leds: trigger: input-events: Rewrite to fix a serious locking issue

The input subsystem registers LEDs with default triggers while holding
the input_lock and input_register_handler() takes the input_lock this
means that a triggers activate method cannot directly call
input_register_handler() as the old ledtrig-input-events code is doing.

The initial implementation of the input-events trigger mainly did not use
the simple LED trigger mechanism because that mechanism had an issue with
the initial state of a newly activated LED not matching the last
led_trigger_event() call for the trigger. This issue has been fixed in
commit 822c91e72eac ("leds: trigger: Store brightness set by
led_trigger_event()").

Rewrite the "input-events" trigger to use the simple LED trigger mechanism,
registering a single input_handler at module_init() time and using
led_trigger_event() to set the brightness for all LEDs controlled by this
trigger.

Compared to the old code this looses the ability for the user to configure
a different brightness for the on state then LED_FULL, this is standard for
simple LED triggers and since this trigger is only in for-leds-next ATM
losing that functionality is not a regression.

This also changes the configurability of the LED off timeout from a per
LED setting to a global setting (runtime modifiable module-parameter).

Switching to registering a single input_handler at module_init() time fixes
the following locking issue reported by lockdep:

[ 2840.220145] usb 1-1.3: new low-speed USB device number 3 using xhci_hcd
[ 2840.307172] usb 1-1.3: New USB device found, idVendor=0603, idProduct=0002, bcdDevice= 2.21
[ 2840.307375] usb 1-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[ 2840.307423] usb 1-1.3: Product: USB Composite Device
[ 2840.307456] usb 1-1.3: Manufacturer: SINO WEALTH
[ 2840.333985] input: SINO WEALTH USB Composite Device as /devices/pci0000:00/0000:00:14.0/usb1/1-1/1-1.3/1-1.3:1.0/0003:0603:0002.0007/input/input19

[ 2840.386545] ======================================================
[ 2840.386549] WARNING: possible circular locking dependency detected
[ 2840.386554] 6.10.0-rc1+ #97 Tainted: G C E
[ 2840.386558] ------------------------------------------------------
[ 2840.386562] kworker/1:1/52 is trying to acquire lock:
[ 2840.386566] ffff98fcf1629300 (&led_cdev->led_access){+.+.}-{3:3}, at: led_classdev_register_ext+0x1c6/0x380
[ 2840.386590]
but task is already holding lock:
[ 2840.386593] ffffffff88130cc8 (input_mutex){+.+.}-{3:3}, at: input_register_device.cold+0x47/0x150
[ 2840.386608]
which lock already depends on the new lock.

