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, 279 insertions, 0 deletions

diff --git a/drivers/hwmon/ltc2990.c b/drivers/hwmon/ltc2990.c
new file mode 100644
index 000000000..a2725e4b2
--- /dev/null
+++ b/drivers/hwmon/ltc2990.c
@@ -0,0 +1,279 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Driver for Linear Technology LTC2990 power monitor
+ *
+ * Copyright (C) 2014 Topic Embedded Products
+ * Author: Mike Looijmans <mike.looijmans@topic.nl>
+ */
+
+#include <linux/bitops.h>
+#include <linux/err.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/property.h>
+
+#define LTC2990_STATUS	0x00
+#define LTC2990_CONTROL	0x01
+#define LTC2990_TRIGGER	0x02
+#define LTC2990_TINT_MSB	0x04
+#define LTC2990_V1_MSB	0x06
+#define LTC2990_V2_MSB	0x08
+#define LTC2990_V3_MSB	0x0A
+#define LTC2990_V4_MSB	0x0C
+#define LTC2990_VCC_MSB	0x0E
+
+#define LTC2990_IN0	BIT(0)
+#define LTC2990_IN1	BIT(1)
+#define LTC2990_IN2	BIT(2)
+#define LTC2990_IN3	BIT(3)
+#define LTC2990_IN4	BIT(4)
+#define LTC2990_CURR1	BIT(5)
+#define LTC2990_CURR2	BIT(6)
+#define LTC2990_TEMP1	BIT(7)
+#define LTC2990_TEMP2	BIT(8)
+#define LTC2990_TEMP3	BIT(9)
+#define LTC2990_NONE	0
+#define LTC2990_ALL	GENMASK(9, 0)
+
+#define LTC2990_MODE0_SHIFT	0
+#define LTC2990_MODE0_MASK	GENMASK(2, 0)
+#define LTC2990_MODE1_SHIFT	3
+#define LTC2990_MODE1_MASK	GENMASK(1, 0)
+
+/* Enabled measurements for mode bits 2..0 */
+static const int ltc2990_attrs_ena_0[] = {
+	LTC2990_IN1 | LTC2990_IN2 | LTC2990_TEMP3,
+	LTC2990_CURR1 | LTC2990_TEMP3,
+	LTC2990_CURR1 | LTC2990_IN3 | LTC2990_IN4,
+	LTC2990_TEMP2 | LTC2990_IN3 | LTC2990_IN4,
+	LTC2990_TEMP2 | LTC2990_CURR2,
+	LTC2990_TEMP2 | LTC2990_TEMP3,
+	LTC2990_CURR1 | LTC2990_CURR2,
+	LTC2990_IN1 | LTC2990_IN2 | LTC2990_IN3 | LTC2990_IN4
+};
+
+/* Enabled measurements for mode bits 4..3 */
+static const int ltc2990_attrs_ena_1[] = {
+	LTC2990_NONE,
+	LTC2990_TEMP2 | LTC2990_IN1 | LTC2990_CURR1,
+	LTC2990_TEMP3 | LTC2990_IN3 | LTC2990_CURR2,
+	LTC2990_ALL
+};
+
+struct ltc2990_data {
+	struct i2c_client *i2c;
+	u32 mode[2];
+};
+
+/* Return the converted value from the given register in uV or mC */
+static int ltc2990_get_value(struct i2c_client *i2c, int index, int *result)
+{
+	int val;
+	u8 reg;
+
+	switch (index) {
+	case LTC2990_IN0:
+		reg = LTC2990_VCC_MSB;
+		break;
+	case LTC2990_IN1:
+	case LTC2990_CURR1:
+	case LTC2990_TEMP2:
+		reg = LTC2990_V1_MSB;
+		break;
+	case LTC2990_IN2:
+		reg = LTC2990_V2_MSB;
+		break;
+	case LTC2990_IN3:
+	case LTC2990_CURR2:
+	case LTC2990_TEMP3:
+		reg = LTC2990_V3_MSB;
+		break;
+	case LTC2990_IN4:
+		reg = LTC2990_V4_MSB;
+		break;
+	case LTC2990_TEMP1:
+		reg = LTC2990_TINT_MSB;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	val = i2c_smbus_read_word_swapped(i2c, reg);
+	if (unlikely(val < 0))
+		return val;
+
+	switch (index) {
+	case LTC2990_TEMP1:
+	case LTC2990_TEMP2:
+	case LTC2990_TEMP3:
+		/* temp, 0.0625 degrees/LSB */
+		*result = sign_extend32(val, 12) * 1000 / 16;
+		break;
+	case LTC2990_CURR1:
+	case LTC2990_CURR2:
+		 /* Vx-Vy, 19.42uV/LSB */
+		*result = sign_extend32(val, 14) * 1942 / 100;
+		break;
+	case LTC2990_IN0:
+		/* Vcc, 305.18uV/LSB, 2.5V offset */
+		*result = sign_extend32(val, 14) * 30518 / (100 * 1000) + 2500;
+		break;
+	case LTC2990_IN1:
+	case LTC2990_IN2:
+	case LTC2990_IN3:
+	case LTC2990_IN4:
+		/* Vx, 305.18uV/LSB */
+		*result = sign_extend32(val, 14) * 30518 / (100 * 1000);
+		break;
+	default:
+		return -EINVAL; /* won't happen, keep compiler happy */
+	}
+
+	return 0;
+}
+
+static ssize_t ltc2990_value_show(struct device *dev,
+				  struct device_attribute *da, char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+	struct ltc2990_data *data = dev_get_drvdata(dev);
+	int value;
+	int ret;
+
+	ret = ltc2990_get_value(data->i2c, attr->index, &value);
+	if (unlikely(ret < 0))
+		return ret;
+
+	return sysfs_emit(buf, "%d\n", value);
+}
+
