linux-kernel - INFO: rcu detected stall in kvm_vcpu

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Message-ID: <000000000000e0d794057592192b@google.com>
Date:   Mon, 10 Sep 2018 22:54:03 -0700
From:   syzbot <syzbot+e9b1e8f574404b6e4ed3@...kaller.appspotmail.com>
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        pbonzini@...hat.com, rkrcmar@...hat.com,
        syzkaller-bugs@...glegroups.com
Subject: INFO: rcu detected stall in kvm_vcpu_ioctl

Hello,

syzbot found the following crash on:

HEAD commit:    3d0e7a9e00fd Merge tag 'md/4.19-rc2' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1666429e400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8f59875069d721b6
dashboard link: https://syzkaller.appspot.com/bug?extid=e9b1e8f574404b6e4ed3
compiler:       gcc (GCC) 8.0.1 20180413 (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+e9b1e8f574404b6e4ed3@...kaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	(detected by 0, t=10502 jiffies, g=45997, q=77)
rcu: All QSes seen, last rcu_preempt kthread activity 10502  
(4294979638-4294969136), jiffies_till_next_fqs=1, root ->qsmask 0x0
syz-executor7   R  running task    22096 16667   5475 0x00000000
Call Trace:
  <IRQ>
  sched_show_task.cold.83+0x2b6/0x30a kernel/sched/core.c:5296
  print_other_cpu_stall.cold.79+0xa83/0xba5 kernel/rcu/tree.c:1430
  check_cpu_stall kernel/rcu/tree.c:1557 [inline]
  __rcu_pending kernel/rcu/tree.c:3276 [inline]
  rcu_pending kernel/rcu/tree.c:3319 [inline]
  rcu_check_callbacks+0xafc/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
  </IRQ>
RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x0/0x20 kernel/kcov.c:183
Code: a6 fe ff ff 5d c3 0f 1f 40 00 55 0f b7 d6 0f b7 f7 bf 03 00 00 00 48  
89 e5 48 8b 4d 08 e8 88 fe ff ff 5d c3 66 0f 1f 44 00 00 <55> 89 f2 89 fe  
bf 05 00 00 00 48 89 e5 48 8b 4d 08 e8 6a fe ff ff
RSP: 0018:ffff88019baf7858 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000000 RBX: ffff88019ef30700 RCX: ffffc90001ed4000
RDX: 0000000000040000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffff88019baf78d8 R08: ffff8801bd9ea700 R09: 1ffffffff12b43cd
R10: ffff88019baf7860 R11: ffff8801dae23993 R12: 0000000000000000
R13: 0000000000000007 R14: 0000000000000007 R15: dffffc0000000000
  kvm_vcpu_ioctl+0x72b/0x1150 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2590
  vfs_ioctl fs/ioctl.c:46 [inline]
  file_ioctl fs/ioctl.c:501 [inline]
  do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
  ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
  __do_sys_ioctl fs/ioctl.c:709 [inline]
  __se_sys_ioctl fs/ioctl.c:707 [inline]
  __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457099
Code: fd b4 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 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f8361215c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f83612166d4 RCX: 0000000000457099
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000006
RBP: 00000000009300a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004cf730 R14: 00000000004c59b9 R15: 0000000000000000
rcu: rcu_preempt kthread starved for 10502 jiffies! g45997 f0x2  
RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: RCU grace-period kthread stack dump:
rcu_preempt     R  running task    22872    10      2 0x80000000
Call Trace:
  context_switch kernel/sched/core.c:2825 [inline]
  __schedule+0x86c/0x1ed0 kernel/sched/core.c:3473
  schedule+0xfe/0x460 kernel/sched/core.c:3517
  schedule_timeout+0x140/0x260 kernel/time/timer.c:1804
  rcu_gp_kthread+0x9d9/0x2310 kernel/rcu/tree.c:2194
  kthread+0x35a/0x420 kernel/kthread.c:246
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413
sched: RT throttling activated


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