linux-kernel - Re: next-20250710: PREEMPT_RT: rcu_preempt self-detected stall on CPU rcu_preempt_deferred_qs

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Message-ID: <CAFwiDX8A=2N9iOOMRE_tzfPLDfsn70bhxDhiFMkyZ1pEMasXiA@mail.gmail.com>
Date: Fri, 11 Jul 2025 14:51:02 +0530
From: Neeraj upadhyay <neeraj.iitr10@...il.com>
To: Naresh Kamboju <naresh.kamboju@...aro.org>
Cc: rcu <rcu@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>, 
	lkft-triage@...ts.linaro.org, Linux Regressions <regressions@...ts.linux.dev>, 
	"Paul E. McKenney" <paulmck@...nel.org>, neeraj.upadhyay@...nel.org, 
	Joel Fernandes <joelagnelf@...dia.com>, Qi Xi <xiqi2@...wei.com>, 
	Xiongfeng Wang <wangxiongfeng2@...wei.com>, Dan Carpenter <dan.carpenter@...aro.org>, 
	Arnd Bergmann <arnd@...db.de>, Anders Roxell <anders.roxell@...aro.org>, 
	Ben Copeland <benjamin.copeland@...aro.org>
Subject: Re: next-20250710: PREEMPT_RT: rcu_preempt self-detected stall on CPU rcu_preempt_deferred_qs_handler

Hi Naresh,

On Fri, Jul 11, 2025 at 12:11 PM Naresh Kamboju
<naresh.kamboju@...aro.org> wrote:
>
> Regressions on boot failure observed in builds with CONFIG_PREEMPT_RT=y
> and CONFIG_LAZY_PREEMPT=y enabled on multiple platforms running the
> Linux next-20250710.
>
> Kernel stalls and RCU preempt self-detected stalls reported.
> Boot log shows CPU stalls and failure as below.
>
> Test environments:
> - Ampere Altra
> - rk3399-rock-pi-4b
> - x86_64
>
> Regression Analysis:
> - New regression? Yes
> - Reproducibility? Yes
>
> Boot regression: next-20250710 rcu_preempt self-detected stall on CPU
> rcu_preempt_deferred_qs_handler
>
> Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>
>

Thanks for the report. We saw the same issue recently. Here is the fixed commit:

https://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux.git/commit/?h=next&id=2e154d164418e1eaadbf5dc58cbf19e7be8fdc67

I have pushed it to rcu next branch:

https://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux.git/log/?h=next



- Neeraj