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, 221 insertions, 0 deletions

diff --git a/drivers/hwmon/ltc4222.c b/drivers/hwmon/ltc4222.c
new file mode 100644
index 000000000..4fc69be5f
--- /dev/null
+++ b/drivers/hwmon/ltc4222.c
@@ -0,0 +1,221 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Driver for Linear Technology LTC4222 Dual Hot Swap controller
+ *
+ * Copyright (c) 2014 Guenter Roeck
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/bitops.h>
+#include <linux/i2c.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/jiffies.h>
+#include <linux/regmap.h>
+
+/* chip registers */
+
+#define LTC4222_CONTROL1	0xd0
+#define LTC4222_ALERT1		0xd1
+#define LTC4222_STATUS1		0xd2
+#define LTC4222_FAULT1		0xd3
+#define LTC4222_CONTROL2	0xd4
+#define LTC4222_ALERT2		0xd5
+#define LTC4222_STATUS2		0xd6
+#define LTC4222_FAULT2		0xd7
+#define LTC4222_SOURCE1		0xd8
+#define LTC4222_SOURCE2		0xda
+#define LTC4222_ADIN1		0xdc
+#define LTC4222_ADIN2		0xde
+#define LTC4222_SENSE1		0xe0
+#define LTC4222_SENSE2		0xe2
+#define LTC4222_ADC_CONTROL	0xe4
+
+/*
+ * Fault register bits
+ */
+#define FAULT_OV	BIT(0)
+#define FAULT_UV	BIT(1)
+#define FAULT_OC	BIT(2)
+#define FAULT_POWER_BAD	BIT(3)
+#define FAULT_FET_BAD	BIT(5)
+
+/* Return the voltage from the given register in mV or mA */
+static int ltc4222_get_value(struct device *dev, u8 reg)
+{
+	struct regmap *regmap = dev_get_drvdata(dev);
+	unsigned int val;
+	u8 buf[2];
+	int ret;
+
+	ret = regmap_bulk_read(regmap, reg, buf, 2);
+	if (ret < 0)
+		return ret;
+
+	val = ((buf[0] << 8) + buf[1]) >> 6;
+
+	switch (reg) {
+	case LTC4222_ADIN1:
+	case LTC4222_ADIN2:
+		/* 1.25 mV resolution. Convert to mV. */
+		val = DIV_ROUND_CLOSEST(val * 5, 4);
+		break;
+	case LTC4222_SOURCE1:
+	case LTC4222_SOURCE2:
+		/* 31.25 mV resolution. Convert to mV. */
+		val = DIV_ROUND_CLOSEST(val * 125, 4);
+		break;
+	case LTC4222_SENSE1:
+	case LTC4222_SENSE2:
+		/*
+		 * 62.5 uV resolution. Convert to current as measured with
+		 * an 1 mOhm sense resistor, in mA. If a different sense
+		 * resistor is installed, calculate the actual current by
+		 * dividing the reported current by the sense resistor value
+		 * in mOhm.
+		 */
+		val = DIV_ROUND_CLOSEST(val * 125, 2);
+		break;
+	default:
+		return -EINVAL;
+	}
+	return val;
+}
+
+static ssize_t ltc4222_value_show(struct device *dev,
+				  struct device_attribute *da, char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+	int value;
+
+	value = ltc4222_get_value(dev, attr->index);
+	if (value < 0)
+		return value;
+	return sysfs_emit(buf, "%d\n", value);
+}
+
+static ssize_t ltc4222_bool_show(struct device *dev,
+				 struct device_attribute *da, char *buf)
+{
+	struct sensor_device_attribute_2 *attr = to_sensor_dev_attr_2(da);
+	struct regmap *regmap = dev_get_drvdata(dev);
+	unsigned int fault;
+	int ret;
+
+	ret = regmap_read(regmap, attr->nr, &fault);
+	if (ret < 0)
+		return ret;
+	fault &= attr->index;
+	if (fault)		/* Clear reported faults in chip register */
+		regmap_update_bits(regmap, attr->nr, attr->index, 0);
+
+	return sysfs_emit(buf, "%d\n", !!fault);
+}
+
+/* Voltages */
+static SENSOR_DEVICE_ATTR_RO(in1_input, ltc4222_value, LTC4222_SOURCE1);
+static SENSOR_DEVICE_ATTR_RO(in2_input, ltc4222_value, LTC4222_ADIN1);
+static SENSOR_DEVICE_ATTR_RO(in3_input, ltc4222_value, LTC4222_SOURCE2);
+static SENSOR_DEVICE_ATTR_RO(in4_input, ltc4222_value, LTC4222_ADIN2);
+
+/*
+ * Voltage alarms
+ * UV/OV faults are associated with the input voltage, and power bad and fet
+ * faults are associated with the output voltage.
