linux-kernel - Re: amd iommu: rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 0-.... } 8 jiffies s: 113 root: 0x1/.

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Message-ID: <d90a3959-eacd-495e-99cd-836d07955912@paulmck-laptop>
Date: Thu, 4 Dec 2025 12:42:52 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Borislav Petkov <bp@...en8.de>
Cc: iommu@...ts.linux.dev, Joerg Roedel <joro@...tes.org>,
	Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
	Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
	linux-kernel@...r.kernel.org
Subject: Re: amd iommu: rcu: INFO: rcu_preempt detected expedited stalls on
 CPUs/tasks: { 0-.... } 8 jiffies s: 113 root: 0x1/.

On Thu, Dec 04, 2025 at 03:45:05PM +0100, Borislav Petkov wrote:
> On Wed, Dec 03, 2025 at 09:16:37AM -0800, Paul E. McKenney wrote:
> > Or to some value that works for you.  But if you are not looking to be
> > an expedited RCU CPU stall-warning pioneer, yes, setting it to zero is
> > a good approach.
> > 
> > If you would like to be a more sane pioneer, setting it to (say) 11000
> > (or 11 seconds) could be appropriate.  But what fun is sanity?  ;-)
> 
> Oh, I have a lot of excitement even without RCU experiments. :-P

;-) ;-) ;-)

> But if you need me to try things, lemme know.
> 
> For now I've simply reset the values as to what defconfig sets them to:
> 
> CONFIG_RCU_CPU_STALL_TIMEOUT=21
> CONFIG_RCU_EXP_CPU_STALL_TIMEOUT=0

Sounds good, and thank you!

							Thanx, Paul

> Thx.
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette