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, 72 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/ad7879-spi.c b/drivers/input/touchscreen/ad7879-spi.c
new file mode 100644
index 000000000..064968fe5
--- /dev/null
+++ b/drivers/input/touchscreen/ad7879-spi.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * AD7879/AD7889 touchscreen (SPI bus)
+ *
+ * Copyright (C) 2008-2010 Michael Hennerich, Analog Devices Inc.
+ */
+
+#include <linux/input.h>	/* BUS_SPI */
+#include <linux/pm.h>
+#include <linux/spi/spi.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+
+#include "ad7879.h"
+
+#define AD7879_DEVID		0x7A	/* AD7879/AD7889 */
+
+#define MAX_SPI_FREQ_HZ      5000000
+
+#define AD7879_CMD_MAGIC     0xE0
+#define AD7879_CMD_READ      BIT(2)
+
+static const struct regmap_config ad7879_spi_regmap_config = {
+	.reg_bits = 16,
+	.val_bits = 16,
+	.max_register = 15,
+	.read_flag_mask = AD7879_CMD_MAGIC | AD7879_CMD_READ,
+	.write_flag_mask = AD7879_CMD_MAGIC,
+};
+
+static int ad7879_spi_probe(struct spi_device *spi)
+{
+	struct regmap *regmap;
+
+	/* don't exceed max specified SPI CLK frequency */
+	if (spi->max_speed_hz > MAX_SPI_FREQ_HZ) {
+		dev_err(&spi->dev, "SPI CLK %d Hz?\n", spi->max_speed_hz);
+		return -EINVAL;
+	}
+
+	regmap = devm_regmap_init_spi(spi, &ad7879_spi_regmap_config);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	return ad7879_probe(&spi->dev, regmap, spi->irq, BUS_SPI, AD7879_DEVID);
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id ad7879_spi_dt_ids[] = {
+	{ .compatible = "adi,ad7879", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ad7879_spi_dt_ids);
+#endif
+
+static struct spi_driver ad7879_spi_driver = {
+	.driver = {
+		.name		= "ad7879",
+		.dev_groups	= ad7879_groups,
+		.pm		= &ad7879_pm_ops,
+		.of_match_table	= of_match_ptr(ad7879_spi_dt_ids),
+	},
+	.probe		= ad7879_spi_probe,
+};
+
+module_spi_driver(ad7879_spi_driver);
+
+MODULE_AUTHOR("Michael Hennerich <michael.hennerich@analog.com>");
+MODULE_DESCRIPTION("AD7879(-1) touchscreen SPI bus driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("spi:ad7879");