linux-kernel - Re: commit 3d5bfbd97163 versus -rt

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Message-ID: <37e28373-c6ec-2602-ec5c-cb0b65ce6697@prevas.dk>
Date:   Tue, 15 Jun 2021 18:24:20 +0200
From:   Rasmus Villemoes <rasmus.villemoes@...vas.dk>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        linux-rt-users@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Esben Haabendal <esben@...nix.com>
Subject: Re: commit 3d5bfbd97163 versus -rt

On 15/06/2021 17.57, Rasmus Villemoes wrote:
> On 15/06/2021 17.33, Steven Rostedt wrote:
>> On Tue, 15 Jun 2021 14:35:27 +0200
>> Rasmus Villemoes <rasmus.villemoes@...vas.dk> wrote:
>>
>>> Reverting commit 3d5bfbd9716318b1ca5c38488aa69f64d38a9aa5 (gpio:
>>> mpc8xxx: change the gpio interrupt flags.) makes it go away, as does
>>> disabling CONFIG_PREEMPT_RT or simply booting a vanilla v5.10.42 (where
>>> that option exists but cannot be selected).
>>
>> I'm curious if it will also trigger on vanilla v5.10.42 but add to the
>> kernel command line: threadirqs
>>
>> Make sure you have CONFIG_IRQ_FORCED_THREADING set too.
>>
>> Because it appears to be an issue with that being called by the generic
>> threaded irq infrastructure, which PREEMPT_RT enables automatically.
> 
> It doesn't:
> 
> ~ # uname -r
> 5.10.42-00001-g10216cf63a12
> ~ # grep -ow threadirqs /proc/cmdline
> threadirqs
> ~ # zcat /proc/config.gz | grep FORCED_THREADING
> CONFIG_IRQ_FORCED_THREADING=y
> ~ # dmesg | grep WARNING
> ~ #

And as an extra data point, it also doesn't trigger on 5.10.41-rt42
configured without PREEMPT_RT but with threadirqs on the command line.

Rasmus