[ 2840.386611]
the existing dependency chain (in reverse order) is:
[ 2840.386615]
-> #3 (input_mutex){+.+.}-{3:3}:
[ 2840.386624] __mutex_lock+0x8c/0xc10
[ 2840.386634] input_register_handler+0x1c/0xf0
[ 2840.386641] 0xffffffffc142c437
[ 2840.386655] led_trigger_set+0x1e1/0x2e0
[ 2840.386661] led_trigger_register+0x170/0x1b0
[ 2840.386666] do_one_initcall+0x5e/0x3a0
[ 2840.386675] do_init_module+0x60/0x220
[ 2840.386683] __do_sys_init_module+0x15f/0x190
[ 2840.386689] do_syscall_64+0x93/0x180
[ 2840.386696] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 2840.386705]
-> #2 (&led_cdev->trigger_lock){+.+.}-{3:3}:
[ 2840.386714] down_write+0x3b/0xd0
[ 2840.386720] led_trigger_register+0x12c/0x1b0
[ 2840.386725] rfkill_register+0xec/0x340 [rfkill]
[ 2840.386739] wiphy_register+0x82a/0x930 [cfg80211]
[ 2840.386907] brcmf_cfg80211_attach+0xcbd/0x1430 [brcmfmac]
[ 2840.386952] brcmf_attach+0x1ba/0x4c0 [brcmfmac]
[ 2840.386991] brcmf_pcie_setup+0x899/0xc70 [brcmfmac]
[ 2840.387030] brcmf_fw_request_done+0x13b/0x180 [brcmfmac]
[ 2840.387070] request_firmware_work_func+0x3b/0x70
[ 2840.387078] process_one_work+0x21a/0x590
[ 2840.387085] worker_thread+0x1d1/0x3e0
[ 2840.387090] kthread+0xee/0x120
[ 2840.387096] ret_from_fork+0x30/0x50
[ 2840.387105] ret_from_fork_asm+0x1a/0x30
[ 2840.387112]
-> #1 (leds_list_lock){++++}-{3:3}:
[ 2840.387123] down_write+0x3b/0xd0
[ 2840.387129] led_classdev_register_ext+0x29e/0x380
[ 2840.387134] 0xffffffffc0e6b74c
[ 2840.387143] platform_probe+0x40/0xa0
[ 2840.387151] really_probe+0xde/0x340
[ 2840.387157] __driver_probe_device+0x78/0x110
[ 2840.387162] driver_probe_device+0x1f/0xa0
[ 2840.387168] __driver_attach+0xba/0x1c0
[ 2840.387173] bus_for_each_dev+0x6b/0xb0
[ 2840.387180] bus_add_driver+0x111/0x1f0
[ 2840.387185] driver_register+0x6e/0xc0
[ 2840.387191] do_one_initcall+0x5e/0x3a0
[ 2840.387197] do_init_module+0x60/0x220
[ 2840.387204] __do_sys_init_module+0x15f/0x190
[ 2840.387210] do_syscall_64+0x93/0x180
[ 2840.387217] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 2840.387224]
-> #0 (&led_cdev->led_access){+.+.}-{3:3}:
[ 2840.387233] __lock_acquire+0x11c6/0x1f20
[ 2840.387239] lock_acquire+0xc8/0x2b0
[ 2840.387244] __mutex_lock+0x8c/0xc10
[ 2840.387251] led_classdev_register_ext+0x1c6/0x380
[ 2840.387256] input_leds_connect+0x139/0x260
[ 2840.387262] input_attach_handler.isra.0+0x75/0x90
[ 2840.387268] input_register_device.cold+0xa1/0x150
[ 2840.387274] hidinput_connect+0x848/0xb00
[ 2840.387280] hid_connect+0x567/0x5a0
[ 2840.387288] hid_hw_start+0x3f/0x60
[ 2840.387294] hid_device_probe+0x10d/0x190
[ 2840.387298] really_probe+0xde/0x340
[ 2840.387304] __driver_probe_device+0x78/0x110
[ 2840.387309] driver_probe_device+0x1f/0xa0
[ 2840.387314] __device_attach_driver+0x85/0x110
[ 2840.387320] bus_for_each_drv+0x78/0xc0
[ 2840.387326] __device_attach+0xb0/0x1b0
[ 2840.387332] bus_probe_device+0x94/0xb0
[ 2840.387337] device_add+0x64a/0x860
[ 2840.387343] hid_add_device+0xe5/0x240
[ 2840.387349] usbhid_probe+0x4bb/0x600
[ 2840.387356] usb_probe_interface+0xea/0x2b0
[ 2840.387363] really_probe+0xde/0x340
[ 2840.387368] __driver_probe_device+0x78/0x110
[ 2840.387373] driver_probe_device+0x1f/0xa0
[ 2840.387378] __device_attach_driver+0x85/0x110
[ 2840.387383] bus_for_each_drv+0x78/0xc0
[ 2840.387390] __device_attach+0xb0/0x1b0
[ 2840.387395] bus_probe_device+0x94/0xb0
[ 2840.387400] device_add+0x64a/0x860
[ 2840.387405] usb_set_configuration+0x5e8/0x880
[ 2840.387411] usb_generic_driver_probe+0x3e/0x60
[ 2840.387418] usb_probe_device+0x3d/0x120
[ 2840.387423] really_probe+0xde/0x340
[ 2840.387428] __driver_probe_device+0x78/0x110
[ 2840.387434] driver_probe_device+0x1f/0xa0
[ 2840.387439] __device_attach_driver+0x85/0x110
[ 2840.387444] bus_for_each_drv+0x78/0xc0
[ 2840.387451] __device_attach+0xb0/0x1b0
[ 2840.387456] bus_probe_device+0x94/0xb0
[ 2840.387461] device_add+0x64a/0x860
[ 2840.387466] usb_new_device.cold+0x141/0x38f
[ 2840.387473] hub_event+0x1166/0x1980
[ 2840.387479] process_one_work+0x21a/0x590
[ 2840.387484] worker_thread+0x1d1/0x3e0
[ 2840.387488] kthread+0xee/0x120
[ 2840.387493] ret_from_fork+0x30/0x50
[ 2840.387500] ret_from_fork_asm+0x1a/0x30
[ 2840.387506]
other info that might help us debug this:

