INFO: rcu detected stall in discover_timer

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 70e88c758a6b selftests/bpf: fix bpf_flow.c build
git tree: bpf-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15eb86c6400000
kernel config: https://syzkaller.appspot.com/x/.config?x=8f59875069d721b6
dashboard link: https://syzkaller.appspot.com/bug?extid=a2845eaf6c025f6d0454
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [ax...@kernel.dk ed.c...@acm.org
linux...@vger.kernel.org linux-...@vger.kernel.org]

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a2845e...@syzkaller.appspotmail.com

Total swap = 0kB
1965979 pages RAM
0 pages HighMem/MovableOnly
343324 pages reserved
0 pages cma reserved
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 0-....: (1 GPs behind) idle=c86/1/0x4000000000000004
softirq=69850/69851 fqs=6
rcu: (t=10502 jiffies g=91033 q=87)
NMI backtrace for cpu 0
CPU: 0 PID: 1550 Comm: syz-executor0 Not tainted 4.19.0-rc2+ #96
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1c4/0x2b4 lib/dump_stack.c:113
nmi_cpu_backtrace.cold.3+0x63/0xa2 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1b3/0x1ed lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
trigger_single_cpu_backtrace include/linux/nmi.h:162 [inline]
rcu_dump_cpu_stacks+0x175/0x1c2 kernel/rcu/tree.c:1340
print_cpu_stall.cold.78+0x2d3/0x524 kernel/rcu/tree.c:1478
check_cpu_stall kernel/rcu/tree.c:1550 [inline]
__rcu_pending kernel/rcu/tree.c:3276 [inline]
rcu_pending kernel/rcu/tree.c:3319 [inline]
rcu_check_callbacks+0xfd9/0x1990 kernel/rcu/tree.c:2665
update_process_times+0x2d/0x70 kernel/time/timer.c:1636
tick_sched_handle+0x9f/0x180 kernel/time/tick-sched.c:164
tick_sched_timer+0x45/0x130 kernel/time/tick-sched.c:1274
__run_hrtimer kernel/time/hrtimer.c:1398 [inline]
__hrtimer_run_queues+0x41c/0x10d0 kernel/time/hrtimer.c:1460
hrtimer_interrupt+0x313/0x780 kernel/time/hrtimer.c:1518
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1029 [inline]
smp_apic_timer_interrupt+0x1a1/0x760 arch/x86/kernel/apic/apic.c:1054
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:864
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:788
[inline]
RIP: 0010:slab_alloc_node mm/slab.c:3329 [inline]
RIP: 0010:kmem_cache_alloc_node+0x247/0x730 mm/slab.c:3642
Code: 40 7e 0f 85 32 ff ff ff e8 e5 d2 3e ff e9 28 ff ff ff e8 fc 2f c3 ff
48 83 3d 9c 7e b0 07 00 0f 84 33 01 00 00 4c 89 ff 57 9d <0f> 1f 44 00 00
e9 bf fe ff ff 31 d2 be a5 01 00 00 48 c7 c7 f2 7a
RSP: 0000:ffff8801dac073d8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000000 RBX: 0000000000480020 RCX: 1ffff10026e511e9
RDX: 0000000000000000 RSI: ffff880137288f50 RDI: 0000000000000282
RBP: ffff8801dac07448 R08: ffff880137288f48 R09: 0000000000000002
R10: 0000000000000000 R11: ffff880137288680 R12: ffff8801d9be7680
R13: ffff8801d9be7680 R14: 0000000000000000 R15: 0000000000000282
__alloc_skb+0x119/0x770 net/core/skbuff.c:193
alloc_skb include/linux/skbuff.h:997 [inline]
new_skb+0x26/0x1c0 drivers/block/aoe/aoecmd.c:67
aoecmd_cfg_pkts drivers/block/aoe/aoecmd.c:426 [inline]
aoecmd_cfg+0x279/0x7f0 drivers/block/aoe/aoecmd.c:1374
discover_timer+0x50/0x60 drivers/block/aoe/aoemain.c:24
call_timer_fn+0x272/0x920 kernel/time/timer.c:1326
expire_timers kernel/time/timer.c:1363 [inline]
__run_timers+0x7e5/0xc70 kernel/time/timer.c:1682
run_timer_softirq+0x52/0xb0 kernel/time/timer.c:1695
__do_softirq+0x30b/0xad8 kernel/softirq.c:292
invoke_softirq kernel/softirq.c:372 [inline]
irq_exit+0x17f/0x1c0 kernel/softirq.c:412
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x1cb/0x760 arch/x86/kernel/apic/apic.c:1056
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:864
</IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:788
[inline]
RIP: 0010:slab_alloc mm/slab.c:3385 [inline]
RIP: 0010:kmem_cache_alloc+0x297/0x730 mm/slab.c:3552
Code: 7e 0f 85 cf fe ff ff e8 46 b3 3e ff e9 c5 fe ff ff e8 5d 10 c3 ff 48
83 3d fd 5e b0 07 00 0f 84 3b 03 00 00 48 8b 7d d0 57 9d <0f> 1f 44 00 00
e9 54 fe ff ff 31 d2 be a5 01 00 00 48 c7 c7 f2 7a
RSP: 0000:ffff88019de7f748 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000000 RBX: 0000000000480020 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff880137288f00 RDI: 0000000000000282
RBP: ffff88019de7f7b0 R08: ffff880137288680 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff8801d9be7680 R14: ffff8801d9be7680 R15: 0000000000480020
skb_clone+0x1bb/0x500 net/core/skbuff.c:1283
____bpf_clone_redirect net/core/filter.c:2075 [inline]
bpf_clone_redirect+0xb9/0x490 net/core/filter.c:2062
bpf_prog_dc6f81d0b0097db7+0x81d/0x1000
aoe: skb alloc failure


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
syzbot.