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, 147 insertions, 0 deletions

diff --git a/drivers/hid/hid-lg3ff.c b/drivers/hid/hid-lg3ff.c
new file mode 100644
index 000000000..109735b89
--- /dev/null
+++ b/drivers/hid/hid-lg3ff.c
@@ -0,0 +1,147 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Force feedback support for Logitech Flight System G940
+ *
+ *  Copyright (c) 2009 Gary Stein <LordCnidarian@gmail.com>
+ */
+
+/*
+ */
+
+
+#include <linux/input.h>
+#include <linux/hid.h>
+
+#include "hid-lg.h"
+
+/*
+ * G940 Theory of Operation (from experimentation)
+ *
+ * There are 63 fields (only 3 of them currently used)
+ * 0 - seems to be command field
+ * 1 - 30 deal with the x axis
+ * 31 -60 deal with the y axis
+ *
+ * Field 1 is x axis constant force
+ * Field 31 is y axis constant force
+ *
+ * other interesting fields 1,2,3,4 on x axis
+ * (same for 31,32,33,34 on y axis)
+ *
+ * 0 0 127 127 makes the joystick autocenter hard
+ *
+ * 127 0 127 127 makes the joystick loose on the right,
+ * but stops all movemnt left
+ *
+ * -127 0 -127 -127 makes the joystick loose on the left,
+ * but stops all movement right
+ *
+ * 0 0 -127 -127 makes the joystick rattle very hard
+ *
+ * I'm sure these are effects that I don't know enough about them
+ */
+
+static int hid_lg3ff_play(struct input_dev *dev, void *data,
+			 struct ff_effect *effect)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct list_head *report_list = &hid->report_enum[HID_OUTPUT_REPORT].report_list;
+	struct hid_report *report = list_entry(report_list->next, struct hid_report, list);
+	int x, y;
+
+/*
+ * Available values in the field should always be 63, but we only use up to
+ * 35. Instead, clear the entire area, however big it is.
+ */
+	memset(report->field[0]->value, 0,
+	       sizeof(__s32) * report->field[0]->report_count);
+
+	switch (effect->type) {
+	case FF_CONSTANT:
+/*
+ * Already clamped in ff_memless
+ * 0 is center (different then other logitech)
+ */
+		x = effect->u.ramp.start_level;
+		y = effect->u.ramp.end_level;
+
+		/* send command byte */
+		report->field[0]->value[0] = 0x51;
+
+/*
+ * Sign backwards from other Force3d pro
+ * which get recast here in two's complement 8 bits
+ */
+		report->field[0]->value[1] = (unsigned char)(-x);
+		report->field[0]->value[31] = (unsigned char)(-y);
+
+		hid_hw_request(hid, report, HID_REQ_SET_REPORT);
+		break;
+	}
+	return 0;
+}
+static void hid_lg3ff_set_autocenter(struct input_dev *dev, u16 magnitude)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct list_head *report_list = &hid->report_enum[HID_OUTPUT_REPORT].report_list;
+	struct hid_report *report = list_entry(report_list->next, struct hid_report, list);
+
+/*
+ * Auto Centering probed from device
+ * NOTE: deadman's switch on G940 must be covered
+ * for effects to work
+ */
+	report->field[0]->value[0] = 0x51;
+	report->field[0]->value[1] = 0x00;
+	report->field[0]->value[2] = 0x00;
+	report->field[0]->value[3] = 0x7F;
+	report->field[0]->value[4] = 0x7F;
+	report->field[0]->value[31] = 0x00;
+	report->field[0]->value[32] = 0x00;
+	report->field[0]->value[33] = 0x7F;
+	report->field[0]->value[34] = 0x7F;
+
+	hid_hw_request(hid, report, HID_REQ_SET_REPORT);
+}
+
+
+static const signed short ff3_joystick_ac[] = {
+	FF_CONSTANT,
+	FF_AUTOCENTER,
+	-1
+};
+
+int lg3ff_init(struct hid_device *hid)
+{
+	struct hid_input *hidinput;
+	struct input_dev *dev;
+	const signed short *ff_bits = ff3_joystick_ac;
+	int error;
+	int i;
+
+	if (list_empty(&hid->inputs)) {
+		hid_err(hid, "no inputs found\n");
+		return -ENODEV;
+	}
+	hidinput = list_entry(hid->inputs.next, struct hid_input, list);
+	dev = hidinput->input;
+
+	/* Check that the report looks ok */
+	if (!hid_validate_values(hid, HID_OUTPUT_REPORT, 0, 0, 35))
+		return -ENODEV;
+
+	/* Assume single fixed device G940 */
+	for (i = 0; ff_bits[i] >= 0; i++)
+		set_bit(ff_bits[i], dev->ffbit);
+
+	error = input_ff_create_memless(dev, NULL, hid_lg3ff_play);
+	if (error)
+		return error;
+
+	if (test_bit(FF_AUTOCENTER, dev->ffbit))
+		dev->ff->set_autocenter = hid_lg3ff_set_autocenter;
+
+	hid_info(hid, "Force feedback for Logitech Flight System G940 by Gary Stein <LordCnidarian@gmail.com>\n");
+	return 0;
+}
+