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: <20251126152637.GDaSccLZVBEOs20n6T@fat_crate.local>
Date: Wed, 26 Nov 2025 16:26:37 +0100
From: Borislav Petkov <bp@...en8.de>
To: iommu@...ts.linux.dev, "Paul E. McKenney" <paulmck@...nel.org>
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
Subject: Re: amd iommu: rcu: INFO: rcu_preempt detected expedited stalls on
 CPUs/tasks: { 0-.... } 8 jiffies s: 113 root: 0x1/.

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.
> 
> Ideas?
> 
> [   12.946913] (journald)[506]: Found cgroup2 on /sys/fs/cgroup/, full unified hierarchy
> [   12.948083] (journald)[506]: Successfully forked off '(sd-mkuserns)' as PID 507.
> [   12.977579] rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 0-.... } 8 jiffies s: 113 root: 0x1/.
> [   12.983638] rcu: blocking rcu_node structures (internal RCU debug): l=1:0-15:0x1/.

And as suspected, booting in it again, it doesn't trigger anymore. But there's
something new in dmesg which looks weird and makes me want to Cc Paul:

[    6.965526] rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: {
[    6.971581] Key type fscrypt-provisioning registered
[    6.975191] PM: Image not found (code -6)
[    6.975631]  } 8 jiffies s: 89 root: 0x0/.


and

[   12.549532] rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 2-.... } 8 jiffies s: 113 root: 0x1/.
[   12.550863] rcu: blocking rcu_node structures (internal RCU debug):

[   12.817601] rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: {
[   12.819773] (sd-mkdcre[520]: Credential search path is: /etc/credstore:/run/credstore:/usr/local/lib/credstore:/usr/lib/credstore
[   12.827074]  } 8 jiffies s: 129 root: 0x0/.

[   12.881508] rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: {
[   12.892854] (sd-mkdcr[522]: Credential search path is: /etc/credstore.encrypted:/run/credstore.encrypted:/usr/local/lib/credstore.encrypted:/usr/lib/credstore.encrypted
[   12.905244]  } 8 jiffies s: 133 root: 0x0/.

Paul, this looks weird.

Why is that issuing empty lists between the { }?

Thx.

-- 
Regards/Gruss,
    Boris.

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