linux-kernel - Re: [PATCH v1] ASoC: meson: axg-fifo: set option to use raw spinlock

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Message-ID: <7dfdade5-3a57-4883-bfac-067c50ec0ffb@sirena.org.uk>
Date: Mon, 29 Jul 2024 16:28:56 +0100
From: Mark Brown <broonie@...nel.org>
To: Jerome Brunet <jbrunet@...libre.com>
Cc: Arseniy Krasnov <avkrasnov@...utedevices.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Kevin Hilman <khilman@...libre.com>,
	Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
	alsa-devel@...a-project.org, linux-sound@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kernel@...rdevices.ru, oxffffaa@...il.com
Subject: Re: [PATCH v1] ASoC: meson: axg-fifo: set option to use raw spinlock

On Mon, Jul 29, 2024 at 05:06:50PM +0200, Jerome Brunet wrote:
> On Mon 29 Jul 2024 at 15:44, Mark Brown <broonie@...nel.org> wrote:

> > I don't recall this coming up much TBH.  It may be that people just set
> > raw spinlocks when they need it, or that there's not many people using
> > relevant devices with RT kernels.

> I have not been playing much with RT TBH, but AFAIK, with RT irq
> handlers are threaded unless IRQF_NO_THREAD is set. In this case,
> something preemptible in the handler should not be a problem.

> The axg-fifo drivers do not have IRQF_NO_THREAD so something is a bit
> unclear here.

Yeah, it's definitely likely to happen all the time for people using RT
with relevant devices.  I'm not sure I have a good sense of if it's
likely to be a nasty surprise to switch raw spinlocks on by default when
it's currently controllable, I'd expect it'll generally be fine but it's
possibly a bit rude to any users that don't use interrupts...

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