	return DIV_ROUND_CLOSEST_ULL(100000ULL * val, 65535);
+}
+
+static int htu31_data_fetch_command(struct htu31_data *data)
+{
+	struct i2c_client *client = data->client;
+	u8 conversion_on = HTU31_CONVERSION_CMD;
+	u8 read_data_cmd = HTU31_READ_TEMP_HUM_CMD;
+	u8 t_h_buf[HTU31_TEMP_HUM_LEN] = {};
+	struct i2c_msg msgs[] = {
+		{
+			.addr = client->addr,
+			.flags = 0,
+			.len = 1,
+			.buf = &read_data_cmd,
+		},
+		{
+			.addr = client->addr,
+			.flags = I2C_M_RD,
+			.len = sizeof(t_h_buf),
+			.buf = t_h_buf,
+		},
+	};
+	int ret;
+	u8 crc;
+
+	guard(mutex)(&data->lock);
+
+	ret = i2c_master_send(client, &conversion_on, 1);
+	if (ret != 1) {
+		ret = ret < 0 ? ret : -EIO;
+		dev_err(&client->dev,
+			"Conversion command is failed. Error code: %d\n", ret);
+		return ret;
+	}
+
+	fsleep(data->wait_time);
+
+	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
+	if (ret != ARRAY_SIZE(msgs)) {
+		ret = ret < 0 ? ret : -EIO;
+		dev_err(&client->dev,
+			"T&H command is failed. Error code: %d\n", ret);
+		return ret;
+	}
+
+	crc = crc8(htu31_crc8_table, &t_h_buf[0], 2, HTU31_CRC8_INIT_VAL);
+	if (crc != t_h_buf[2]) {
+		dev_err(&client->dev, "Temperature CRC mismatch\n");
+		return -EIO;
+	}
+
+	crc = crc8(htu31_crc8_table, &t_h_buf[3], 2, HTU31_CRC8_INIT_VAL);
+	if (crc != t_h_buf[5]) {
+		dev_err(&client->dev, "Humidity CRC mismatch\n");
+		return -EIO;
+	}
+
+	data->temperature = htu31_temp_to_millicelsius(be16_to_cpup((__be16 *)&t_h_buf[0]));
+	data->humidity = htu31_relative_humidity(be16_to_cpup((__be16 *)&t_h_buf[3]));
+
+	return 0;
+}
+
+static umode_t htu31_is_visible(const void *data, enum hwmon_sensor_types type,
+				u32 attr, int channel)
+{
+	switch (type) {
+	case hwmon_temp:
+	case hwmon_humidity:
+		return 0444;
+	default:
+		return 0;
+	}
+}
+
+static int htu31_read(struct device *dev, enum hwmon_sensor_types type,
+		      u32 attr, int channel, long *val)
+{
+	struct htu31_data *data = dev_get_drvdata(dev);
+	int ret;
+
+	ret = htu31_data_fetch_command(data);
+	if (ret < 0)
+		return ret;
+
+	switch (type) {
+	case hwmon_temp:
+		if (attr != hwmon_temp_input)
+			return -EINVAL;
+
+		*val = data->temperature;
+		break;
+	case hwmon_humidity:
+		if (attr != hwmon_humidity_input)
+			return -EINVAL;
+
+		*val = data->humidity;
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+static int htu31_read_serial_number(struct htu31_data *data)
+{
+	struct i2c_client *client = data->client;
+	u8 read_sn_cmd = HTU31_READ_SERIAL_CMD;
+	u8 sn_buf[HTU31_SERIAL_NUMBER_LEN + HTU31_SERIAL_NUMBER_CRC_LEN];
+	struct i2c_msg msgs[] = {
+		{
+			.addr = client->addr,
+			.flags = 0,
+			.len = 1,
+			.buf = &read_sn_cmd,
+		},
+		{
+			.addr = client->addr,
+			.flags = I2C_M_RD,
+			.len = sizeof(sn_buf),
+			.buf = sn_buf,
+		},
+	};
+	int ret;
+	u8 crc;
+
+	ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
+	if (ret < 0)
+		return ret;
+
+	crc = crc8(htu31_crc8_table, sn_buf, HTU31_SERIAL_NUMBER_LEN, HTU31_CRC8_INIT_VAL);
+	if (crc != sn_buf[HTU31_SERIAL_NUMBER_CRC_OFFSET]) {
+		dev_err(&client->dev, "Serial number CRC mismatch\n");
+		return -EIO;
+	}
+
+	memcpy(data->serial_number, sn_buf, HTU31_SERIAL_NUMBER_LEN);
+
+	return 0;
+}
+
+static ssize_t heater_enable_show(struct device *dev,
+				  struct device_attribute *attr,
+				  char *buf)
+{
+	struct htu31_data *data = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%d\n", data->heater_enable);
+}
+
+static ssize_t heater_enable_store(struct device *dev,
+				   struct device_attribute *attr,
+				   const char *buf,
+				   size_t count)
+{
+	struct htu31_data *data = dev_get_drvdata(dev);
+	u8 heater_cmd;
+	bool status;
+	int ret;
+
+	ret = kstrtobool(buf, &status);
+	if (ret)
+		return ret;
+
+	heater_cmd = status ? HTU31_HEATER_ON_CMD : HTU31_HEATER_OFF_CMD;
+
+	guard(mutex)(&data->lock);
+
+	ret = i2c_master_send(data->client, &heater_cmd, 1);
+	if (ret < 0)
+		return ret;
+
+	data->heater_enable = status;
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(heater_enable);
+
+static int serial_number_show(struct seq_file *seq_file,
+			      void *unused)
+{
+	struct htu31_data *data = seq_file->private;
+
+	seq_printf(seq_file, "%X%X%X\n", data->serial_number[0],
+		   data->serial_number[1], data->serial_number[2]);
+	return 0;
+}
+
+DEFINE_SHOW_ATTRIBUTE(serial_number);
+
+static struct attribute *htu31_attrs[] = {
+	&dev_attr_heater_enable.attr,
+	NULL
+};
+
+ATTRIBUTE_GROUPS(htu31);
+
+static const struct hwmon_channel_info * const htu31_info[] = {
+	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
+	HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT),
+	NULL
+};
+
+static const struct hwmon_ops htu31_hwmon_ops = {
+	.is_visible = htu31_is_visible,
+	.read = htu31_read,
+};
+
+static const struct hwmon_chip_info htu31_chip_info = {
+	.info = htu31_info,
+	.ops = &htu31_hwmon_ops,
+};
+
+static int htu31_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct device *hwmon_dev;
+	struct htu31_data *data;
+	int ret;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->client = client;
+	data->wait_time = HTU31_TEMPERATURE_CONV_TIME + HTU31_HUMIDITY_CONV_TIME;
+
+	ret = devm_mutex_init(dev, &data->lock);
+	if (ret)
+		return ret;
+
+	crc8_populate_msb(htu31_crc8_table, HTU31_CRC8_POLYNOMIAL);
+
+	ret = htu31_read_serial_number(data);
+	if (ret) {
+		dev_err(dev, "Failed to read serial number\n");
+		return ret;
+	}
+
+	debugfs_create_file("serial_number",
+			    0444,
+			    client->debugfs,
+			    data,
+			    &serial_number_fops);
+
+	hwmon_dev = devm_hwmon_device_register_with_info(dev,
+							 client->name,
+							 data,
+							 &htu31_chip_info,
+							 htu31_groups);
+
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id htu31_id[] = {
+	{ .name = "htu31" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, htu31_id);
+
+#if IS_ENABLED(CONFIG_OF)
+static const struct of_device_id htu31_of_match[] = {
+	{ .compatible = "meas,htu31" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, htu31_of_match);
+#endif
+
+static struct i2c_driver htu31_driver = {
+	.driver = {
+		.name = "htu31",
+		.of_match_table = of_match_ptr(htu31_of_match),
+	},
+	.probe = htu31_probe,
+	.id_table = htu31_id,
+};
+module_i2c_driver(htu31_driver);
+
+MODULE_AUTHOR("Andrei Lalaev <andrey.lalaev@gmail.com>");
+MODULE_DESCRIPTION("HTU31 Temperature and Humidity sensor driver");
+MODULE_LICENSE("GPL");