[ 2840.387509] Chain exists of:
&led_cdev->led_access --> &led_cdev->trigger_lock --> input_mutex

[ 2840.387520] Possible unsafe locking scenario:

[ 2840.387523] CPU0 CPU1
[ 2840.387526] ---- ----
[ 2840.387529] lock(input_mutex);
[ 2840.387534] lock(&led_cdev->trigger_lock);
[ 2840.387540] lock(input_mutex);
[ 2840.387545] lock(&led_cdev->led_access);
[ 2840.387550]
*** DEADLOCK ***

[ 2840.387552] 7 locks held by kworker/1:1/52:
[ 2840.387557] #0: ffff98fcc1d07148 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x4af/0x590
[ 2840.387570] #1: ffffb67e00213e60 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x1d5/0x590
[ 2840.387583] #2: ffff98fcc6582190 (&dev->mutex){....}-{3:3}, at: hub_event+0x57/0x1980
[ 2840.387596] #3: ffff98fccb3c6990 (&dev->mutex){....}-{3:3}, at: __device_attach+0x26/0x1b0
[ 2840.387610] #4: ffff98fcc5260960 (&dev->mutex){....}-{3:3}, at: __device_attach+0x26/0x1b0
[ 2840.387622] #5: ffff98fce3999a20 (&dev->mutex){....}-{3:3}, at: __device_attach+0x26/0x1b0
[ 2840.387635] #6: ffffffff88130cc8 (input_mutex){+.+.}-{3:3}, at: input_register_device.cold+0x47/0x150
[ 2840.387649]
stack backtrace:
[ 2840.387653] CPU: 1 PID: 52 Comm: kworker/1:1 Tainted: G C E 6.10.0-rc1+ #97
[ 2840.387659] Hardware name: Xiaomi Inc Mipad2/Mipad, BIOS MIPad-P4.X64.0043.R03.1603071414 03/07/2016
[ 2840.387665] Workqueue: usb_hub_wq hub_event
[ 2840.387674] Call Trace:
[ 2840.387681] <TASK>
[ 2840.387689] dump_stack_lvl+0x68/0x90
[ 2840.387700] check_noncircular+0x10d/0x120
[ 2840.387710] ? register_lock_class+0x38/0x480
[ 2840.387717] ? check_noncircular+0x74/0x120
[ 2840.387727] __lock_acquire+0x11c6/0x1f20
[ 2840.387736] lock_acquire+0xc8/0x2b0
[ 2840.387743] ? led_classdev_register_ext+0x1c6/0x380
[ 2840.387753] __mutex_lock+0x8c/0xc10
[ 2840.387760] ? led_classdev_register_ext+0x1c6/0x380
[ 2840.387766] ? _raw_spin_unlock_irqrestore+0x35/0x60
[ 2840.387773] ? klist_next+0x158/0x160
[ 2840.387781] ? led_classdev_register_ext+0x1c6/0x380
[ 2840.387787] ? lockdep_init_map_type+0x58/0x250
[ 2840.387796] ? led_classdev_register_ext+0x1c6/0x380
[ 2840.387802] led_classdev_register_ext+0x1c6/0x380
[ 2840.387810] ? kvasprintf+0x70/0xb0
[ 2840.387820] ? kasprintf+0x3e/0x50
[ 2840.387829] input_leds_connect+0x139/0x260
[ 2840.387838] input_attach_handler.isra.0+0x75/0x90
[ 2840.387846] input_register_device.cold+0xa1/0x150
[ 2840.387854] hidinput_connect+0x848/0xb00
[ 2840.387862] ? usbhid_start+0x45b/0x7b0
[ 2840.387870] hid_connect+0x567/0x5a0
[ 2840.387878] ? __mutex_unlock_slowpath+0x2d/0x260
