linux-kernel - Re: [PREEMPT_RT] 8250 IRQ lockup when flooding serial console (was Re: [ANNOUNCE] v5.4.28-rt19)

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Date:   Thu, 23 Apr 2020 09:06:01 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Jiri Kosina <jikos@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Daniel Wagner <dwagner@...e.de>
Subject: Re: [PREEMPT_RT] 8250 IRQ lockup when flooding serial console (was
 Re: [ANNOUNCE] v5.4.28-rt19)

On Thu, 23 Apr 2020 12:45:59 +0200
Sebastian Andrzej Siewior <bigeasy@...utronix.de> wrote:

> On 2020-04-23 11:12:59 [+0200], Jiri Kosina wrote:
> > On Thu, 23 Apr 2020, Jiri Kosina wrote:
> >   
> > > > I'm pleased to announce the v5.4.28-rt19 patch set.   
> > > 
> > > First, I don't believe this is necessarily a regression coming with this 
> > > particular version, but this is the first kernel where I tried this and it 
> > > crashed.  
> > 
> > I just tried with 5.6.4-rt3, and I can make it explode exactly the same 
> > way:  
> 
> I though I dealt with it. In the past it triggered also with threadirqs
> on !RT but this isn't the case anymore. It still explodes on RT. Let me
> look…

Good, something to look for as a backport ;-)

BTW, I haven't released a new 5.4-rt because the default one is triggering
a large latency somewhere, and makes my tests fail. I'm trying to dig into
the cause when I get time.

-- Steve