The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x ab477b766edd3bfb6321a6e3df4c790612613fae # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024072917-pulsate-subduing-2b97@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

ab477b766edd ("leds: triggers: Flush pending brightness before activating trigger") b1bbd20f35e1 ("leds: trigger: Call synchronize_rcu() before calling trig->activate()") 822c91e72eac ("leds: trigger: Store brightness set by led_trigger_event()") c82a1662d454 ("leds: trigger: Remove unused function led_trigger_rename_static()") 2a5a8fa8b231 ("leds: trigger: use RCU to protect the led_cdevs list") 27af8e2c90fb ("leds: trigger: fix potential deadlock with libata") 93690cdf3060 ("leds: trigger: add support for LED-private device triggers") ec28a8cfdce6 ("leds: core: Remove extern from header") 11f700022137 ("leds: remove PAGE_SIZE limit of /sys/class/leds/<led>/trigger")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From ab477b766edd3bfb6321a6e3df4c790612613fae Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= linux@weissschuh.net Date: Thu, 13 Jun 2024 17:24:51 +0200 Subject: [PATCH] leds: triggers: Flush pending brightness before activating trigger MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

The race fixed in timer_trig_activate() between a blocking set_brightness() call and trigger->activate() can affect any trigger. So move the call to flush_work() into led_trigger_set() where it can avoid the race for all triggers.

Fixes: 0db37915d912 ("leds: avoid races with workqueue") Fixes: 8c0f693c6eff ("leds: avoid flush_work in atomic context") Cc: stable@vger.kernel.org Tested-by: Dustin L. Howett dustin@howett.net Signed-off-by: Thomas Weißschuh linux@weissschuh.net Link: https://lore.kernel.org/r/20240613-led-trigger-flush-v2-1-f4f970799d77@weiss... Signed-off-by: Lee Jones lee@kernel.org

diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c index 59deadb86335..78eb20093b2c 100644 --- a/drivers/leds/led-triggers.c +++ b/drivers/leds/led-triggers.c @@ -201,6 +201,12 @@ int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig) */ synchronize_rcu();

+ /* + * If "set brightness to 0" is pending in workqueue, + * we don't want that to be reordered after ->activate() + */ + flush_work(&led_cdev->set_brightness_work); + ret = 0; if (trig->activate) ret = trig->activate(led_cdev); diff --git a/drivers/leds/trigger/ledtrig-timer.c b/drivers/leds/trigger/ledtrig-timer.c index b4688d1d9d2b..1d213c999d40 100644 --- a/drivers/leds/trigger/ledtrig-timer.c +++ b/drivers/leds/trigger/ledtrig-timer.c @@ -110,11 +110,6 @@ static int timer_trig_activate(struct led_classdev *led_cdev) led_cdev->flags &= ~LED_INIT_DEFAULT_TRIGGER; }

- /* - * If "set brightness to 0" is pending in workqueue, we don't - * want that to be reordered after blink_set() - */ - flush_work(&led_cdev->set_brightness_work); led_blink_set(led_cdev, &led_cdev->blink_delay_on, &led_cdev->blink_delay_off);