[ 2840.387891] hid_hw_start+0x3f/0x60
[ 2840.387899] hid_device_probe+0x10d/0x190
[ 2840.387906] ? __pfx___device_attach_driver+0x10/0x10
[ 2840.387913] really_probe+0xde/0x340
[ 2840.387919] ? pm_runtime_barrier+0x50/0x90
[ 2840.387927] __driver_probe_device+0x78/0x110
[ 2840.387934] driver_probe_device+0x1f/0xa0
[ 2840.387941] __device_attach_driver+0x85/0x110
[ 2840.387949] bus_for_each_drv+0x78/0xc0
[ 2840.387959] __device_attach+0xb0/0x1b0
[ 2840.387967] bus_probe_device+0x94/0xb0
[ 2840.387974] device_add+0x64a/0x860
[ 2840.387982] ? __debugfs_create_file+0x14a/0x1c0
[ 2840.387993] hid_add_device+0xe5/0x240
[ 2840.388002] usbhid_probe+0x4bb/0x600
[ 2840.388013] usb_probe_interface+0xea/0x2b0
[ 2840.388021] ? __pfx___device_attach_driver+0x10/0x10
[ 2840.388028] really_probe+0xde/0x340
[ 2840.388034] ? pm_runtime_barrier+0x50/0x90
[ 2840.388040] __driver_probe_device+0x78/0x110
[ 2840.388048] driver_probe_device+0x1f/0xa0
[ 2840.388055] __device_attach_driver+0x85/0x110
[ 2840.388062] bus_for_each_drv+0x78/0xc0
[ 2840.388071] __device_attach+0xb0/0x1b0
[ 2840.388079] bus_probe_device+0x94/0xb0
[ 2840.388086] device_add+0x64a/0x860
[ 2840.388094] ? __mutex_unlock_slowpath+0x2d/0x260
[ 2840.388103] usb_set_configuration+0x5e8/0x880
[ 2840.388114] ? __pfx___device_attach_driver+0x10/0x10
[ 2840.388121] usb_generic_driver_probe+0x3e/0x60
[ 2840.388129] usb_probe_device+0x3d/0x120
[ 2840.388137] really_probe+0xde/0x340
[ 2840.388142] ? pm_runtime_barrier+0x50/0x90
[ 2840.388149] __driver_probe_device+0x78/0x110
[ 2840.388156] driver_probe_device+0x1f/0xa0
[ 2840.388163] __device_attach_driver+0x85/0x110
[ 2840.388171] bus_for_each_drv+0x78/0xc0
[ 2840.388180] __device_attach+0xb0/0x1b0
[ 2840.388188] bus_probe_device+0x94/0xb0
[ 2840.388195] device_add+0x64a/0x860
[ 2840.388202] ? lockdep_hardirqs_on+0x78/0x100
[ 2840.388210] ? _raw_spin_unlock_irqrestore+0x35/0x60
[ 2840.388219] usb_new_device.cold+0x141/0x38f
[ 2840.388227] hub_event+0x1166/0x1980
[ 2840.388242] process_one_work+0x21a/0x590
[ 2840.388249] ? move_linked_works+0x70/0xa0
[ 2840.388260] worker_thread+0x1d1/0x3e0
[ 2840.388268] ? __pfx_worker_thread+0x10/0x10
[ 2840.388273] kthread+0xee/0x120
[ 2840.388279] ? __pfx_kthread+0x10/0x10
[ 2840.388287] ret_from_fork+0x30/0x50
[ 2840.388294] ? __pfx_kthread+0x10/0x10
[ 2840.388301] ret_from_fork_asm+0x1a/0x30
[ 2840.388315] </TASK>
[ 2840.415630] hid-generic 0003:0603:0002.0007: input,hidraw6: USB HID v1.10 Keyboard [SINO WEALTH USB Composite Device] on usb-0000:00:14.0-1.3/input0

