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, 117 insertions, 0 deletions

diff --git a/drivers/hid/hid-hyperx.c b/drivers/hid/hid-hyperx.c
new file mode 100644
index 000000000..18d2dc24c
--- /dev/null
+++ b/drivers/hid/hid-hyperx.c
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  HID driver for the HyperX QuadCast 2 microphone
+ *
+ *  The tap-to-mute button is handled entirely in the device firmware: it gates
+ *  the audio internally and does not send the Telephony "Phone Mute" usage its
+ *  own report descriptor advertises.  The resulting mute state is only reported
+ *  through a vendor-defined collection, which hid-input cannot map, so the
+ *  button is invisible to userspace.
+ *
+ *  Copyright (c) 2026 Benjamin Blume <benjaminblume@posteo.de>
+ */
+
+#include <linux/hid.h>
+#include <linux/input.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+#define HYPERX_QC2_REPORT_ID	0x77
+#define HYPERX_QC2_EVENT_MUTE	0x06
+#define HYPERX_QC2_MUTE_LEN	3
+
+struct hyperx_drvdata {
+	struct input_dev *input;
+	bool muted;
+	bool have_state;
+};
+
+static int hyperx_input_configured(struct hid_device *hdev,
+				   struct hid_input *hi)
+{
+	struct hyperx_drvdata *drvdata = hid_get_drvdata(hdev);
+
+	/*
+	 * The device exposes several application collections.  Prefer the
+	 * telephony one, which already advertises KEY_MICMUTE, and fall back
+	 * to the first collection otherwise.
+	 */
+	if (!drvdata->input || test_bit(KEY_MICMUTE, hi->input->keybit)) {
+		drvdata->input = hi->input;
+		input_set_capability(drvdata->input, EV_KEY, KEY_MICMUTE);
+	}
+
+	return 0;
+}
+
+static int hyperx_raw_event(struct hid_device *hdev, struct hid_report *report,
+			    u8 *data, int size)
+{
+	struct hyperx_drvdata *drvdata = hid_get_drvdata(hdev);
+	bool muted;
+
+	if (!(hdev->claimed & HID_CLAIMED_INPUT) || !drvdata->input)
+		return 0;
+
+	if (size < HYPERX_QC2_MUTE_LEN || data[0] != HYPERX_QC2_REPORT_ID ||
+	    data[1] != HYPERX_QC2_EVENT_MUTE)
+		return 0;
+
+	muted = data[2];
+	if (drvdata->have_state && muted == drvdata->muted)
+		return 0;
+
+	drvdata->muted = muted;
+	drvdata->have_state = true;
+
+	/*
+	 * The device reports the resulting absolute state, while KEY_MICMUTE is
+	 * a momentary key that userspace acts on as a toggle.  Emit one
+	 * keypress per state change.
+	 */
+	input_report_key(drvdata->input, KEY_MICMUTE, 1);
+	input_sync(drvdata->input);
+	input_report_key(drvdata->input, KEY_MICMUTE, 0);
+	input_sync(drvdata->input);
+
+	return 0;
+}
+
+static int hyperx_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	struct hyperx_drvdata *drvdata;
+	int ret;
+
+	drvdata = devm_kzalloc(&hdev->dev, sizeof(*drvdata), GFP_KERNEL);
+	if (!drvdata)
+		return -ENOMEM;
+
+	hid_set_drvdata(hdev, drvdata);
+
+	ret = hid_parse(hdev);
+	if (ret)
+		return ret;
+
+	return hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+}
+
+static const struct hid_device_id hyperx_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_HP,
+			 USB_PRODUCT_ID_HP_HYPERX_QUADCAST_2) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, hyperx_devices);
+
+static struct hid_driver hyperx_driver = {
+	.name			= "hyperx",
+	.id_table		= hyperx_devices,
+	.probe			= hyperx_probe,
+	.input_configured	= hyperx_input_configured,
+	.raw_event		= hyperx_raw_event,
+};
+module_hid_driver(hyperx_driver);
+
+MODULE_DESCRIPTION("HID driver for the HyperX QuadCast 2 microphone");
+MODULE_AUTHOR("Benjamin Blume <benjaminblume@posteo.de>");
+MODULE_LICENSE("GPL");