From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops 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 --- drivers/leds/trigger/ledtrig-backlight.c | 140 +++++++++++++++++++++++++++++++ 1 file changed, 140 insertions(+) create mode 100644 drivers/leds/trigger/ledtrig-backlight.c (limited to 'drivers/leds/trigger/ledtrig-backlight.c') diff --git a/drivers/leds/trigger/ledtrig-backlight.c b/drivers/leds/trigger/ledtrig-backlight.c new file mode 100644 index 000000000..e67bc7c2a --- /dev/null +++ b/drivers/leds/trigger/ledtrig-backlight.c @@ -0,0 +1,140 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Backlight emulation LED trigger + * + * Copyright 2008 (C) Rodolfo Giometti + * Copyright 2008 (C) Eurotech S.p.A. + */ + +#include +#include +#include +#include +#include +#include "../leds.h" + +#define BLANK 1 +#define UNBLANK 0 + +struct bl_trig_notifier { + struct led_classdev *led; + int brightness; + int old_status; + unsigned invert; + + struct list_head entry; +}; + +static DEFINE_MUTEX(ledtrig_backlight_list_mutex); +static LIST_HEAD(ledtrig_backlight_list); + +static void ledtrig_backlight_notify_blank(struct bl_trig_notifier *n, int new_status) +{ + struct led_classdev *led = n->led; + + if (new_status == n->old_status) + return; + + if ((n->old_status == UNBLANK) ^ n->invert) { + n->brightness = led->brightness; + led_set_brightness_nosleep(led, LED_OFF); + } else { + led_set_brightness_nosleep(led, n->brightness); + } + + n->old_status = new_status; +} + +void ledtrig_backlight_blank(bool blank) +{ + struct bl_trig_notifier *n; + int new_status = blank ? BLANK : UNBLANK; + + guard(mutex)(&ledtrig_backlight_list_mutex); + + list_for_each_entry(n, &ledtrig_backlight_list, entry) + ledtrig_backlight_notify_blank(n, new_status); +} +EXPORT_SYMBOL(ledtrig_backlight_blank); + +static ssize_t bl_trig_invert_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct bl_trig_notifier *n = led_trigger_get_drvdata(dev); + + return sprintf(buf, "%u\n", n->invert); +} + +static ssize_t bl_trig_invert_store(struct device *dev, + struct device_attribute *attr, const char *buf, size_t num) +{ + struct led_classdev *led = led_trigger_get_led(dev); + struct bl_trig_notifier *n = led_trigger_get_drvdata(dev); + unsigned long invert; + int ret; + + ret = kstrtoul(buf, 10, &invert); + if (ret < 0) + return ret; + + if (invert > 1) + return -EINVAL; + + n->invert = invert; + + /* After inverting, we need to update the LED. */ + if ((n->old_status == BLANK) ^ n->invert) + led_set_brightness_nosleep(led, LED_OFF); + else + led_set_brightness_nosleep(led, n->brightness); + + return num; +} +static DEVICE_ATTR(inverted, 0644, bl_trig_invert_show, bl_trig_invert_store); + +static struct attribute *bl_trig_attrs[] = { + &dev_attr_inverted.attr, + NULL, +}; +ATTRIBUTE_GROUPS(bl_trig); + +static int bl_trig_activate(struct led_classdev *led) +{ + struct bl_trig_notifier *n; + + n = kzalloc_obj(struct bl_trig_notifier); + if (!n) + return -ENOMEM; + led_set_trigger_data(led, n); + + n->led = led; + n->brightness = led->brightness; + n->old_status = UNBLANK; + + guard(mutex)(&ledtrig_backlight_list_mutex); + list_add(&n->entry, &ledtrig_backlight_list); + + return 0; +} + +static void bl_trig_deactivate(struct led_classdev *led) +{ + struct bl_trig_notifier *n = led_get_trigger_data(led); + + guard(mutex)(&ledtrig_backlight_list_mutex); + list_del(&n->entry); + + kfree(n); +} + +static struct led_trigger bl_led_trigger = { + .name = "backlight", + .activate = bl_trig_activate, + .deactivate = bl_trig_deactivate, + .groups = bl_trig_groups, +}; +module_led_trigger(bl_led_trigger); + +MODULE_AUTHOR("Rodolfo Giometti "); +MODULE_DESCRIPTION("Backlight emulation LED trigger"); +MODULE_LICENSE("GPL v2"); -- cgit v1.3.1