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linux/drivers/leds
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Remi Pommarel 966fdfc453 leds: Fix LED_OFF brightness race 
[ Upstream commit 2c70953b6f ]

While commit fa15d8c692 ("leds: Fix set_brightness_delayed() race")
successfully forces led_set_brightness() to be called with LED_OFF at
least once when switching from blinking to LED on state so that
hw-blinking can be disabled, another race remains. Indeed in
led_set_brightness(LED_OFF) followed by led_set_brightness(any)
scenario the following CPU scheduling can happen:

    CPU0                                     CPU1
    ----                                     ----
 set_brightness_delayed() {
   test_and_clear_bit(BRIGHTNESS_OFF)
                                         led_set_brightness(LED_OFF) {
                                           set_bit(BRIGHTNESS_OFF)
					   queue_work()
                                         }
                                         led_set_brightness(any) {
                                           set_bit(BRIGHTNESS)
					   queue_work() //already queued
                                         }
   test_and_clear_bit(BRIGHTNESS)
     /* LED set with brightness any */
 }

 /* From previous CPU1 queue_work() */
 set_brightness_delayed() {
   test_and_clear_bit(BRIGHTNESS_OFF)
     /* LED turned off */
   test_and_clear_bit(BRIGHTNESS)
     /* Clear from previous run, LED remains off */

In that case the led_set_brightness(LED_OFF)/led_set_brightness(any)
sequence will be effectively executed in reverse order and LED will
remain off.

With the introduction of commit 32360bf6a5 ("leds: Introduce ordered
workqueue for LEDs events instead of system_wq") the race is easier to
trigger as sysfs brightness configuration does not wait for
set_brightness_delayed() work to finish (flush_work() removal).

Use delayed_set_value to optionnally re-configure brightness after a
LED_OFF. That way a LED state could be configured more that once but
final state will always be as expected. Ensure that delayed_set_value
modification is seen before set_bit() using smp_mb__before_atomic().

