4.11-rc7 crash when booting with 1 numa node?

4.11-rc7 crash when booting with 1 numa node?

[Darrick J. Wong]

Hi,

When booting 4.11-rc7 on a qemu guest with a single numa node, I hit the
following[1] crash on boot.  If I configure more than one node, the
problem goes away.  I tracked the relevant line down to:

(gdb) l *(irq_create_affinity_masks+0x237)
0xffffffff81103a87 is in irq_create_affinity_masks
(/raid/home/djwong/cdev/work/linux-xfs/kernel/irq/affinity.c:111).
106                     /* Calculate the number of cpus per vector */
107                     ncpus = cpumask_weight(nmsk);
108                     vecs_to_assign = min(vecs_per_node, ncpus);
109
110                     /* Account for rounding errors */
111                     extra_vecs = ncpus - vecs_to_assign * (ncpus / vecs_to_assign);
112
113                     for (v = 0; curvec < last_affv && v < vecs_to_assign;
114                          curvec++, v++) {
115                             cpus_per_vec = ncpus / vecs_to_assign;

Not sure exactly what's going on here; I can look into it more tomorrow
at work but maybe this rings a bell already?  The line in question was
last changed by commit 3412386b53 ("irq/affinity: Fix extra vecs
calculation"). :)

Thanks,

--Darrick

[1] relevant dmesg:

[    0.823932] divide error: 0000 [#1] PREEMPT SMP
[    0.824818] Modules linked in:
[    0.825469] CPU: 3 PID: 1 Comm: swapper/0 Not tainted 4.11.0-rc7-xfsx #1
[    0.826673] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[    0.828137] task: ffff880078ff4f80 task.stack: ffffc9000031c000
[    0.829096] RIP: 0010:irq_create_affinity_masks+0x237/0x360
[    0.830004] RSP: 0000:ffffc9000031faa0 EFLAGS: 00010297
[    0.830849] RAX: 0000000000000004 RBX: 0000000000000000 RCX: 0000000000000004
[    0.831988] RDX: 0000000000000000 RSI: 0000000000000040 RDI: 000000000000000f
[    0.833137] RBP: ffffc9000031fb10 R08: 0000000000000000 R09: 0000000000000001
[    0.834296] R10: 0000000000000000 R11: 0000000000000001 R12: ffffc9000031fcb8
[    0.835453] R13: 0000000000000004 R14: 000000000000a018 R15: 0000000000000002
[    0.836589] FS:  0000000000000000(0000) GS:ffff88007f600000(0000) knlGS:0000000000000000
[    0.837948] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    0.838881] CR2: 00000000ffffffff CR3: 0000000001c11000 CR4: 00000000000006e0
[    0.840029] Call Trace:
[    0.840454]  __pci_enable_msix+0x316/0x4c0
[    0.841133]  pci_alloc_irq_vectors_affinity+0xd6/0x170
[    0.842020]  vp_find_vqs_msix+0xee/0x470
[    0.842739]  vp_find_vqs+0x36/0x180
[    0.843490]  ? __kmalloc+0x27c/0x2e0
[    0.844095]  virtscsi_init+0xfd/0x280
[    0.844718]  ? vp_get+0x59/0x80
[    0.845266]  virtscsi_probe+0xeb/0x2f0
[    0.845886]  virtio_dev_probe+0x19d/0x200
[    0.846547]  driver_probe_device+0x204/0x2e0
[    0.847272]  __driver_attach+0x9f/0xb0
[    0.847878]  ? driver_probe_device+0x2e0/0x2e0
[    0.848750]  bus_for_each_dev+0x66/0xa0
[    0.849419]  driver_attach+0x1e/0x20
[    0.850078]  bus_add_driver+0x1b4/0x230
[    0.850709]  ? scsi_init_procfs+0x5b/0x5b
[    0.851409]  driver_register+0x60/0xe0
[    0.852036]  ? scsi_init_procfs+0x5b/0x5b
[    0.852707]  register_virtio_driver+0x20/0x30
[    0.853456]  init+0x85/0xcc
[    0.853930]  do_one_initcall+0x53/0x1b0
[    0.854585]  ? parse_args+0x26a/0x3f0
[    0.855238]  kernel_init_freeable+0x1d9/0x25c
[    0.855947]  ? rest_init+0x140/0x140
[    0.856553]  kernel_init+0xe/0x100
[    0.857125]  ret_from_fork+0x31/0x40
[    0.857710] Code: c5 80 2a 09 82 48 89 cf 48 89 4d d0 f3 48 0f b8 c7 48 89 c1 8b 45 a0 44 29 f8 99 f7 7d a8 39 c8 0f 4f c1 89 c3 89 45 bc 89 c8 99 <f7> fb 44 39 7d c4 89 55 b8 89 45 ac 0f 8e b4 00 00 00 85 db 0f 
[    0.861065] RIP: irq_create_affinity_masks+0x237/0x360 RSP: ffffc9000031faa0
[    0.862531] ---[ end trace e472b3c89b58d381 ]---
[    0.863311] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
[    0.863311] 
[    0.864840] Kernel Offset: disabled
[    0.865433] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
[    0.865433]