linux-kernel - Re: [PATCH] serial: imx: drop workaround for forced irq threading

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Message-ID: <20210322204836.i4ksobvp6hxl5owh@linutronix.de>
Date:   Mon, 22 Mar 2021 21:48:36 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc:     Johan Hovold <johan@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sam Nobs <samuel.nobs@...tradio.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] serial: imx: drop workaround for forced irq threading

On 2021-03-22 14:40:32 [+0100], Uwe Kleine-König wrote:
> From a strictly logically point of view you indeed cannot. But if you go
> to the street and say to people there that they can park their car in
> this street free of charge between Monday and Friday, I expect that most
> of them will assume that they have to pay for parking on weekends.

If I hear that parking is free on weekdays and on paid on weekends, I
expect it to be a scam.

Uwe, the patch reverts a change which was needed for !RT + threadirqs.
The commit message claims that since the referenced commit "… interrupt
handlers always run with interrupts disabled on non-RT… ". This has
nothing to do with _this_ change. It argues why the workaround is not
needed.
If the referenced commit breaks RT then this is another story.

> So when you said that on on-RT the reason why it used to need a
> workaround is gone made me wonder what that implies for RT.

There was never reason (or a lockdep splat) for it on RT. If so you
should have seen it, right?

Sebastian