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, 130 insertions, 0 deletions

diff --git a/drivers/iio/resolver/ad2s90.c b/drivers/iio/resolver/ad2s90.c
new file mode 100644
index 000000000..b7a2dcc42
--- /dev/null
+++ b/drivers/iio/resolver/ad2s90.c
@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ad2s90.c simple support for the ADI Resolver to Digital Converters: AD2S90
+ *
+ * Copyright (c) 2010-2010 Analog Devices Inc.
+ */
+#include <linux/types.h>
+#include <linux/mutex.h>
+#include <linux/device.h>
+#include <linux/spi/spi.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <linux/module.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+/*
+ * Although chip's max frequency is 2Mhz, it needs 600ns between CS and the
+ * first falling edge of SCLK, so frequency should be at most 1 / (2 * 6e-7)
+ */
+#define AD2S90_MAX_SPI_FREQ_HZ  830000
+
+struct ad2s90_state {
+	struct mutex lock; /* lock to protect rx buffer */
+	struct spi_device *sdev;
+	u8 rx[2] __aligned(IIO_DMA_MINALIGN);
+};
+
+static int ad2s90_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val,
+			   int *val2,
+			   long m)
+{
+	int ret;
+	struct ad2s90_state *st = iio_priv(indio_dev);
+
+	if (chan->type != IIO_ANGL)
+		return -EINVAL;
+
+	switch (m) {
+	case IIO_CHAN_INFO_SCALE:
+		/* 2 * Pi / 2^12 */
+		*val = 6283; /* mV */
+		*val2 = 12;
+		return IIO_VAL_FRACTIONAL_LOG2;
+	case IIO_CHAN_INFO_RAW:
+		mutex_lock(&st->lock);
+		ret = spi_read(st->sdev, st->rx, 2);
+		if (ret < 0) {
+			mutex_unlock(&st->lock);
+			return ret;
+		}
+		*val = (((u16)(st->rx[0])) << 4) | ((st->rx[1] & 0xF0) >> 4);
+
+		mutex_unlock(&st->lock);
+
+		return IIO_VAL_INT;
+	default:
+		break;
+	}
+
+	return -EINVAL;
+}
+
+static const struct iio_info ad2s90_info = {
+	.read_raw = ad2s90_read_raw,
+};
+
+static const struct iio_chan_spec ad2s90_chan = {
+	.type = IIO_ANGL,
+	.indexed = 1,
+	.channel = 0,
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
+};
+
+static int ad2s90_probe(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev;
+	struct ad2s90_state *st;
+
+	if (spi->max_speed_hz > AD2S90_MAX_SPI_FREQ_HZ) {
+		dev_err(&spi->dev, "SPI CLK, %d Hz exceeds %d Hz\n",
+			spi->max_speed_hz, AD2S90_MAX_SPI_FREQ_HZ);
+		return -EINVAL;
+	}
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+	st = iio_priv(indio_dev);
+	spi_set_drvdata(spi, indio_dev);
+
+	mutex_init(&st->lock);
+	st->sdev = spi;
+	indio_dev->info = &ad2s90_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = &ad2s90_chan;
+	indio_dev->num_channels = 1;
+	indio_dev->name = spi_get_device_id(spi)->name;
+
+	return devm_iio_device_register(indio_dev->dev.parent, indio_dev);
+}
+
+static const struct of_device_id ad2s90_of_match[] = {
+	{ .compatible = "adi,ad2s90", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ad2s90_of_match);
+
+static const struct spi_device_id ad2s90_id[] = {
+	{ .name = "ad2s90" },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, ad2s90_id);
+
+static struct spi_driver ad2s90_driver = {
+	.driver = {
+		.name = "ad2s90",
+		.of_match_table = ad2s90_of_match,
+	},
+	.probe = ad2s90_probe,
+	.id_table = ad2s90_id,
+};
+module_spi_driver(ad2s90_driver);
+
+MODULE_AUTHOR("Graff Yang <graff.yang@gmail.com>");
+MODULE_DESCRIPTION("Analog Devices AD2S90 Resolver to Digital SPI driver");
+MODULE_LICENSE("GPL v2");