linux-kernel - Re: [RFC V2 12/21] rv/reactor: Add the printk reactor

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Date:   Wed, 16 Feb 2022 09:58:50 +0100
From:   Daniel Bristot de Oliveira <bristot@...nel.org>
To:     John Ogness <john.ogness@...utronix.de>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     Jonathan Corbet <corbet@....net>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Marco Elver <elver@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Gabriele Paoloni <gpaoloni@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Clark Williams <williams@...hat.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-trace-devel@...r.kernel.org
Subject: Re: [RFC V2 12/21] rv/reactor: Add the printk reactor

On 2/15/22 20:33, John Ogness wrote:
>> I saw deadlocks in the past, and while testing the WIP monitor some
>> time ago, it seems it depends on the console type. If such restriction
>> does not exist anymore, I can remove that comment, it would be even
>> better!
> If you say it depended on the console type, then it was probably the
> framebuffer console that was at fault. The fbcon is a landmine for
> deadlocks, which is why PREEMPT_RT avoids fbcon printing from
> non-preemptible context. For mainline, the series is currently in
> review.
> 
> Perhaps avoiding fbcon would be good enough for you to avoid deadlocks
> with this reactor using printk().

So, I will keep printk(), add a depends on *!* fbcon, and remove the comment.
What do you think?

-- Daniel