Signed-off-by: Hans de Goede <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Lee Jones <[e-mail]>

drivers/leds/trigger/ledtrig-input-events.c

···
  * Input Events LED trigger
  *
  * Copyright (C) 2024 Hans de Goede <[e-mail]>
- * Partially based on Atsushi Nemoto's ledtrig-heartbeat.c.
  */
 
 #include <linux/input.h>
 #include <linux/jiffies.h>
 #include <linux/leds.h>
 #include <linux/module.h>
+#include <linux/moduleparam.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/workqueue.h>
 #include "../leds.h"
 
-#define DEFAULT_LED_OFF_DELAY_MS			5000
+static unsigned long led_off_delay_ms = 5000;
+module_param(led_off_delay_ms, ulong, 0644);
+MODULE_PARM_DESC(led_off_delay_ms,
+	"Specify delay in ms for turning LEDs off after last input event");
 
-struct input_events_data {
-	struct input_handler handler;
+static struct input_events_data {
 	struct delayed_work work;
 	spinlock_t lock;
-	struct led_classdev *led_cdev;
-	int led_cdev_saved_flags;
 	/* To avoid repeatedly setting the brightness while there are events */
 	bool led_on;
 	unsigned long led_off_time;
-	unsigned long led_off_delay;
-};
+} input_events_data;
+
+static struct led_trigger *input_events_led_trigger;
 
 static void led_input_events_work(struct work_struct *work)
 {
···
 	 * running before a new event pushed led_off_time back.
 	 */
 	if (time_after_eq(jiffies, data->led_off_time)) {
-		led_set_brightness_nosleep(data->led_cdev, LED_OFF);
+		led_trigger_event(input_events_led_trigger, LED_OFF);
 		data->led_on = false;
 	}
 
 	spin_unlock_irq(&data->lock);
 }
 
-static ssize_t delay_show(struct device *dev, struct device_attribute *attr, char *buf)
-{
-	struct input_events_data *input_events_data = led_trigger_get_drvdata(dev);
-
-	return sysfs_emit(buf, "%lu\n", input_events_data->led_off_delay);
-}
-
-static ssize_t delay_store(struct device *dev, struct device_attribute *attr,
-			   const char *buf, size_t size)
-{
-	struct input_events_data *input_events_data = led_trigger_get_drvdata(dev);
-	unsigned long delay;
-	int ret;
-
-	ret = kstrtoul(buf, 0, &delay);
-	if (ret)
-		return ret;
-
-	/* Clamp between 0.5 and 1000 seconds */
-	delay = clamp_val(delay, 500UL, 1000000UL);
-	input_events_data->led_off_delay = msecs_to_jiffies(delay);
-
-	return size;
-}
-
-static DEVICE_ATTR_RW(delay);
-
-static struct attribute *input_events_led_attrs[] = {
-	&dev_attr_delay.attr,
-	NULL
-};
-ATTRIBUTE_GROUPS(input_events_led);
-
 static void input_events_event(struct input_handle *handle, unsigned int type,
 			       unsigned int code, int val)
 {
-	struct input_events_data *data =
-		container_of(handle->handler, struct input_events_data, handler);
-	unsigned long led_off_delay = READ_ONCE(data->led_off_delay);
-	struct led_classdev *led_cdev = data->led_cdev;
+	struct input_events_data *data = &input_events_data;
+	unsigned long led_off_delay = msecs_to_jiffies(led_off_delay_ms);
 	unsigned long flags;
-
-	if (test_and_clear_bit(LED_BLINK_BRIGHTNESS_CHANGE, &led_cdev->work_flags))
-		led_cdev->blink_brightness = led_cdev->new_blink_brightness;
 
 	spin_lock_irqsave(&data->lock, flags);
 
 	if (!data->led_on) {
-		led_set_brightness_nosleep(led_cdev, led_cdev->blink_brightness);
+		led_trigger_event(input_events_led_trigger, LED_FULL);
 		data->led_on = true;
 	}
 	data->led_off_time = jiffies + led_off_delay;
···
 
 	handle->dev = dev;
 	handle->handler = handler;
-	handle->name = "input-events";
+	handle->name = KBUILD_MODNAME;
 
 	ret = input_register_handle(handle);
 	if (ret)
···
 	{ }
 };
 
