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, 115 insertions, 0 deletions

diff --git a/drivers/hid/hid-zpff.c b/drivers/hid/hid-zpff.c
new file mode 100644
index 000000000..b565c59d3
--- /dev/null
+++ b/drivers/hid/hid-zpff.c
@@ -0,0 +1,115 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Force feedback support for Zeroplus based devices
+ *
+ *  Copyright (c) 2005, 2006 Anssi Hannula <anssi.hannula@gmail.com>
+ */
+
+/*
+ */
+
+
+#include <linux/hid.h>
+#include <linux/input.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+#ifdef CONFIG_ZEROPLUS_FF
+
+struct zpff_device {
+	struct hid_report *report;
+};
+
+static int zpff_play(struct input_dev *dev, void *data,
+			 struct ff_effect *effect)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct zpff_device *zpff = data;
+	int left, right;
+
+	/*
+	 * The following is specified the other way around in the Zeroplus
+	 * datasheet but the order below is correct for the XFX Executioner;
+	 * however it is possible that the XFX Executioner is an exception
+	 */
+
+	left = effect->u.rumble.strong_magnitude;
+	right = effect->u.rumble.weak_magnitude;
+	dbg_hid("called with 0x%04x 0x%04x\n", left, right);
+
+	left = left * 0x7f / 0xffff;
+	right = right * 0x7f / 0xffff;
+
+	zpff->report->field[2]->value[0] = left;
+	zpff->report->field[3]->value[0] = right;
+	dbg_hid("running with 0x%02x 0x%02x\n", left, right);
+	hid_hw_request(hid, zpff->report, HID_REQ_SET_REPORT);
+
+	return 0;
+}
+
+static int zp_input_configured(struct hid_device *hid, struct hid_input *hidinput)
+{
+	struct zpff_device *zpff;
+	struct hid_report *report;
+	struct input_dev *dev = hidinput->input;
+	int i, error;
+
+	if (!list_is_first(&hidinput->list, &hid->inputs))
+		return 0;
+
+	for (i = 0; i < 4; i++) {
+		report = hid_validate_values(hid, HID_OUTPUT_REPORT, 0, i, 1);
+		if (!report)
+			return -ENODEV;
+	}
+
+	zpff = kzalloc_obj(struct zpff_device);
+	if (!zpff)
+		return -ENOMEM;
+
+	zpff->report = report;
+	set_bit(FF_RUMBLE, dev->ffbit);
+
+	error = input_ff_create_memless(dev, zpff, zpff_play);
+	if (error) {
+		kfree(zpff);
+		return error;
+	}
+
+	zpff->report->field[0]->value[0] = 0x00;
+	zpff->report->field[1]->value[0] = 0x02;
+	zpff->report->field[2]->value[0] = 0x00;
+	zpff->report->field[3]->value[0] = 0x00;
+	hid_hw_request(hid, zpff->report, HID_REQ_SET_REPORT);
+
+	hid_info(hid, "force feedback for Zeroplus based devices by Anssi Hannula <anssi.hannula@gmail.com>\n");
+
+	return 0;
+}
+#else
+static inline int zp_input_configured(struct hid_device *hid,
+				      struct hid_input *hidinput)
+{
+	return 0;
+}
+#endif
+
+static const struct hid_device_id zp_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ZEROPLUS, 0x0005) },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ZEROPLUS, 0x0030) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, zp_devices);
+
+static struct hid_driver zp_driver = {
+	.name = "zeroplus",
+	.id_table = zp_devices,
+	.input_configured = zp_input_configured,
+};
+module_hid_driver(zp_driver);
+
+MODULE_DESCRIPTION("Force feedback support for Zeroplus based devices");
+MODULE_LICENSE("GPL");