INFO: rcu detected stall in call_timer_fn (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 32ee7492 Linux 4.19.101
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1273bda5e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=928a6b2d3f9b21f8
dashboard link: https://syzkaller.appspot.com/bug?extid=38f08ac9d2a051c22ee4
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+38f08a...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 1-...!: (1 GPs behind) idle=83e/1/0x4000000000000004 softirq=95948/95950 fqs=65
rcu: (t=10500 jiffies g=125337 q=1466)
rcu: rcu_preempt kthread starved for 10362 jiffies! g125337 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: RCU grace-period kthread stack dump:
rcu_preempt R running task 29104 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:1806
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: 10715 Comm: syz-executor.3 Not tainted 4.19.101-syzkaller #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+0x197/0x210 lib/dump_stack.c:118
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:1638
tick_sched_handle+0xa2/0x190 kernel/time/tick-sched.c:168
tick_sched_timer+0x47/0x130 kernel/time/tick-sched.c:1278
__run_hrtimer kernel/time/hrtimer.c:1401 [inline]
__hrtimer_run_queues+0x33b/0xdc0 kernel/time/hrtimer.c:1463
hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1521
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
RIP: 0010:debug_lockdep_rcu_enabled kernel/rcu/update.c:253 [inline]
RIP: 0010:rcu_read_lock_sched_held+0x3d/0x130 kernel/rcu/update.c:111
Code: 89 c1 48 89 e5 53 83 e0 07 48 c1 e9 03 83 c0 03 0f b6 14 11 38 d0 7c 08 84 d2 0f 85 ae 00 00 00 8b 0d b7 1c 75 08 85 c9 74 3b <48> c7 c3 c0 57 3c 89 48 b8 00 00 00 00 00 fc ff df 48 89 da 48 c1
RSP: 0018:ffff8880ae907d00 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000003 RBX: 0000000000000000 RCX: 0000000000000002
RDX: 0000000000000000 RSI: ffffffff815b53fd RDI: 0000000000000001
RBP: ffff8880ae907d08 R08: ffff88801e0e2080 R09: ffff88801e0e2920
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000100
R13: ffff8880ae907db0 R14: 1ffff11015d20fa6 R15: 0000000000000000
trace_timer_expire_exit include/trace/events/timer.h:121 [inline]
call_timer_fn+0x632/0x720 kernel/time/timer.c:1327
expire_timers kernel/time/timer.c:1363 [inline]
__run_timers kernel/time/timer.c:1684 [inline]
__run_timers kernel/time/timer.c:1652 [inline]
run_timer_softirq+0x64f/0x16a0 kernel/time/timer.c:1697
__do_softirq+0x25c/0x921 kernel/softirq.c:292
invoke_softirq kernel/softirq.c:372 [inline]
irq_exit+0x180/0x1d0 kernel/softirq.c:412
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x13b/0x550 arch/x86/kernel/apic/apic.c:1094
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:893
</IRQ>
RIP: 0010:copy_process.part.0+0x182e/0x7a60 kernel/fork.c:1863
Code: df 49 c7 86 20 08 00 00 00 00 00 00 48 89 fa 48 c1 ea 03 0f b6 04 02 84 c0 74 08 3c 03 0f 8e ae 3b 00 00 49 8d be 1c 13 00 00 <48> b8 00 00 00 00 00 fc ff df 41 c7 86 18 13 00 00 00 00 00 00 48
RSP: 0018:ffff888023bcfb90 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000000 RBX: ffff888032a786c0 RCX: ffffc9000c4c1000
RDX: 1ffff1100654f26b RSI: ffffffff813dfa52 RDI: ffff888032a7935c
RBP: ffff888023bcfda8 R08: 1ffff1100654f210 R09: 0000000000000000
R10: ffffed100654f216 R11: ffff888032a790b7 R12: ffff888032a790d8
R13: ffff888032a78540 R14: ffff888032a78040 R15: ffff888032a78740
copy_process kernel/fork.c:1694 [inline]
_do_fork+0x257/0xfd0 kernel/fork.c:2207
__do_sys_clone kernel/fork.c:2314 [inline]
__se_sys_clone kernel/fork.c:2308 [inline]
__x64_sys_clone+0xbf/0x150 kernel/fork.c:2308
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45b399
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f05f11aec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007f05f11af6d4 RCX: 000000000045b399
RDX: 9999999999999999 RSI: 0000000000000000 RDI: 0000002102001ffc
RBP: 000000000075bf20 R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000070 R14: 00000000004c1c24 R15: 000000000075bf2c


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[syzbot]

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