Subject: commit 3284e4adca9b causes hang on boot with CONFIG_PREEMPT_RT=y

From: Bert Karwatzki <[email-masked]>
Date: Sat, 12 Jul 2025 01:00:41 +0200

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")

Reverting this commit in next-20250711 fixes the issue for me.

Hardware:
$ lspci -nn
00:00.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Renoir/Cezanne Root Complex [1022:1630]
00:00.2 IOMMU [0806]: Advanced Micro Devices, Inc. [AMD] Renoir/Cezanne IOMMU [1022:1631]
00:01.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Renoir PCIe Dummy Host Bridge [1022:1632]
00:01.1 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Renoir PCIe GPP Bridge [1022:1633]
00:02.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Renoir PCIe Dummy Host Bridge [1022:1632]
00:02.1 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Renoir/Cezanne PCIe GPP Bridge [1022:1634]
00:02.2 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Renoir/Cezanne PCIe GPP Bridge [1022:1634]
00:02.3 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Renoir/Cezanne PCIe GPP Bridge [1022:1634]
00:02.4 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Renoir/Cezanne PCIe GPP Bridge [1022:1634]
00:08.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Renoir PCIe Dummy Host Bridge [1022:1632]
00:08.1 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD] Renoir Internal PCIe GPP Bridge to Bus [1022:1635]
00:14.0 SMBus [0c05]: Advanced Micro Devices, Inc. [AMD] FCH SMBus Controller [1022:790b] (rev 51)
00:14.3 ISA bridge [0601]: Advanced Micro Devices, Inc. [AMD] FCH LPC Bridge [1022:790e] (rev 51)
00:18.0 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Cezanne Data Fabric; Function 0 [1022:166a]
00:18.1 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Cezanne Data Fabric; Function 1 [1022:166b]
00:18.2 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Cezanne Data Fabric; Function 2 [1022:166c]
00:18.3 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Cezanne Data Fabric; Function 3 [1022:166d]
00:18.4 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Cezanne Data Fabric; Function 4 [1022:166e]
00:18.5 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Cezanne Data Fabric; Function 5 [1022:166f]
00:18.6 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Cezanne Data Fabric; Function 6 [1022:1670]
00:18.7 Host bridge [0600]: Advanced Micro Devices, Inc. [AMD] Cezanne Data Fabric; Function 7 [1022:1671]
01:00.0 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD/ATI] Navi 10 XL Upstream Port of PCI Express Switch [1002:1478] (rev c3)
02:00.0 PCI bridge [0604]: Advanced Micro Devices, Inc. [AMD/ATI] Navi 10 XL Downstream Port of PCI Express Switch [1002:1479]
03:00.0 Display controller [0380]: Advanced Micro Devices, Inc. [AMD/ATI] Navi 23 [Radeon RX 6600/6600 XT/6600M] [1002:73ff] (rev c3)
03:00.1 Audio device [0403]: Advanced Micro Devices, Inc. [AMD/ATI] Navi 21/23 HDMI/DP Audio Controller [1002:ab28]
04:00.0 Network controller [0280]: MEDIATEK Corp. MT7921K (RZ608) Wi-Fi 6E 80MHz [14c3:0608]
05:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8111/8168/8211/8411 PCI Express Gigabit Ethernet Controller [10ec:8168] (rev 15)
06:00.0 Non-Volatile memory controller [0108]: Kingston Technology Company, Inc. KC3000/FURY Renegade NVMe SSD [E18] [2646:5013] (rev 01)
07:00.0 Non-Volatile memory controller [0108]: Micron/Crucial Technology P1 NVMe PCIe SSD[Frampton] [c0a9:2263] (rev 03)
08:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Cezanne [Radeon Vega Series / Radeon Vega Mobile Series] [1002:1638] (rev c5)
08:00.1 Audio device [0403]: Advanced Micro Devices, Inc. [AMD/ATI] Renoir Radeon High Definition Audio Controller [1002:1637]
08:00.2 Encryption controller [1080]: Advanced Micro Devices, Inc. [AMD] Family 17h (Models 10h-1fh) Platform Security Processor [1022:15df]
08:00.3 USB controller [0c03]: Advanced Micro Devices, Inc. [AMD] Renoir/Cezanne USB 3.1 [1022:1639]
08:00.4 USB controller [0c03]: Advanced Micro Devices, Inc. [AMD] Renoir/Cezanne USB 3.1 [1022:1639]
08:00.5 Multimedia controller [0480]: Advanced Micro Devices, Inc. [AMD] Audio Coprocessor [1022:15e2] (rev 01)
08:00.6 Audio device [0403]: Advanced Micro Devices, Inc. [AMD] Family 17h/19h/1ah HD Audio Controller [1022:15e3]
08:00.7 Signal processing controller [1180]: Advanced Micro Devices, Inc. [AMD] Sensor Fusion Hub [1022:15e4]

$ head /proc/cpuinfo 
processor	: 0
vendor_id	: AuthenticAMD
cpu family	: 25
model		: 80
model name	: AMD Ryzen 7 5800H with Radeon Graphics
stepping	: 0
microcode	: 0xa50000c
cpu MHz		: 2826.830
cache size	: 512 KB
physical id	: 0

Bert Karwatzki