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: <499db877-2587-46cf-96cc-486ec66db3df@amd.com>
Date: Thu, 27 Nov 2025 10:45:28 +0530
From: Vasant Hegde <vasant.hegde@....com>
To: Borislav Petkov <bp@...en8.de>, iommu@...ts.linux.dev
Cc: 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, Jason Gunthorpe <jgg@...dia.com>
Subject: Re: amd iommu: rcu: INFO: rcu_preempt detected expedited stalls on
 CPUs/tasks: { 0-.... } 8 jiffies s: 113 root: 0x1/.

Hi Boris,

On 11/26/2025 9:30 PM, Borislav Petkov wrote:
> + Vasant.
> 
> On Wed, Nov 26, 2025 at 03:32:19PM +0100, Borislav Petkov wrote:
>> Hi,
>>
>> this is latest Linus + latest tip/master. Box is Zen3. CCing AMD IOMMU folks
>> because the backtrace points to it.

I have tried tip/master on my Zen3 and I didn't hit this issue. Can you pass
your config file?

We haven't touched that code path recently and generally it should work fine. At
least we shouldn't hit issues under normal condition.

Having said that recently we observed that under really stressed environment we
hit softlock in the culprit code path. We are working on moving wait_on_sem()
out of spinlock.

-Vasant