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, 234 insertions, 0 deletions

diff --git a/drivers/hwmon/hs3001.c b/drivers/hwmon/hs3001.c
new file mode 100644
index 000000000..b263cbeca
--- /dev/null
+++ b/drivers/hwmon/hs3001.c
@@ -0,0 +1,234 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * This is a non-complete driver implementation for the
+ * HS3001 humidity and temperature sensor and compatibles. It does not include
+ * the configuration possibilities, where it needs to be set to 'programming mode'
+ * during power-up.
+ *
+ *
+ * Copyright (C) 2023 SYS TEC electronic AG
+ * Author: Andre Werner <andre.werner@systec-electronic.com>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/hwmon.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+
+/* Measurement times */
+#define HS3001_WAKEUP_TIME	100	/* us */
+#define HS3001_8BIT_RESOLUTION	550	/* us */
+#define HS3001_10BIT_RESOLUTION	1310	/* us */
+#define HS3001_12BIT_RESOLUTION	4500	/* us */
+#define HS3001_14BIT_RESOLUTION	16900	/* us */
+
+#define HS3001_RESPONSE_LENGTH	4
+
+#define HS3001_FIXPOINT_ARITH	1000U
+
+#define HS3001_MASK_HUMIDITY_0X3FFF	GENMASK(13, 0)
+#define HS3001_MASK_STATUS_0XC0	GENMASK(7, 6)
+
+/* Definitions for Status Bits of A/D Data */
+#define HS3001_DATA_VALID	0x00	/* Valid Data */
+#define HS3001_DATA_STALE	0x01	/* Stale Data */
+
+struct hs3001_data {
+	struct i2c_client *client;
+	u32 wait_time;		/* in us */
+	int temperature;	/* in milli degree */
+	u32 humidity;		/* in milli % */
+};
+
+static int hs3001_extract_temperature(u16 raw)
+{
+	/* fixpoint arithmetic 1 digit */
+	u32 temp = (raw >> 2) * HS3001_FIXPOINT_ARITH * 165;
+
+	temp /= (1 << 14) - 1;
+
+	return (int)temp - 40 * HS3001_FIXPOINT_ARITH;
+}
+
+static u32 hs3001_extract_humidity(u16 raw)
+{
+	u32 hum = (raw & HS3001_MASK_HUMIDITY_0X3FFF) * HS3001_FIXPOINT_ARITH * 100;
+
+	return hum / (1 << 14) - 1;
+}
+
+static int hs3001_data_fetch_command(struct i2c_client *client,
+				     struct hs3001_data *data)
+{
+	int ret;
+	u8 buf[HS3001_RESPONSE_LENGTH];
+	u8 hs3001_status;
+
+	ret = i2c_master_recv(client, buf, HS3001_RESPONSE_LENGTH);
+	if (ret != HS3001_RESPONSE_LENGTH) {
+		ret = ret < 0 ? ret : -EIO;
+		dev_dbg(&client->dev,
+			"Error in i2c communication. Error code: %d.\n", ret);
+		return ret;
+	}
+
+	hs3001_status = FIELD_GET(HS3001_MASK_STATUS_0XC0, buf[0]);
+	if (hs3001_status == HS3001_DATA_STALE) {
+		dev_dbg(&client->dev, "Sensor busy.\n");
+		return -EBUSY;
+	}
+	if (hs3001_status != HS3001_DATA_VALID) {
+		dev_dbg(&client->dev, "Data invalid.\n");
+		return -EIO;
+	}
+
+	data->humidity =
+		hs3001_extract_humidity(be16_to_cpup((__be16 *)&buf[0]));
+	data->temperature =
+		hs3001_extract_temperature(be16_to_cpup((__be16 *)&buf[2]));
+
+	return 0;
+}
+
+static umode_t hs3001_is_visible(const void *data, enum hwmon_sensor_types type,
+				 u32 attr, int channel)
+{
+	/* Both, humidity and temperature can only be read. */
+	return 0444;
+}
+
+static int hs3001_read(struct device *dev, enum hwmon_sensor_types type,
+		       u32 attr, int channel, long *val)
+{
+	struct hs3001_data *data = dev_get_drvdata(dev);
+	struct i2c_client *client = data->client;
+	int ret;
+
+	ret = i2c_master_send(client, NULL, 0);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * Sensor needs some time to process measurement depending on
+	 * resolution (ref. datasheet)
+	 */
+	fsleep(data->wait_time);
+
+	ret = hs3001_data_fetch_command(client, data);
+	if (ret < 0)
+		return ret;
+
+	switch (type) {
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_input:
+			*val = data->temperature;
+			break;
+		default:
+			return -EINVAL;
+		}
+		break;
+	case hwmon_humidity:
+		switch (attr) {
+		case hwmon_humidity_input:
+			*val = data->humidity;
+			break;
+		default:
+			return -EINVAL;
+		}
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct hwmon_channel_info *hs3001_info[] = {
+	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
+	HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT),
+	NULL
+};
+
+static const struct hwmon_ops hs3001_hwmon_ops = {
+	.is_visible = hs3001_is_visible,
+	.read = hs3001_read,
+};
+
+static const struct hwmon_chip_info hs3001_chip_info = {
+	.ops = &hs3001_hwmon_ops,
+	.info = hs3001_info,
+};
+
+/* device ID table */
+static const struct i2c_device_id hs3001_ids[] = {
+	{ .name = "hs3001" },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(i2c, hs3001_ids);
+
+static const struct of_device_id hs3001_of_match[] = {
+	{.compatible = "renesas,hs3001"},
+	{ },
+};
+
+MODULE_DEVICE_TABLE(of, hs3001_of_match);
+
+static int hs3001_probe(struct i2c_client *client)
+{
+	struct hs3001_data *data;
+	struct device *hwmon_dev;
+	struct device *dev = &client->dev;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -EOPNOTSUPP;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->client = client;
+
+	/*
+	 * Measurement time = wake-up time + measurement time temperature
+	 * + measurement time humidity. This is currently static, because
+	 * enabling programming mode is not supported, yet.
+	 */
+	data->wait_time = (HS3001_WAKEUP_TIME + HS3001_14BIT_RESOLUTION +
+			   HS3001_14BIT_RESOLUTION);
+
+	hwmon_dev = devm_hwmon_device_register_with_info(dev,
+							 client->name,
+							 data,
+							 &hs3001_chip_info,
+							 NULL);
+
+	if (IS_ERR(hwmon_dev))
+		return dev_err_probe(dev, PTR_ERR(hwmon_dev),
+				     "Unable to register hwmon device.\n");
+
+	return 0;
+}
+
+static struct i2c_driver hs3001_i2c_driver = {
+	.driver = {
+		   .name = "hs3001",
+		   .of_match_table = hs3001_of_match,
+	},
+	.probe = hs3001_probe,
+	.id_table = hs3001_ids,
+};
+
+module_i2c_driver(hs3001_i2c_driver);
+
+MODULE_AUTHOR("Andre Werner <andre.werner@systec-electronic.com>");
+MODULE_DESCRIPTION("HS3001 humidity and temperature sensor base driver");
+MODULE_LICENSE("GPL");