Re: [PATCH] leds: avoid races with workqueue

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On 5/2/19 10:06 PM, Pavel Machek wrote:
On Thu 2019-05-02 21:28:06, Jacek Anaszewski wrote:
On 5/2/19 9:13 PM, Pavel Machek wrote:

+++ b/drivers/leds/led-class.c
@@ -57,6 +57,7 @@ static ssize_t brightness_store(struct device *dev,
  	if (state == LED_OFF)
  	led_set_brightness(led_cdev, state);
+	flush_work(&led_cdev->set_brightness_work);

Is this really required here? It creates non-uniform brightness
setting behavior depending on whether it is set from sysfs or
by in-kernel call to led_set_brightness().

This fixes the echo 0 > brightness; echo 1 > brightness. It has to be
at a place where we can sleep.

If you have better idea, it is welcome, but it would be good to fix
the bug.

Currently not, so I applied the patch in this shape.


This is actually something that makes sense for stable.. perhaps the
bots can pick it up.

I was thinking of it, but finally decided to submit this patch
to linux-stable when it will prove not having side effects.

But if you think it is ready for stable then I can add
relevant "Fixes" tag. Do you think that below will be an appropriate
base to refer to?

Fixes 1afcadfcd184 ("leds: core: Use set_brightness_work for the blocking

Yes, that looks right. If you can add fixes: and cc: stable tags, the
rest should happen automagically.

Cc: stable@xxxxxxxxxx is exactly for what it claims - sending a copy
to that list.

"Fixes:" seems to be always enough for the bots to pick a patch.

Tag added.

Best regards,
Jacek Anaszewski

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