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, 133 insertions, 0 deletions

diff --git a/drivers/hid/hid-google-stadiaff.c b/drivers/hid/hid-google-stadiaff.c
new file mode 100644
index 000000000..0214aae6b
--- /dev/null
+++ b/drivers/hid/hid-google-stadiaff.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Stadia controller rumble support.
+ *
+ * Copyright 2023 Google LLC
+ */
+
+#include <linux/hid.h>
+#include <linux/input.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+#define STADIA_FF_REPORT_ID 5
+
+struct stadiaff_device {
+	struct hid_device *hid;
+	struct hid_report *report;
+	u32 magnitudes;
+	struct work_struct work;
+};
+
+static void stadiaff_work(struct work_struct *work)
+{
+	struct stadiaff_device *stadiaff =
+		container_of(work, struct stadiaff_device, work);
+	struct hid_field *rumble_field = stadiaff->report->field[0];
+	u32 mags = READ_ONCE(stadiaff->magnitudes);
+
+	rumble_field->value[0] = mags & 0xffff;
+	rumble_field->value[1] = (mags >> 16) & 0xffff;
+
+	hid_hw_request(stadiaff->hid, stadiaff->report, HID_REQ_SET_REPORT);
+}
+
+static int stadiaff_play(struct input_dev *dev, void *data,
+			 struct ff_effect *effect)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct stadiaff_device *stadiaff = hid_get_drvdata(hid);
+	u32 mags = (u32)effect->u.rumble.strong_magnitude |
+		  ((u32)effect->u.rumble.weak_magnitude << 16);
+
+	WRITE_ONCE(stadiaff->magnitudes, mags);
+	schedule_work(&stadiaff->work);
+
+	return 0;
+}
+
+static int stadia_input_open(struct input_dev *dev)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct stadiaff_device *stadiaff = hid_get_drvdata(hid);
+	int error;
+
+	error = hid_hw_open(hid);
+	if (error)
+		return error;
+
+	enable_work(&stadiaff->work);
+	return 0;
+}
+
+static void stadia_input_close(struct input_dev *dev)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct stadiaff_device *stadiaff = hid_get_drvdata(hid);
+
+	WRITE_ONCE(stadiaff->magnitudes, 0);
+	stadiaff_work(&stadiaff->work);
+	disable_work_sync(&stadiaff->work);
+
+	hid_hw_close(hid);
+}
+
+static int stadia_input_configured(struct hid_device *hid, struct hid_input *hidinput)
+{
+	struct stadiaff_device *stadiaff;
+	struct hid_report *report;
+	struct input_dev *dev = hidinput->input;
+	int error;
+
+	if (!list_is_first(&hidinput->list, &hid->inputs))
+		return 0;
+
+	report = hid_validate_values(hid, HID_OUTPUT_REPORT,
+				     STADIA_FF_REPORT_ID, 0, 2);
+	if (!report)
+		return -ENODEV;
+
+	stadiaff = devm_kzalloc(&hid->dev, sizeof(struct stadiaff_device),
+				GFP_KERNEL);
+	if (!stadiaff)
+		return -ENOMEM;
+
+	hid_set_drvdata(hid, stadiaff);
+
+	input_set_capability(dev, EV_FF, FF_RUMBLE);
+
+	error = input_ff_create_memless(dev, NULL, stadiaff_play);
+	if (error)
+		return error;
+
+	stadiaff->hid = hid;
+	stadiaff->report = report;
+	INIT_WORK(&stadiaff->work, stadiaff_work);
+	disable_work_sync(&stadiaff->work);
+
+	dev->open = stadia_input_open;
+	dev->close = stadia_input_close;
+
+	hid_info(hid, "Force Feedback for Google Stadia controller\n");
+
+	return 0;
+}
+
+static const struct hid_device_id stadia_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_GOOGLE, USB_DEVICE_ID_GOOGLE_STADIA) },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_GOOGLE, USB_DEVICE_ID_GOOGLE_STADIA) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, stadia_devices);
+
+static struct hid_driver stadia_driver = {
+	.name = "stadia",
+	.id_table = stadia_devices,
+	.input_configured = stadia_input_configured,
+};
+module_hid_driver(stadia_driver);
+
+MODULE_DESCRIPTION("Google Stadia controller rumble support.");
+MODULE_LICENSE("GPL");