Subject: linux-next: qemu boot failure after merge of the tip tree

From: Stephen Rothwell <[email-masked]>
Date: Mon, 1 Feb 2021 20:09:18 +1100

Hi all,

After merging the tip tree, today's linux-next qemu boot test (powerpc
pseries_le_defconfig) failed like this:

[    0.005355][    T1] smp: Brought up 1 node, 1 CPU
[    0.005415][    T1] numa: Node 0 CPUs: 0
[    0.005496][    T1] BUG: Unable to handle kernel instruction fetch (NULL pointer?)
[    0.005559][    T1] Faulting instruction address: 0x00000000
[    0.005613][    T1] Oops: Kernel access of bad area, sig: 11 [#1]
[    0.005665][    T1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
[    0.005719][    T1] Modules linked in:
[    0.005754][    T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.11.0-rc6 #2
[    0.005808][    T1] NIP:  0000000000000000 LR: c0000000001a22ac CTR: 0000000000000001
[    0.005870][    T1] REGS: c0000000063a3860 TRAP: 0480   Not tainted  (5.11.0-rc6)
[    0.005933][    T1] MSR:  8000000002009033 <SF,VEC,EE,ME,IR,DR,RI,LE>  CR: 24002242  XER: 20000000
[    0.006014][    T1] CFAR: c0000000001a22a8 IRQMASK: 0 
[    0.006014][    T1] GPR00: c0000000001a21ac c0000000063a3b00 c000000001439400 0000000000000000 
[    0.006014][    T1] GPR04: 0000000000000000 00000000000000c4 0000000000000001 c000000001509400 
[    0.006014][    T1] GPR08: 0000000000000000 c0000000011f5af0 000000007eaa0000 0000000000000001 
[    0.006014][    T1] GPR12: 0000000000000001 c000000001610000 c000000006350f18 0000000000000001 
[    0.006014][    T1] GPR16: c000000001507bb0 0000000000000000 c0000000012106b0 c00000000146dce0 
[    0.006014][    T1] GPR20: c000000006054a90 0000000000000001 0000000000000000 00000000ffff8ad0 
[    0.006014][    T1] GPR24: 00000000ffff8ad0 c000000006054a00 0000000000000000 c000000006055000 
[    0.006014][    T1] GPR28: 0000000000000000 c000000006350f00 c000000006350f00 c000000001472380 
[    0.006590][    T1] NIP [0000000000000000] 0x0
[    0.006633][    T1] LR [c0000000001a22ac] build_sched_domains+0x47c/0x1500
[    0.006687][    T1] Call Trace:
[    0.006719][    T1] [c0000000063a3b00] [c0000000001a21ac] build_sched_domains+0x37c/0x1500 (unreliable)
[    0.006794][    T1] [c0000000063a3c40] [c0000000001a42d0] sched_init_domains+0xe0/0x120
[    0.006858][    T1] [c0000000063a3c90] [c000000001075f38] sched_init_smp+0x50/0xc4
[    0.006922][    T1] [c0000000063a3cc0] [c0000000010545a4] kernel_init_freeable+0x1d4/0x398
[    0.006987][    T1] [c0000000063a3da0] [c000000000013144] kernel_init+0x2c/0x168
[    0.007051][    T1] [c0000000063a3e10] [c00000000000dff0] ret_from_kernel_thread+0x5c/0x6c
[    0.007116][    T1] Instruction dump:
[    0.007150][    T1] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX 
[    0.007226][    T1] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX 
[    0.007310][    T1] ---[ end trace e117133fa9cbc962 ]---

(full boot log attached)

Presumably caused by commit

  620a6dc40754 ("sched/topology: Make sched_init_numa() use a set for the deduplicating sort")

I note a similar report from the kernel test robot on LKML.

I have reverted that commit for today (which fixed the boot failure).

-- 
Cheers,
Stephen Rothwell