Fixes: fa15d8c692 ("leds: Fix set_brightness_delayed() race")
Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/19c81177059dab7b656c42063958011a8e4d1a66.1740050412.git.repk@triplefau.lt
Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-04-10 14:37:32 +02:00
..
blink leds: bcm63138: Rename dependency symbol ARCH_BCM4908 to ARCH_BCMBCA 2023-07-28 09:59:58 +01:00
flash leds: flash: mt6360: Fix device_for_each_child_node() refcounting in error paths 2024-12-09 10:33:08 +01:00
rgb pwm: Rename pwm_apply_state() to pwm_apply_might_sleep() 2024-06-12 11:12:24 +02:00
simple - Core Frameworks 2023-09-04 13:52:58 -07:00
trigger leds: triggers: Flush pending brightness before activating trigger 2024-08-11 12:47:14 +02:00
Kconfig leds: aw2013: Select missing dependency REGMAP_I2C 2024-01-25 15:35:49 -08:00
led-class-flash.c led-class-flash: fix -Wrestrict warning 2021-09-27 16:09:42 +02:00
led-class-multicolor.c leds: multicolor: Use rounded division when calculating color components 2023-08-17 11:25:03 +01:00
led-class.c leds: class: Protect brightness_show() with led_cdev->led_access mutex 2024-12-14 20:00:12 +01:00
led-core.c leds: Fix LED_OFF brightness race 2025-04-10 14:37:32 +02:00
led-triggers.c leds: triggers: Flush pending brightness before activating trigger 2024-08-11 12:47:14 +02:00
leds-88pm860x.c leds: various: use only available OF children 2020-09-26 21:56:39 +02:00
leds-acer-a500.c leds: Add driver for Acer Iconia Tab A500 2020-09-26 21:56:42 +02:00
leds-adp5520.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 149 2019-05-30 11:25:18 -07:00
leds-an30259a.c leds: an30259a: Use devm_mutex_init() for mutex initialization 2024-07-11 12:49:02 +02:00
leds-apu.c leds: apu: extend support for PC Engines APU1 with newer firmware 2021-02-19 22:15:10 +01:00
leds-ariel.c leds: Explicitly include correct DT includes 2023-07-28 10:02:32 +01:00
leds-aw200xx.c leds: aw200xx: Fix write to DIM parameter 2024-01-25 15:35:49 -08:00
leds-aw2013.c leds: aw2013: Unlock mutex before destroying it 2024-03-26 18:19:55 -04:00
leds-bcm6328.c leds: bcm6328: Get rid of custom led_init_default_state_get() 2023-01-30 08:03:37 +00:00
leds-bcm6358.c leds: bcm6358: Get rid of custom led_init_default_state_get() 2023-01-30 08:03:38 +00:00
leds-bd2606mvv.c leds: bd2606mvv: Fix device child node usage in bd2606mvv_probe() 2024-10-04 16:29:27 +02:00
leds-bd2802.c leds: Switch i2c drivers back to use .probe() 2023-05-25 12:16:22 +01:00
leds-blinkm.c leds: blinkm: Replace all non-returning strlcpy with strscpy 2023-05-25 12:31:18 +01:00
leds-cht-wcove.c leds: cht-wcove: Use devm_led_classdev_register() to avoid memory leak 2025-02-08 09:51:56 +01:00
leds-clevo-mail.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
leds-cobalt-qube.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
leds-cobalt-raq.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 1 2019-05-21 11:28:39 +02:00
leds-cpcap.c leds: Explicitly include correct DT includes 2023-07-28 10:02:32 +01:00
leds-cr0014114.c leds: Explicitly include correct DT includes 2023-07-28 10:02:32 +01:00
leds-da903x.c leds: da903x: fix use-after-free on unbind 2020-06-22 10:37:58 +02:00
leds-da9052.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
leds-dac124s085.c spi: make remove callback a void function 2022-02-09 13:00:45 +00:00
leds-el15203000.c spi: make remove callback a void function 2022-02-09 13:00:45 +00:00
leds-gpio-register.c leds: leds-gpio-register: Supply description for param 'id' 2021-05-28 11:38:54 +02:00
leds-gpio.c leds: gpio: Configure per-LED pin control 2023-05-25 12:34:30 +01:00
leds-hp6xx.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
leds-ip30.c leds: ip30: Convert to devm_platform_ioremap_resource() 2023-07-28 09:26:21 +01:00
leds-ipaq-micro.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
leds-is31fl32xx.c leds: Explicitly include correct DT includes 2023-07-28 10:02:32 +01:00
leds-is31fl319x.c leds: Switch i2c drivers back to use .probe() 2023-05-25 12:16:22 +01:00
leds-lm355x.c leds: Switch i2c drivers back to use .probe() 2023-05-25 12:16:22 +01:00
leds-lm3530.c leds: Switch i2c drivers back to use .probe() 2023-05-25 12:16:22 +01:00
leds-lm3532.c leds: Switch i2c drivers back to use .probe() 2023-05-25 12:16:22 +01:00
leds-lm3533.c leds: use sysfs_emit() to instead of scnprintf() 2022-12-07 21:05:20 +01:00
leds-lm3642.c leds: Switch i2c drivers back to use .probe() 2023-05-25 12:16:22 +01:00
leds-lm3692x.c leds: Switch i2c drivers back to use .probe() 2023-05-25 12:16:22 +01:00
leds-lm3697.c leds: Switch i2c drivers back to use .probe() 2023-05-25 12:16:22 +01:00
