Date:   Tue, 15 Dec 2020 11:44:11 -0800
From:   syzbot <syzbot+d4d47d10526314a4f4cb@...kaller.appspotmail.com>
To:     fweisbec@...il.com, linux-kernel@...r.kernel.org, mingo@...nel.org,
        syzkaller-bugs@...glegroups.com, tglx@...utronix.de
Subject: INFO: rcu detected stall in dput (4)

Hello,

syzbot found the following issue on:

HEAD commit:    33dc9614 Merge tag 'ktest-v5.10-rc6' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1426d433500000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3416bb960d5c705d
dashboard link: https://syzkaller.appspot.com/bug?extid=d4d47d10526314a4f4cb
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=179a240f500000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12c81937500000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d4d47d10526314a4f4cb@...kaller.appspotmail.com

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (10493 ticks this GP) idle=4ae/1/0x4000000000000000 softirq=20089/20090 fqs=0 
	(t=10500 jiffies g=24993 q=7)
rcu: rcu_preempt kthread starved for 10500 jiffies! g24993 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:29512 pid:   11 ppid:     2 flags:0x00004000
Call Trace:
 context_switch kernel/sched/core.c:3779 [inline]
 __schedule+0x893/0x2130 kernel/sched/core.c:4528
 schedule+0xcf/0x270 kernel/sched/core.c:4606
 schedule_timeout+0x148/0x250 kernel/time/timer.c:1871
 rcu_gp_fqs_loop kernel/rcu/tree.c:1925 [inline]
 rcu_gp_kthread+0xb4c/0x1c90 kernel/rcu/tree.c:2099
 kthread+0x3b1/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296
NMI backtrace for cpu 0
CPU: 0 PID: 14966 Comm: syz-executor610 Not tainted 5.10.0-rc7-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+0x107/0x163 lib/dump_stack.c:118
 nmi_cpu_backtrace.cold+0x44/0xd7 lib/nmi_backtrace.c:105
 nmi_trigger_cpumask_backtrace+0x1b3/0x230 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
 rcu_dump_cpu_stacks+0x1e3/0x21e kernel/rcu/tree_stall.h:331
 print_cpu_stall kernel/rcu/tree_stall.h:563 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:637 [inline]
 rcu_pending kernel/rcu/tree.c:3694 [inline]
 rcu_sched_clock_irq.cold+0x472/0xee8 kernel/rcu/tree.c:2567
 update_process_times+0x77/0xd0 kernel/time/timer.c:1709
 tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:176
 tick_sched_timer+0x1d1/0x2a0 kernel/time/tick-sched.c:1328
 __run_hrtimer kernel/time/hrtimer.c:1519 [inline]
 __hrtimer_run_queues+0x1ce/0xea0 kernel/time/hrtimer.c:1583
 hrtimer_interrupt+0x334/0x940 kernel/time/hrtimer.c:1645
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1080 [inline]
 __sysvec_apic_timer_interrupt+0x146/0x540 arch/x86/kernel/apic/apic.c:1097
 asm_call_irq_on_stack+0xf/0x20
 </IRQ>
 __run_sysvec_on_irqstack arch/x86/include/asm/irq_stack.h:37 [inline]
 run_sysvec_on_irqstack_cond arch/x86/include/asm/irq_stack.h:89 [inline]
 sysvec_apic_timer_interrupt+0xbd/0x100 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:631
RIP: 0010:kvm_wait arch/x86/kernel/kvm.c:854 [inline]
RIP: 0010:kvm_wait+0x9c/0xd0 arch/x86/kernel/kvm.c:831
Code: 02 48 89 da 83 e2 07 38 d0 7f 04 84 c0 75 32 0f b6 03 41 38 c4 75 13 e8 32 52 46 00 e9 07 00 00 00 0f 00 2d 96 06 19 08 fb f4 <e8> 1f 52 46 00 eb af c3 e9 07 00 00 00 0f 00 2d 80 06 19 08 f4 eb
RSP: 0018:ffffc9000ab97c90 EFLAGS: 00000202
RAX: 000000000000acef RBX: ffff88814221fb08 RCX: ffffffff8155a917
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000246 R08: 0000000000000001 R09: ffffffff8ebaf69f
R10: fffffbfff1d75ed3 R11: 0000000000000000 R12: 0000000000000003
R13: ffffed1028443f61 R14: 0000000000000001 R15: ffff8880b9e356c0
 pv_wait arch/x86/include/asm/paravirt.h:564 [inline]
 pv_wait_head_or_lock kernel/locking/qspinlock_paravirt.h:470 [inline]
 __pv_queued_spin_lock_slowpath+0x8b8/0xb40 kernel/locking/qspinlock.c:508
 pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:554 [inline]
 queued_spin_lock_slowpath arch/x86/include/asm/qspinlock.h:51 [inline]
 queued_spin_lock include/asm-generic/qspinlock.h:85 [inline]
 do_raw_spin_lock+0x200/0x2b0 kernel/locking/spinlock_debug.c:113
 spin_lock include/linux/spinlock.h:354 [inline]
 dentry_kill fs/dcache.c:710 [inline]
 dput+0x941/0xbc0 fs/dcache.c:878
 __fput+0x3ab/0x920 fs/file_table.c:294
 task_work_run+0xdd/0x190 kernel/task_work.c:151
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:164 [inline]
 exit_to_user_mode_prepare+0x17e/0x1a0 kernel/entry/common.c:191
 syscall_exit_to_user_mode+0x38/0x260 kernel/entry/common.c:266
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x406b01
Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 24 1a 00 00 c3 48 83 ec 08 e8 6a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 b3 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007ffde6771d20 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 00007ffde6771d60 RCX: 0000000000406b01
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 0000000000000004 R08: 0000006400000340 R09: 0000006400000340
R10: 00007ffde6771d60 R11: 0000000000000293 R12: 000000000000002d
R13: 0000000000000006 R14: 00000000006e2a1c R15: 0000000000000001


---
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