linux-kernel - Re: commit 3284e4adca9b causes hang on boot with CONFIG_PREEMPT

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Message-ID: <21da96d766d92735e5fe022f54d686df8bdfc32d.camel@web.de>
Date: Sat, 12 Jul 2025 01:27:37 +0200
From: Bert Karwatzki <spasswolf@....de>
To: Joel Fernandes <joelagnelf@...dia.com>
Cc: linux-kernel@...r.kernel.org, linux-next@...r.kernel.org, 
	linux-rt-devel@...ts.linux.dev, ankur.a.arora@...cle.com, 
	bobo.shaobowang@...wei.com, boqun.feng@...il.com, frederic@...nel.org, 
	joel@...lfernandes.org, neeraj.upadhyay@...nel.org, paulmck@...nel.org, 
	rcu@...r.kernel.org, urezki@...il.com, wangxiongfeng2@...wei.com, 
	xiexiuqi@...wei.com, xiqi2@...wei.com, spasswolf@....de
Subject: Re: commit 3284e4adca9b causes hang on boot with CONFIG_PREEMPT_RT=y

Am Freitag, dem 11.07.2025 um 19:06 -0400 schrieb Joel Fernandes:
> 
> On 7/11/2025 7:00 PM, Bert Karwatzki wrote:
> > When booting linux next-20250711 (with CONFIG_PREEMPT_RT=y) on my MSI Alpha 15 
> > Laptop running debian sid amd64 the boot process hangs with the last 
> > messages displayed on screen being:
> > 
> > fbcon: amdgpudrmfb (fb0) is primary device
> > Console: switching to colour frame buffer device
> > amdgpu: 0000:08:00.0: [drm]fb0: admgpudrmfb frame buffer device
> > 
> > after some time (about 60s) this error messages appears (hand copied
> > from screen, not entirely accurate)
> > 
> > rcu_preempt self detected stall
> > 
> > with call trace
> > run_irq_workd
> > smpboot_thread_fn
> > kthread
> > ? kthreads_online_cpu
> > ? kthreads_online_cpu
> > ret_from_fork
> > ? kthreads_online_cpu
> > ret_from_fork
> > 
> > This only occurs when compiling with CONFIG_PREEMPT_RT=y.
> > I bisected this and found the first bad commit to be
> > 
> > 3284e4adca9b ("rcu: Fix rcu_read_unlock() deadloop due to IRQ work")
> 
> This commit is still using old code which was fixed in the last day.
> 
> Here is the new commit:
> https://web.git.kernel.org/pub/scm/linux/kernel/git/rcu/linux.git/commit/?h=next&id=2e154d164418e1eaadbf5dc58cbf19e7be8fdc67
> 
> Thanks!
> 
>  - Joel

I already found the new commit, it works!

Bert Karwatzki