linux-kernel - Re: [Patch v4 10/10] i2x: pnx: Use threaded irq to fix warning from del_timer

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Date: Fri, 21 Jun 2024 14:08:03 +0200
From: Piotr Wojtaszczyk <piotr.wojtaszczyk@...esys.com>
To: Andi Shyti <andi.shyti@...nel.org>
Cc: Vinod Koul <vkoul@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	"J.M.B. Downing" <jonathan.downing@...tel.com>, Vladimir Zapolskiy <vz@...ia.com>, 
	Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>, 
	Russell King <linux@...linux.org.uk>, Michael Turquette <mturquette@...libre.com>, 
	Stephen Boyd <sboyd@...nel.org>, Miquel Raynal <miquel.raynal@...tlin.com>, 
	Richard Weinberger <richard@....at>, Vignesh Raghavendra <vigneshr@...com>, Jaroslav Kysela <perex@...ex.cz>, 
	Takashi Iwai <tiwai@...e.com>, Arnd Bergmann <arnd@...db.de>, Yangtao Li <frank.li@...o.com>, 
	Li Zetao <lizetao1@...wei.com>, Chancel Liu <chancel.liu@....com>, 
	Michael Ellerman <mpe@...erman.id.au>, dmaengine@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	alsa-devel@...a-project.org, linuxppc-dev@...ts.ozlabs.org, 
	linux-sound@...r.kernel.org, linux-clk@...r.kernel.org, 
	linux-i2c@...r.kernel.org, linux-mtd@...ts.infradead.org, 
	Markus Elfring <Markus.Elfring@....de>
Subject: Re: [Patch v4 10/10] i2x: pnx: Use threaded irq to fix warning from del_timer_sync()

Hi Andi,

On Fri, Jun 21, 2024 at 12:57 AM Andi Shyti <andi.shyti@...nel.org> wrote:
> On Thu, Jun 20, 2024 at 07:56:41PM GMT, Piotr Wojtaszczyk wrote:
> > When del_timer_sync() is called in an interrupt context it throws a warning
> > because of potential deadlock. Threaded irq handler fixes the potential
> > problem.
> >
> > Signed-off-by: Piotr Wojtaszczyk <piotr.wojtaszczyk@...esys.com>
>
> did you run into a lockdep splat?
>
> Anything against using del_timer(), instead? Have you tried?

I didn't get a lockdep splat but console was flooded with warnings from
https://github.com/torvalds/linux/blob/v6.10-rc4/kernel/time/timer.c#L1655
In the linux kernel v5.15 I didn't see these warnings.

I'm not a maintainer of the driver and I didn't do any research on
what kind of impact
would have using del_timer() instad. Maybe Vladimir Zapolskiy will know that.

-- 
Piotr Wojtaszczyk
Timesys