INFO: rcu detected stall in sched_ttwu_pending

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 58fce206 Linux 4.19.78
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17e644c7600000
kernel config: https://syzkaller.appspot.com/x/.config?x=385b97bfadb400be
dashboard link: https://syzkaller.appspot.com/bug?extid=bfb19511b4e6baa292c8
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

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+bfb195...@syzkaller.appspotmail.com

dlm: no local IP address has been set
dlm: cannot start dlm lowcomms -107
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 1-...!: (1 ticks this GP) idle=94e/1/0x4000000000000002
softirq=86135/86135 fqs=0
rcu: (t=11141 jiffies g=115657 q=779)
rcu: rcu_preempt kthread starved for 11141 jiffies! g115657 f0x0
RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1
rcu: RCU grace-period kthread stack dump:
rcu_preempt I29104 10 2 0x80000000
Call Trace:
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x866/0x1dc0 kernel/sched/core.c:3515
schedule+0x92/0x1c0 kernel/sched/core.c:3559
schedule_timeout+0x4db/0xfc0 kernel/time/timer.c:1804
rcu_gp_kthread+0xd5c/0x2190 kernel/rcu/tree.c:2202
kthread+0x354/0x420 kernel/kthread.c:246
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
NMI backtrace for cpu 1
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.19.78 #0
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+0x172/0x1f0 lib/dump_stack.c:113
nmi_cpu_backtrace.cold+0x63/0xa4 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1b0/0x1f8 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:164 [inline]
rcu_dump_cpu_stacks+0x189/0x1d5 kernel/rcu/tree.c:1340
print_cpu_stall kernel/rcu/tree.c:1478 [inline]
check_cpu_stall kernel/rcu/tree.c:1550 [inline]
__rcu_pending kernel/rcu/tree.c:3293 [inline]
rcu_pending kernel/rcu/tree.c:3336 [inline]
rcu_check_callbacks.cold+0x5e3/0xd90 kernel/rcu/tree.c:2682
update_process_times+0x32/0x80 kernel/time/timer.c:1636
tick_sched_handle+0xa2/0x190 kernel/time/tick-sched.c:164
tick_sched_timer+0x47/0x130 kernel/time/tick-sched.c:1274
__run_hrtimer kernel/time/hrtimer.c:1398 [inline]
__hrtimer_run_queues+0x33b/0xdc0 kernel/time/hrtimer.c:1460
hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1518
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1067 [inline]
smp_apic_timer_interrupt+0x111/0x550 arch/x86/kernel/apic/apic.c:1092
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:893
</IRQ>
RIP: 0010:sched_ttwu_pending+0x0/0x210 kernel/sched/core.c:1728
Code: 00 e9 5f ff ff ff 4c 89 c7 e8 5c bc 57 00 e9 f6 fe ff ff e8 f2 bc 57
00 4c 8b 85 70 ff ff ff e9 c2 fe ff ff 66 0f 1f 44 00 00 <55> 48 89 e5 41
57 41 56 4c 8d b5 78 ff ff ff 41 55 4c 8d 7d d8 49
RSP: 0018:ffff8880aa27fd68 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: ffff8880aa2703c0 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff816014c3 RDI: ffff8880aa270c3c
RBP: ffff8880aa27fe18 R08: ffff8880aa2703c0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
R13: ffffffff88724650 R14: ffff8880aa2703c0 R15: ffff8880aa2703c0
cpu_startup_entry+0xc8/0xe0 kernel/sched/idle.c:369
start_secondary+0x3e8/0x5b0 arch/x86/kernel/smpboot.c:271
secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.