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Date: Thu, 8 Feb 2018 22:50:41 +0100
From: Pavel Machek <pavel@ucw.cz>
To: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Cc: linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org,
        craig.mcqueen@innerrange.com.au, Hans de Goede <hdegoede@redhat.com>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
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        Dan Murphy <dmurphy@ti.com>,
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        =?iso-8859-1?Q?C=E9dric?= Le Goater <clg@kaod.org>,
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        Javier Martinez Canillas <javier@dowhile0.org>,
        Colin King <colin.king@canonical.com>
Subject: Re: [PATCH] led: core: Fix race on software blink cancellation
Message-ID: <20180208215041.GA31216@amd>
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Hi!

> Any comments? I'd like to have some acks before applying
> this patch.

I can't say I like it.

> > Commit d23a22a74fde ("leds: delay led_set_brightness if stopping soft-b=
link")
> > made a modifications to the LED core allowing for led_set_brightness() =
to be
> > called from hard-irq context when soft blink is being handled in soft-i=
rq.
> >=20
> > Since that time LED core has undergone modifications related to additio=
n of
> > generic support for delegating brightness setting to a workqueue as wel=
l as
> > subsequent fixes for blink setting use cases.
> >=20
> > After that the LED core code became hard to maintain and analyze, espec=
ially
> > due to the imposed hard-irq context compatibility. It also turned out t=
hat
> > in some cases a LED remained off after executing following sequence of =
commands:
> >=20
> > 1. echo timer > trigger
> > 2. echo 0 > brightness
> > 3. echo 100 > brightness
> >=20
> > The reason was LED_BLINK_DISABLE operation delegated to a set_brightnes=
s_work,
> > triggered in 2., which was handled after 3. took effect.

Could we wait for delayed work to be done before setting the
brightness to fix this one?

									Pavel

--=20
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo=
g.html

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