+static umode_t ltc2990_attrs_visible(struct kobject *kobj,
+				     struct attribute *a, int n)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct ltc2990_data *data = dev_get_drvdata(dev);
+	struct device_attribute *da =
+			container_of(a, struct device_attribute, attr);
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+
+	int attrs_mask = LTC2990_IN0 | LTC2990_TEMP1 |
+			 (ltc2990_attrs_ena_0[data->mode[0]] &
+			  ltc2990_attrs_ena_1[data->mode[1]]);
+
+	if (attr->index & attrs_mask)
+		return a->mode;
+
+	return 0;
+}
+
+static SENSOR_DEVICE_ATTR_RO(temp1_input, ltc2990_value, LTC2990_TEMP1);
+static SENSOR_DEVICE_ATTR_RO(temp2_input, ltc2990_value, LTC2990_TEMP2);
+static SENSOR_DEVICE_ATTR_RO(temp3_input, ltc2990_value, LTC2990_TEMP3);
+static SENSOR_DEVICE_ATTR_RO(curr1_input, ltc2990_value, LTC2990_CURR1);
+static SENSOR_DEVICE_ATTR_RO(curr2_input, ltc2990_value, LTC2990_CURR2);
+static SENSOR_DEVICE_ATTR_RO(in0_input, ltc2990_value, LTC2990_IN0);
+static SENSOR_DEVICE_ATTR_RO(in1_input, ltc2990_value, LTC2990_IN1);
+static SENSOR_DEVICE_ATTR_RO(in2_input, ltc2990_value, LTC2990_IN2);
+static SENSOR_DEVICE_ATTR_RO(in3_input, ltc2990_value, LTC2990_IN3);
+static SENSOR_DEVICE_ATTR_RO(in4_input, ltc2990_value, LTC2990_IN4);
+
+static struct attribute *ltc2990_attrs[] = {
+	&sensor_dev_attr_temp1_input.dev_attr.attr,
+	&sensor_dev_attr_temp2_input.dev_attr.attr,
+	&sensor_dev_attr_temp3_input.dev_attr.attr,
+	&sensor_dev_attr_curr1_input.dev_attr.attr,
+	&sensor_dev_attr_curr2_input.dev_attr.attr,
+	&sensor_dev_attr_in0_input.dev_attr.attr,
+	&sensor_dev_attr_in1_input.dev_attr.attr,
+	&sensor_dev_attr_in2_input.dev_attr.attr,
+	&sensor_dev_attr_in3_input.dev_attr.attr,
+	&sensor_dev_attr_in4_input.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group ltc2990_group = {
+	.attrs = ltc2990_attrs,
+	.is_visible = ltc2990_attrs_visible,
+};
+__ATTRIBUTE_GROUPS(ltc2990);
+
+static int ltc2990_i2c_probe(struct i2c_client *i2c)
+{
+	int ret;
+	struct device *hwmon_dev;
+	struct ltc2990_data *data;
+
+	if (!i2c_check_functionality(i2c->adapter, I2C_FUNC_SMBUS_BYTE_DATA |
+				     I2C_FUNC_SMBUS_WORD_DATA))
+		return -ENODEV;
+
+	data = devm_kzalloc(&i2c->dev, sizeof(struct ltc2990_data), GFP_KERNEL);
+	if (unlikely(!data))
+		return -ENOMEM;
+
+	data->i2c = i2c;
+
+	if (dev_fwnode(&i2c->dev)) {
+		ret = device_property_read_u32_array(&i2c->dev,
+						     "lltc,meas-mode",
+						     data->mode, 2);
+		if (ret < 0)
+			return ret;
+
+		if (data->mode[0] & ~LTC2990_MODE0_MASK ||
+		    data->mode[1] & ~LTC2990_MODE1_MASK)
+			return -EINVAL;
+	} else {
+		ret = i2c_smbus_read_byte_data(i2c, LTC2990_CONTROL);
+		if (ret < 0)
+			return ret;
+
+		data->mode[0] = ret >> LTC2990_MODE0_SHIFT & LTC2990_MODE0_MASK;
+		data->mode[1] = ret >> LTC2990_MODE1_SHIFT & LTC2990_MODE1_MASK;
+	}
+
+	/* Setup continuous mode */
+	ret = i2c_smbus_write_byte_data(i2c, LTC2990_CONTROL,
+					data->mode[0] << LTC2990_MODE0_SHIFT |
+					data->mode[1] << LTC2990_MODE1_SHIFT);
+	if (ret < 0) {
+		dev_err(&i2c->dev, "Error: Failed to set control mode.\n");
+		return ret;
+	}
+	/* Trigger once to start continuous conversion */
+	ret = i2c_smbus_write_byte_data(i2c, LTC2990_TRIGGER, 1);
+	if (ret < 0) {
+		dev_err(&i2c->dev, "Error: Failed to start acquisition.\n");
+		return ret;
+	}
+
+	hwmon_dev = devm_hwmon_device_register_with_groups(&i2c->dev,
+							   i2c->name,
+							   data,
+							   ltc2990_groups);
+
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id ltc2990_i2c_id[] = {
+	{ .name = "ltc2990" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ltc2990_i2c_id);
+
+static struct i2c_driver ltc2990_i2c_driver = {
+	.driver = {
+		.name = "ltc2990",
+	},
+	.probe = ltc2990_i2c_probe,
+	.id_table = ltc2990_i2c_id,
+};
+
+module_i2c_driver(ltc2990_i2c_driver);
+
+MODULE_DESCRIPTION("LTC2990 Sensor Driver");
+MODULE_AUTHOR("Topic Embedded Products");
+MODULE_LICENSE("GPL v2");