leds-lm36274.c leds: lm36274: Add missed property.h 2021-05-30 23:03:48 +02:00
leds-locomo.c ARM: pxa: split up mach/hardware.h 2022-04-19 16:27:05 +02:00
leds-lp50xx.c leds: Switch i2c drivers back to use .probe() 2023-05-25 12:16:22 +01:00
leds-lp55xx-common.c leds: lp55xx: Remove redundant test for invalid channel number 2024-12-09 10:33:05 +01:00
leds-lp55xx-common.h leds: lp55xx: Add multicolor framework support to lp55xx 2020-07-22 14:42:06 +02:00
leds-lp3944.c leds: Switch i2c drivers back to use .probe() 2023-05-25 12:16:22 +01:00
leds-lp3952.c leds: Switch i2c drivers back to use .probe() 2023-05-25 12:16:22 +01:00
leds-lp5521.c leds: Remove redundant of_match_ptr() 2023-08-17 13:28:25 +01:00
leds-lp5523.c leds: Remove redundant of_match_ptr() 2023-08-17 13:28:25 +01:00
leds-lp5562.c leds: Remove redundant of_match_ptr() 2023-08-17 13:28:25 +01:00
leds-lp8501.c leds: Remove redundant of_match_ptr() 2023-08-17 13:28:25 +01:00
leds-lp8788.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
leds-lp8860.c leds: lp8860: Write full EEPROM, not only half of it 2025-02-17 09:40:14 +01:00
leds-lt3593.c leds: lt3593: Put fwnode in any case during ->probe() 2021-08-03 23:49:31 +02:00
leds-max8997.c leds: max8997: Don't error if there is no pdata 2022-10-22 11:55:03 +02:00
leds-max77650.c leds: parse linux,default-trigger DT property in LED core 2020-09-26 21:56:43 +02:00
leds-mc13783.c leds: various: use only available OF children 2020-09-26 21:56:39 +02:00
leds-menf21bmc.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
leds-mlxcpld.c leds: leds-mlxcpld: Fix a bunch of kernel-doc formatting issues 2021-05-28 11:39:00 +02:00
leds-mlxreg.c leds: mlxreg: Use devm_mutex_init() for mutex initialization 2024-11-22 15:38:37 +01:00
leds-mt6323.c leds: leds-mt6323: Adjust return/parameter types in wled get/set callbacks 2023-06-23 10:57:14 +01:00
leds-net48xx.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
leds-netxbig.c leds: netxbig: Fix an OF node reference leak in netxbig_leds_get_of_pdata() 2025-02-08 09:51:52 +01:00
leds-nic78bx.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157 2019-05-30 11:26:37 -07:00
leds-ns2.c leds: ns2: Slightly simplify a memory allocation 2023-07-28 11:58:04 +01:00
leds-ot200.c leds: leds-ot200: Use devm_led_classdev_register 2015-11-03 08:59:13 +01:00
leds-pca955x.c leds: Switch i2c drivers back to use .probe() 2023-05-25 12:16:22 +01:00
leds-pca963x.c leds: Switch i2c drivers back to use .probe() 2023-05-25 12:16:22 +01:00
leds-pca995x.c leds: pca995x: Fix device child node usage in pca995x_probe() 2024-10-04 16:29:29 +02:00
leds-pca9532.c leds: Explicitly include correct DT includes 2023-07-28 10:02:32 +01:00
leds-pm8058.c leds: Explicitly include correct DT includes 2023-07-28 10:02:32 +01:00
leds-powernv.c leds: various: use only available OF children 2020-09-26 21:56:39 +02:00
leds-pwm.c leds: pwm: Disable PWM when going to suspend 2024-06-12 11:12:24 +02:00
leds-rb532.c leds: rb532: cleanup whitespace 2020-01-02 22:41:53 +01:00
leds-regulator.c leds: regulator: Make probeable from device tree 2022-05-05 10:04:52 +02:00
leds-sc27xx-bltc.c leds: various: use only available OF children 2020-09-26 21:56:39 +02:00
leds-spi-byte.c leds: spi-byte: Call of_node_put() on error path 2024-09-12 11:11:30 +02:00
leds-ss4200.c leds: ss4200: Convert PCIBIOS_* return codes to errnos 2024-08-03 08:54:18 +02:00
leds-sunfire.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
leds-syscon.c leds: Explicitly include correct DT includes 2023-07-28 10:02:32 +01:00
leds-tca6507.c leds: Switch i2c drivers back to use .probe() 2023-05-25 12:16:22 +01:00
leds-ti-lmu-common.c leds: Explicitly include correct DT includes 2023-07-28 10:02:32 +01:00
leds-tlc591xx.c leds: Explicitly include correct DT includes 2023-07-28 10:02:32 +01:00
leds-tps6105x.c leds: tps6105x: add driver for MFD chip LED mode 2019-12-21 20:10:02 +01:00
leds-turris-omnia.c leds: turris-omnia: Do not use SMBUS calls 2023-11-20 11:59:24 +01:00
leds-wm831x-status.c leds: Use DEVICE_ATTR_{RW, RO, WO} macros 2020-12-30 19:37:13 +01:00
leds-wm8350.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
leds-wrap.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
leds.h leds: Move led_init_default_state_get() to the global header 2023-01-30 08:03:35 +00:00
Makefile leds: pca995x: Add support for PCA995X chips 2023-07-28 09:26:28 +01:00
TODO leds: TODO: Add documentation about possible subsystem improvements 2020-09-30 19:15:33 +02:00
uleds.c leds: uleds: Use module_misc_device macro to simplify the code 2023-08-18 11:42:54 +01:00