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, 211 insertions, 0 deletions

diff --git a/drivers/iio/dac/max517.c b/drivers/iio/dac/max517.c
new file mode 100644
index 000000000..d2ddc72e0
--- /dev/null
+++ b/drivers/iio/dac/max517.c
@@ -0,0 +1,211 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  max517.c - Support for Maxim MAX517, MAX518 and MAX519
+ *
+ *  Copyright (C) 2010, 2011 Roland Stigge <stigge@antcom.de>
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/jiffies.h>
+#include <linux/i2c.h>
+#include <linux/err.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/iio/dac/max517.h>
+
+/* Commands */
+#define COMMAND_CHANNEL0	0x00
+#define COMMAND_CHANNEL1	0x01 /* for MAX518 and MAX519 */
+#define COMMAND_PD		0x08 /* Power Down */
+
+enum max517_device_ids {
+	ID_MAX517,
+	ID_MAX518,
+	ID_MAX519,
+	ID_MAX520,
+	ID_MAX521,
+};
+
+struct max517_data {
+	struct i2c_client	*client;
+	unsigned short		vref_mv[8];
+};
+
+/*
+ * channel: bit 0: channel 1
+ *          bit 1: channel 2
+ * (this way, it's possible to set both channels at once)
+ */
+static int max517_set_value(struct iio_dev *indio_dev,
+	long val, int channel)
+{
+	struct max517_data *data = iio_priv(indio_dev);
+	struct i2c_client *client = data->client;
+	u8 outbuf[2];
+	int res;
+
+	if (val < 0 || val > 255)
+		return -EINVAL;
+
+	outbuf[0] = channel;
+	outbuf[1] = val;
+
+	res = i2c_master_send(client, outbuf, 2);
+	if (res < 0)
+		return res;
+	else if (res != 2)
+		return -EIO;
+	else
+		return 0;
+}
+
+static int max517_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val,
+			   int *val2,
+			   long m)
+{
+	struct max517_data *data = iio_priv(indio_dev);
+
+	switch (m) {
+	case IIO_CHAN_INFO_SCALE:
+		/* Corresponds to Vref / 2^(bits) */
+		*val = data->vref_mv[chan->channel];
+		*val2 = 8;
+		return IIO_VAL_FRACTIONAL_LOG2;
+	default:
+		break;
+	}
+	return -EINVAL;
+}
+
+static int max517_write_raw(struct iio_dev *indio_dev,
+	struct iio_chan_spec const *chan, int val, int val2, long mask)
+{
+	int ret;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = max517_set_value(indio_dev, val, chan->channel);
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	return ret;
+}
+
+static int max517_suspend(struct device *dev)
+{
+	u8 outbuf = COMMAND_PD;
+
+	return i2c_master_send(to_i2c_client(dev), &outbuf, 1);
+}
+
+static int max517_resume(struct device *dev)
+{
+	u8 outbuf = 0;
+
+	return i2c_master_send(to_i2c_client(dev), &outbuf, 1);
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(max517_pm_ops, max517_suspend, max517_resume);
+
+static const struct iio_info max517_info = {
+	.read_raw = max517_read_raw,
+	.write_raw = max517_write_raw,
+};
+
+#define MAX517_CHANNEL(chan) {				\
+	.type = IIO_VOLTAGE,				\
+	.indexed = 1,					\
+	.output = 1,					\
+	.channel = (chan),				\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |	\
+	BIT(IIO_CHAN_INFO_SCALE),			\
+}
+
+static const struct iio_chan_spec max517_channels[] = {
+	MAX517_CHANNEL(0),
+	MAX517_CHANNEL(1),
+	MAX517_CHANNEL(2),
+	MAX517_CHANNEL(3),
+	MAX517_CHANNEL(4),
+	MAX517_CHANNEL(5),
+	MAX517_CHANNEL(6),
+	MAX517_CHANNEL(7),
+};
+
+static int max517_probe(struct i2c_client *client)
+{
+	const struct max517_platform_data *platform_data = dev_get_platdata(&client->dev);
+	const struct i2c_device_id *id = i2c_client_get_device_id(client);
+	struct max517_data *data;
+	struct iio_dev *indio_dev;
+	int chan;
+
+	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+	data = iio_priv(indio_dev);
+	data->client = client;
+
+	switch (id->driver_data) {
+	case ID_MAX521:
+		indio_dev->num_channels = 8;
+		break;
+	case ID_MAX520:
+		indio_dev->num_channels = 4;
+		break;
+	case ID_MAX519:
+	case ID_MAX518:
+		indio_dev->num_channels = 2;
+		break;
+	default:  /* single channel for MAX517 */
+		indio_dev->num_channels = 1;
+		break;
+	}
+	indio_dev->channels = max517_channels;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->info = &max517_info;
+
+	/*
+	 * Reference voltage on MAX518 and default is 5V, else take vref_mv
+	 * from platform_data
+	 */
+	for (chan = 0; chan < indio_dev->num_channels; chan++) {
+		if (id->driver_data == ID_MAX518 || !platform_data)
+			data->vref_mv[chan] = 5000; /* mV */
+		else
+			data->vref_mv[chan] = platform_data->vref_mv[chan];
+	}
+
+	return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id max517_id[] = {
+	{ .name = "max517", .driver_data = ID_MAX517 },
+	{ .name = "max518", .driver_data = ID_MAX518 },
+	{ .name = "max519", .driver_data = ID_MAX519 },
+	{ .name = "max520", .driver_data = ID_MAX520 },
+	{ .name = "max521", .driver_data = ID_MAX521 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, max517_id);
+
+static struct i2c_driver max517_driver = {
+	.driver = {
+		.name	= "max517",
+		.pm	= pm_sleep_ptr(&max517_pm_ops),
+	},
+	.probe		= max517_probe,
+	.id_table	= max517_id,
+};
+module_i2c_driver(max517_driver);
+
+MODULE_AUTHOR("Roland Stigge <stigge@antcom.de>");
+MODULE_DESCRIPTION("MAX517/518/519/520/521 8-bit DAC");
+MODULE_LICENSE("GPL");