linux-kernel - Re: [PATCH] leds: trigger: use RCU to protect the led

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Message-ID: <97300681a8e793b71ccedf8224010f1f64da6b5c.camel@sipsolutions.net>
Date:   Mon, 27 Sep 2021 16:20:47 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Pavel Machek <pavel@....cz>
Cc:     linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] leds: trigger: use RCU to protect the led_cdevs list

Hi Pavel,

> > 
> > Cc: stable@...r.kernel.org
> 
> I ... don't like idea of this going to stable.

OK, I guess that's fair. We've been running into the lockdep report for
a while - ever since we made the spinlock in iwlwifi no longer disable
IRQs all the time, which was meant to be a good thing ...

However, the scenario that could cause *real* deadlocks there is really
unlikely and requires four CPUs all doing the exactly right thing,
including a normally very rare *write lock* on the leddev_list_lock, so
I don't think in practice it'll be much of an issue.

johannes