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

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Message-ID: <20210322113918.ze52gq54cpsspgej@linutronix.de>
Date:   Mon, 22 Mar 2021 12:39:18 +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 12:34:02 [+0100], Uwe Kleine-König wrote:
> On Mon, Mar 22, 2021 at 12:10:36PM +0100, Johan Hovold wrote:
> > Force-threaded interrupt handlers used to run with interrupts enabled,
> > something which could lead to deadlocks in case a threaded handler
> > shared a lock with code running in hard interrupt context (e.g. timer
> > callbacks) and did not explicitly disable interrupts.
> > 
> > This was specifically the case for serial drivers that take the port
> > lock in their console write path as printk can be called from hard
> > interrupt context also with forced threading ("threadirqs").
> > 
> > Since commit 81e2073c175b ("genirq: Disable interrupts for force
> > threaded handlers") interrupt handlers always run with interrupts
> > disabled on non-RT so that drivers no longer need to do handle this.
> 
> So we're breaking RT knowingly here? If this is the case I'm not happy
> with your change. (And if RT is not affected a different wording would
> be good.)

Which wording, could you be more specific? It looks good from here and
no, RT is not affected.

> Best regards
> Uwe

Sebastian