Created attachment 294829 [details]
kernel dmesg (5.10.10, eMachines E620)

I am hitting this on my laptop (eMachines E620). Half of the time it boots up correctly and would fine for days. The other time boot process stalls due to unknown reasons, so I thought it would be a good idea to build a kernel with some debug output:

[...]
ACPI: Core revision 20200925
clocksource: hpet: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 133484873504 ns
APIC: Switch to symmetric I/O mode setup
..TIMER: vector=0x30 apic1=0 pin1=0 apic2=-1 pin2=-1
------------[ cut here ]------------
DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())
WARNING: CPU: 0 PID: 0 at check_flags+0x4d/0x14c
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.10.10-E620_debug #3
Hardware name: eMachines        eMachines E620  /Nile       , BIOS V1.03       09/30/2008
RIP: 0010:check_flags+0x4d/0x14c
Code: 7d 85 c0 74 72 e8 5a 89 55 00 85 c0 74 1e 83 3d c6 a9 eb 00 00 75 15 48 c7 c6 3a 3c bd 82 48 c7 c7 5d 4b bc 82 e8 02 dc 54 00 <0f> 0b 48 c7 c7 11 3c bd 82 eb 3d 85 c0 75 3e 65 8b 05 df a5 f9 7d
RSP: 0000:ffffffff82e03db0 EFLAGS: 00010082
RAX: 000000000000002f RBX: 0000000000000001 RCX: 0000000000000003
RDX: 000000000000007e RSI: ffffffff82f303b0 RDI: ffffffff82e6aaa0
RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff82e03be0
R10: 0000000000000003 R11: 0000000000000001 R12: 0000000000000000
R13: ffffffff82e24d98 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff943a35e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff943a28e01000 CR3: 0000000067e12000 CR4: 00000000000006b0
Call Trace:
 lock_acquire+0x246/0x30f
 ? mp_irqdomain_activate+0x2c/0x32
 _raw_spin_lock_irqsave+0x39/0x49
 ? ioapic_read_entry+0x16/0x40
 ioapic_read_entry+0x16/0x40
 clear_IO_APIC_pin+0x13/0x123
 setup_IO_APIC+0x2ee/0x76b
 ? ioapic_read_entry+0x37/0x40
 ? clear_IO_APIC_pin+0xf7/0x123
 x86_late_time_init+0x1b/0x2b
 start_kernel+0x3ed/0x47a
 secondary_startup_64_no_verify+0xb0/0xbb
irq event stamp: 717
hardirqs last  enabled at (717): [<ffffffff8317699e>] timer_irq_works+0x28/0xe5
hardirqs last disabled at (716): [<ffffffff8317720c>] setup_IO_APIC+0x1cd/0x76b
softirqs last  enabled at (386): [<ffffffff82039ad2>] irq_enter_rcu+0x38/0x68
softirqs last disabled at (385): [<ffffffff82039ab7>] irq_enter_rcu+0x1d/0x68
---[ end trace 33480a0fe5ebf797 ]---
possible reason: unannotated irqs-off.
irq event stamp: 717
hardirqs last  enabled at (717): [<ffffffff8317699e>] timer_irq_works+0x28/0xe5
hardirqs last disabled at (716): [<ffffffff8317720c>] setup_IO_APIC+0x1cd/0x76b
softirqs last  enabled at (386): [<ffffffff82039ad2>] irq_enter_rcu+0x38/0x68
softirqs last disabled at (385): [<ffffffff82039ab7>] irq_enter_rcu+0x1d/0x68
..MP-BIOS bug: 8254 timer not connected to IO-APIC
...trying to set up timer (IRQ0) through the 8259A ...
..... (found apic 0 pin 0) ...
....... works.
tsc: Marking TSC unstable due to TSCs unsynchronized
[...]

Some data about the machine:
 # inxi -b
System:    Kernel: 5.10.10-E620_debug x86_64 bits: 64 Console: tty 0 
           Distro: Gentoo Base System release 2.7 
Machine:   Type: Laptop System: eMachines product: eMachines E620 v: V1.03 
           serial: xxx 
           Mobo: eMachines model: Nile serial: xxx BIOS: eMachines v: 1.03 
           date: 09/30/2008 
Battery:   ID-1: BAT1 charge: N/A condition: N/A 
CPU:       Info: Dual Core AMD Athlon X2 3250e [MCP] speed: 1496 MHz 
Graphics:  Device-1: AMD RS690M [Radeon Xpress 1200/1250/1270] driver: radeon v: kernel 
           Display: server: X.org 1.20.10 driver: ati,radeon unloaded: fbdev,modesetting tty: 104x53 
           Message: Advanced graphics data unavailable in console for root. 
Network:   Device-1: Qualcomm Atheros AR242x / AR542x Wireless Network Adapter driver: ath5k 
           Device-2: Realtek RTL810xE PCI Express Fast Ethernet driver: r8169 
Drives:    Local Storage: total: 256.17 GiB used: 8.95 GiB (3.5%) 
Info:      Processes: 103 Uptime: 11m Memory: 1.82 GiB used: 103.8 MiB (5.6%) Init: SysVinit 
           rc: OpenRC v: 0.42.1 runlevel: default Shell: Bash inxi: 3.1.06 

 # lscpu 
Architecture:                    x86_64
CPU op-mode(s):                  32-bit, 64-bit
Byte Order:                      Little Endian
Address sizes:                   40 bits physical, 48 bits virtual
CPU(s):                          2
On-line CPU(s) list:             0,1
Thread(s) per core:              1
Core(s) per socket:              2
Socket(s):                       1
Vendor ID:                       AuthenticAMD
CPU family:                      15
Model:                           107
Model name:                      AMD Athlon(tm) X2 Dual Core Processor 3250e
Stepping:                        2
CPU MHz:                         1496.168
BogoMIPS:                        2993.01
Virtualization:                  AMD-V
L1d cache:                       128 KiB
L1i cache:                       128 KiB
L2 cache:                        1 MiB
Vulnerability Itlb multihit:     Not affected
Vulnerability L1tf:              Not affected
Vulnerability Mds:               Not affected
Vulnerability Meltdown:          Not affected
Vulnerability Spec store bypass: Not affected
Vulnerability Spectre v1:        Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2:        Mitigation; Full AMD retpoline, STIBP disabled, RSB filling
Vulnerability Srbds:             Not affected
Vulnerability Tsx async abort:   Not affected
Flags:                           fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36
                                  clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt rdtscp lm 3dno
                                 wext 3dnow rep_good nopl cpuid extd_apicid pni cx16 lahf_lm cmp_legacy 
                                 svm extapic cr8_legacy 3dnowprefetch vmmcall lbrv