Created attachment 303277 [details]
kernel dmesg (6.0.9, PowerMac G4 DP)

Encountered this on my PowerMac G4 DP while building glibc in a session via TigerVNC.

[...]
BUG: spinlock trylock failure on UP on CPU#0, Xvnc/256
 lock: 0xd9651008, .magic: dead4ead, .owner: Xvnc/256, .owner_cpu: 0
CPU: 0 PID: 256 Comm: Xvnc Tainted: G                T  6.0.9-gentoo-PMacG4 #1
Call Trace:
[f2b91c80] [c05d2d0c] dump_stack_lvl+0x34/0x74 (unreliable)
[f2b91ca0] [c008f95c] do_raw_spin_trylock+0xac/0xb8
[f2b91cc0] [c0937a3c] _raw_spin_trylock+0x10/0x44
[f2b91cd0] [c02204e4] z3fold_zpool_free+0x410/0x594
[f2b91d10] [c01f5810] zswap_free_entry+0xd8/0x198
[f2b91d30] [c01f5a28] zswap_frontswap_invalidate_page+0xec/0xf0
[f2b91d50] [c01f4be4] __frontswap_invalidate_page+0x5c/0xd4
[f2b91d70] [c01effd4] swapcache_free_entries+0x310/0x478
[f2b91dc0] [c01f45a0] free_swap_slot+0x138/0x158
[f2b91de0] [c01efc68] put_swap_page+0xb8/0x114
[f2b91e00] [c01ec758] delete_from_swap_cache+0x78/0xe8
[f2b91e20] [c01f0694] try_to_free_swap+0xf0/0x13c
[f2b91e40] [c01c4c1c] do_swap_page+0x594/0x9d8
[f2b91e80] [c01c5b44] handle_mm_fault+0x760/0xe34
[f2b91f00] [c001eaa0] do_page_fault+0x1c0/0x814
[f2b91f30] [c000433c] DataAccess_virt+0x124/0x17c
--- interrupt: 300 at 0xa7183884
NIP:  a7183884 LR: a71837e4 CTR: a71838f4
REGS: f2b91f40 TRAP: 0300   Tainted: G                T   (6.0.9-gentoo-PMacG4)
MSR:  0000f932 <EE,PR,FP,ME,IR,DR,RI>  CR: 24002428  XER: 20000000
DAR: 017d2750 DSISR: 42000000 
GPR00: 00651904 afccb070 a7e5d5a0 017d2750 00000006 00000070 a72733e0 ff000000 
GPR08: 017d273c 017d2750 a6494c10 a7183698 a71837e4 0072fff4 afccc6a4 afccc6a8 
GPR16: 00734474 0073424c 00734470 00734248 0073446c 00000000 a7e56764 00000000 
GPR24: 00000001 00000006 016f9d50 017d2750 000001b0 017d2750 a72dfff4 a6494c20 
NIP [a7183884] 0xa7183884
LR [a71837e4] 0xa71837e4
--- interrupt: 300[...]
[...]

Some data about the machine:
 # inxi -bZ
System:
  Host: T600 Kernel: 6.0.9-gentoo-PMacG4 arch: ppc bits: 32
    Console: pty pts/0 Distro: Gentoo Base System release 2.9
Machine:
  Type: PPC System: PowerMac3 6 details: N/A
    mobo: PowerMac3,6 MacRISC3 Power Macintosh serial: P6N
CPU:
  Info: single core 7455 altivec supported [UP] speed (MHz): 1417
Graphics:
  Device-1: AMD RV350 [Radeon 9550/9600/X1050 Series] driver: radeon
    v: kernel
  Display: x11 server: X.org v: 1.21.1.4 driver: X: loaded: radeon
    unloaded: fbdev,modesetting gpu: radeon
    resolution: <missing: xdpyinfo/xrandr>
  OpenGL: renderer: softpipe v: 3.3 Mesa 22.2.3
Network:
  Device-1: Broadcom BCM4306 802.11b/g Wireless LAN driver: b43-pci-bridge
  Device-2: Apple UniNorth 2 GMAC driver: gem
  Device-3: gmac driver: gem


The G4 DP got 2 CPUs but I am running it with a single core only due to bug #215389. Another locking bug I got on this machine is bug #216723 (here with a .config utilizing both CPUs). Don't know whether this might be related.