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, 103 insertions, 0 deletions

diff --git a/drivers/hid/hid-picolcd_backlight.c b/drivers/hid/hid-picolcd_backlight.c
new file mode 100644
index 000000000..4b43b6453
--- /dev/null
+++ b/drivers/hid/hid-picolcd_backlight.c
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/***************************************************************************
+ *   Copyright (C) 2010-2012 by Bruno Prémont <bonbons@linux-vserver.org>  *
+ *                                                                         *
+ *   Based on Logitech G13 driver (v0.4)                                   *
+ *     Copyright (C) 2009 by Rick L. Vinyard, Jr. <rvinyard@cs.nmsu.edu>   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include <linux/hid.h>
+
+#include <linux/backlight.h>
+
+#include "hid-picolcd.h"
+
+static int picolcd_get_brightness(struct backlight_device *bdev)
+{
+	struct picolcd_data *data = bl_get_data(bdev);
+	return data->lcd_brightness;
+}
+
+static int picolcd_set_brightness(struct backlight_device *bdev)
+{
+	struct picolcd_data *data = bl_get_data(bdev);
+	struct hid_report *report = picolcd_out_report(REPORT_BRIGHTNESS, data->hdev);
+	unsigned long flags;
+
+	if (!report || report->maxfield != 1 || report->field[0]->report_count != 1)
+		return -ENODEV;
+
+	data->lcd_brightness = bdev->props.brightness & 0x0ff;
+	data->lcd_power      = bdev->props.power;
+	spin_lock_irqsave(&data->lock, flags);
+	hid_set_field(report->field[0], 0,
+		      data->lcd_power == BACKLIGHT_POWER_ON ? data->lcd_brightness : 0);
+	if (!(data->status & PICOLCD_FAILED))
+		hid_hw_request(data->hdev, report, HID_REQ_SET_REPORT);
+	spin_unlock_irqrestore(&data->lock, flags);
+	return 0;
+}
+
+static const struct backlight_ops picolcd_blops = {
+	.update_status  = picolcd_set_brightness,
+	.get_brightness = picolcd_get_brightness,
+};
+
+int picolcd_init_backlight(struct picolcd_data *data, struct hid_report *report)
+{
+	struct device *dev = &data->hdev->dev;
+	struct backlight_device *bdev;
+	struct backlight_properties props;
+	if (!report)
+		return -ENODEV;
+	if (report->maxfield != 1 || report->field[0]->report_count != 1 ||
+			report->field[0]->report_size != 8) {
+		dev_err(dev, "unsupported BRIGHTNESS report");
+		return -EINVAL;
+	}
+
+	memset(&props, 0, sizeof(props));
+	props.type = BACKLIGHT_RAW;
+	props.max_brightness = 0xff;
+	bdev = backlight_device_register(dev_name(dev), dev, data,
+			&picolcd_blops, &props);
+	if (IS_ERR(bdev)) {
+		dev_err(dev, "failed to register backlight\n");
+		return PTR_ERR(bdev);
+	}
+	bdev->props.brightness     = 0xff;
+	data->lcd_brightness       = 0xff;
+	data->backlight            = bdev;
+	picolcd_set_brightness(bdev);
+	return 0;
+}
+
+void picolcd_exit_backlight(struct picolcd_data *data)
+{
+	struct backlight_device *bdev = data->backlight;
+
+	data->backlight = NULL;
+	backlight_device_unregister(bdev);
+}
+
+int picolcd_resume_backlight(struct picolcd_data *data)
+{
+	if (!data->backlight)
+		return 0;
+	return picolcd_set_brightness(data->backlight);
+}
+
+#ifdef CONFIG_PM
+void picolcd_suspend_backlight(struct picolcd_data *data)
+{
+	int bl_power = data->lcd_power;
+	if (!data->backlight)
+		return;
+
+	data->backlight->props.power = BACKLIGHT_POWER_OFF;
+	picolcd_set_brightness(data->backlight);
+	data->lcd_power = data->backlight->props.power = bl_power;
+}
+#endif /* CONFIG_PM */
+