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, 103 insertions, 0 deletions

diff --git a/drivers/input/misc/ad714x-spi.c b/drivers/input/misc/ad714x-spi.c
new file mode 100644
index 000000000..eb13b4cd6
--- /dev/null
+++ b/drivers/input/misc/ad714x-spi.c
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * AD714X CapTouch Programmable Controller driver (SPI bus)
+ *
+ * Copyright 2009-2011 Analog Devices Inc.
+ */
+
+#include <linux/input.h>	/* BUS_SPI */
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+#include <linux/pm.h>
+#include <linux/types.h>
+#include "ad714x.h"
+
+#define AD714x_SPI_CMD_PREFIX      0xE000   /* bits 15:11 */
+#define AD714x_SPI_READ            BIT(10)
+
+static int ad714x_spi_read(struct ad714x_chip *chip,
+			   unsigned short reg, unsigned short *data, size_t len)
+{
+	struct spi_device *spi = to_spi_device(chip->dev);
+	struct spi_message message;
+	struct spi_transfer xfer[2];
+	int i;
+	int error;
+
+	spi_message_init(&message);
+	memset(xfer, 0, sizeof(xfer));
+
+	chip->xfer_buf[0] = cpu_to_be16(AD714x_SPI_CMD_PREFIX |
+					AD714x_SPI_READ | reg);
+	xfer[0].tx_buf = &chip->xfer_buf[0];
+	xfer[0].len = sizeof(chip->xfer_buf[0]);
+	spi_message_add_tail(&xfer[0], &message);
+
+	xfer[1].rx_buf = &chip->xfer_buf[1];
+	xfer[1].len = sizeof(chip->xfer_buf[1]) * len;
+	spi_message_add_tail(&xfer[1], &message);
+
+	error = spi_sync(spi, &message);
+	if (unlikely(error)) {
+		dev_err(chip->dev, "SPI read error: %d\n", error);
+		return error;
+	}
+
+	for (i = 0; i < len; i++)
+		data[i] = be16_to_cpu(chip->xfer_buf[i + 1]);
+
+	return 0;
+}
+
+static int ad714x_spi_write(struct ad714x_chip *chip,
+			    unsigned short reg, unsigned short data)
+{
+	struct spi_device *spi = to_spi_device(chip->dev);
+	int error;
+
+	chip->xfer_buf[0] = cpu_to_be16(AD714x_SPI_CMD_PREFIX | reg);
+	chip->xfer_buf[1] = cpu_to_be16(data);
+
+	error = spi_write(spi, (u8 *)chip->xfer_buf,
+			  2 * sizeof(*chip->xfer_buf));
+	if (unlikely(error)) {
+		dev_err(chip->dev, "SPI write error: %d\n", error);
+		return error;
+	}
+
+	return 0;
+}
+
+static int ad714x_spi_probe(struct spi_device *spi)
+{
+	struct ad714x_chip *chip;
+	int err;
+
+	spi->bits_per_word = 8;
+	err = spi_setup(spi);
+	if (err < 0)
+		return err;
+
+	chip = ad714x_probe(&spi->dev, BUS_SPI, spi->irq,
+			    ad714x_spi_read, ad714x_spi_write);
+	if (IS_ERR(chip))
+		return PTR_ERR(chip);
+
+	spi_set_drvdata(spi, chip);
+
+	return 0;
+}
+
+static struct spi_driver ad714x_spi_driver = {
+	.driver = {
+		.name	= "ad714x_captouch",
+		.pm	= pm_sleep_ptr(&ad714x_pm),
+	},
+	.probe		= ad714x_spi_probe,
+};
+
+module_spi_driver(ad714x_spi_driver);
+
+MODULE_DESCRIPTION("Analog Devices AD714X Capacitance Touch Sensor SPI Bus Driver");
+MODULE_AUTHOR("Barry Song <21cnbao@gmail.com>");
+MODULE_LICENSE("GPL");