-static int input_events_activate(struct led_classdev *led_cdev)
+static struct input_handler input_events_handler = {
+	.name = KBUILD_MODNAME,
+	.event = input_events_event,
+	.connect = input_events_connect,
+	.disconnect = input_events_disconnect,
+	.id_table = input_events_ids,
+};
+
+static int __init input_events_init(void)
 {
-	struct input_events_data *data;
 	int ret;
 
-	data = kzalloc(sizeof(*data), GFP_KERNEL);
-	if (!data)
-		return -ENOMEM;
+	INIT_DELAYED_WORK(&input_events_data.work, led_input_events_work);
+	spin_lock_init(&input_events_data.lock);
 
-	data->handler.name = "input-events";
-	data->handler.event = input_events_event;
-	data->handler.connect = input_events_connect;
-	data->handler.disconnect = input_events_disconnect;
-	data->handler.id_table = input_events_ids;
+	led_trigger_register_simple("input-events", &input_events_led_trigger);
 
-	INIT_DELAYED_WORK(&data->work, led_input_events_work);
-	spin_lock_init(&data->lock);
-
-	data->led_cdev = led_cdev;
-	data->led_cdev_saved_flags = led_cdev->flags;
-	data->led_off_delay = msecs_to_jiffies(DEFAULT_LED_OFF_DELAY_MS);
-
-	/*
-	 * Use led_cdev->blink_brightness + LED_BLINK_SW flag so that sysfs
-	 * brightness writes will change led_cdev->new_blink_brightness for
-	 * configuring the on state brightness (like ledtrig-heartbeat).
-	 */
-	if (!led_cdev->blink_brightness)
-		led_cdev->blink_brightness = led_cdev->max_brightness;
-
-	/* Start with LED off */
-	led_set_brightness_nosleep(data->led_cdev, LED_OFF);
-
-	ret = input_register_handler(&data->handler);
+	ret = input_register_handler(&input_events_handler);
 	if (ret) {
-		kfree(data);
+		led_trigger_unregister_simple(input_events_led_trigger);
 		return ret;
 	}
 
-	set_bit(LED_BLINK_SW, &led_cdev->work_flags);
-
-	/* Turn LED off during suspend, original flags are restored on deactivate() */
-	led_cdev->flags |= LED_CORE_SUSPENDRESUME;
-
-	led_set_trigger_data(led_cdev, data);
 	return 0;
 }
 
-static void input_events_deactivate(struct led_classdev *led_cdev)
+static void __exit input_events_exit(void)
 {
-	struct input_events_data *data = led_get_trigger_data(led_cdev);
-
-	led_cdev->flags = data->led_cdev_saved_flags;
-	clear_bit(LED_BLINK_SW, &led_cdev->work_flags);
-	input_unregister_handler(&data->handler);
-	cancel_delayed_work_sync(&data->work);
-	kfree(data);
+	input_unregister_handler(&input_events_handler);
+	cancel_delayed_work_sync(&input_events_data.work);
+	led_trigger_unregister_simple(input_events_led_trigger);
 }
 
-static struct led_trigger input_events_led_trigger = {
-	.name       = "input-events",
-	.activate   = input_events_activate,
-	.deactivate = input_events_deactivate,
-	.groups     = input_events_led_groups,
-};
-module_led_trigger(input_events_led_trigger);
+module_init(input_events_init);
+module_exit(input_events_exit);
 
 MODULE_AUTHOR("Hans de Goede <[e-mail]>");
 MODULE_DESCRIPTION("Input Events LED trigger");