+ */
+static SENSOR_DEVICE_ATTR_2_RO(in1_min_alarm, ltc4222_bool, LTC4222_FAULT1,
+			       FAULT_UV);
+static SENSOR_DEVICE_ATTR_2_RO(in1_max_alarm, ltc4222_bool, LTC4222_FAULT1,
+			       FAULT_OV);
+static SENSOR_DEVICE_ATTR_2_RO(in2_alarm, ltc4222_bool, LTC4222_FAULT1,
+			       FAULT_POWER_BAD | FAULT_FET_BAD);
+
+static SENSOR_DEVICE_ATTR_2_RO(in3_min_alarm, ltc4222_bool, LTC4222_FAULT2,
+			       FAULT_UV);
+static SENSOR_DEVICE_ATTR_2_RO(in3_max_alarm, ltc4222_bool, LTC4222_FAULT2,
+			       FAULT_OV);
+static SENSOR_DEVICE_ATTR_2_RO(in4_alarm, ltc4222_bool, LTC4222_FAULT2,
+			       FAULT_POWER_BAD | FAULT_FET_BAD);
+
+/* Current (via sense resistor) */
+static SENSOR_DEVICE_ATTR_RO(curr1_input, ltc4222_value, LTC4222_SENSE1);
+static SENSOR_DEVICE_ATTR_RO(curr2_input, ltc4222_value, LTC4222_SENSE2);
+
+/* Overcurrent alarm */
+static SENSOR_DEVICE_ATTR_2_RO(curr1_max_alarm, ltc4222_bool, LTC4222_FAULT1,
+			       FAULT_OC);
+static SENSOR_DEVICE_ATTR_2_RO(curr2_max_alarm, ltc4222_bool, LTC4222_FAULT2,
+			       FAULT_OC);
+
+static struct attribute *ltc4222_attrs[] = {
+	&sensor_dev_attr_in1_input.dev_attr.attr,
+	&sensor_dev_attr_in1_min_alarm.dev_attr.attr,
+	&sensor_dev_attr_in1_max_alarm.dev_attr.attr,
+	&sensor_dev_attr_in2_input.dev_attr.attr,
+	&sensor_dev_attr_in2_alarm.dev_attr.attr,
+	&sensor_dev_attr_in3_input.dev_attr.attr,
+	&sensor_dev_attr_in3_min_alarm.dev_attr.attr,
+	&sensor_dev_attr_in3_max_alarm.dev_attr.attr,
+	&sensor_dev_attr_in4_input.dev_attr.attr,
+	&sensor_dev_attr_in4_alarm.dev_attr.attr,
+
+	&sensor_dev_attr_curr1_input.dev_attr.attr,
+	&sensor_dev_attr_curr1_max_alarm.dev_attr.attr,
+	&sensor_dev_attr_curr2_input.dev_attr.attr,
+	&sensor_dev_attr_curr2_max_alarm.dev_attr.attr,
+
+	NULL,
+};
+ATTRIBUTE_GROUPS(ltc4222);
+
+static const struct regmap_config ltc4222_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = LTC4222_ADC_CONTROL,
+};
+
+static int ltc4222_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct device *hwmon_dev;
+	struct regmap *regmap;
+
+	regmap = devm_regmap_init_i2c(client, &ltc4222_regmap_config);
+	if (IS_ERR(regmap)) {
+		dev_err(dev, "failed to allocate register map\n");
+		return PTR_ERR(regmap);
+	}
+
+	/* Clear faults */
+	regmap_write(regmap, LTC4222_FAULT1, 0x00);
+	regmap_write(regmap, LTC4222_FAULT2, 0x00);
+
+	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
+							   regmap,
+							   ltc4222_groups);
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id ltc4222_id[] = {
+	{ .name = "ltc4222" },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(i2c, ltc4222_id);
+
+static struct i2c_driver ltc4222_driver = {
+	.driver = {
+		   .name = "ltc4222",
+		   },
+	.probe = ltc4222_probe,
+	.id_table = ltc4222_id,
+};
+
+module_i2c_driver(ltc4222_driver);
+
+MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>");
+MODULE_DESCRIPTION("LTC4222 driver");
+MODULE_LICENSE("GPL");