linux-kernel - Re: INFO: rcu detected stall in batadv_nc

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Date:   Thu, 1 Oct 2020 12:46:41 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+69904c3b4a09e8fa2e1b@...kaller.appspotmail.com>,
        mareklindner@...mailbox.ch, sw@...onwunderlich.de, a@...table.cc,
        Sven Eckelmann <sven@...fation.org>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        b.a.t.m.a.n@...ts.open-mesh.org, netdev <netdev@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: INFO: rcu detected stall in batadv_nc_worker (3)

On Thu, Oct 1, 2020 at 12:35 PM syzbot
<syzbot+69904c3b4a09e8fa2e1b@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    fffe3ae0 Merge tag 'for-linus-hmm' of git://git.kernel.org..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=17e03342900000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=226c7a97d80bec54
> dashboard link: https://syzkaller.appspot.com/bug?extid=69904c3b4a09e8fa2e1b
> compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+69904c3b4a09e8fa2e1b@...kaller.appspotmail.com

+batadv maintainers

May be related to:
KMSAN: uninit-value in batadv_nc_worker
https://syzkaller.appspot.com/bug?extid=da9194708de785081f11

> rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
> rcu:    0-...!: (1 GPs behind) idle=22e/1/0x4000000000000000 softirq=85361/85365 fqs=8
>         (detected by 1, t=10502 jiffies, g=114061, q=1511)
> Sending NMI from CPU 1 to CPUs 0:
> NMI backtrace for cpu 0
> CPU: 0 PID: 194 Comm: kworker/u4:4 Not tainted 5.8.0-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Workqueue: bat_events batadv_nc_worker
> RIP: 0010:arch_local_save_flags arch/x86/include/asm/paravirt.h:765 [inline]
> RIP: 0010:arch_local_irq_save arch/x86/include/asm/paravirt.h:787 [inline]
> RIP: 0010:__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:108 [inline]
> RIP: 0010:_raw_spin_lock_irqsave+0x3c/0xc0 kernel/locking/spinlock.c:159
> Code: 03 49 bf 00 00 00 00 00 fc ff df 42 80 3c 38 00 74 0c 48 c7 c7 b0 d5 4b 89 e8 a0 97 92 f9 48 83 3d 38 61 2a 01 00 74 79 9c 58 <0f> 1f 44 00 00 49 89 c6 48 c7 c0 c0 d5 4b 89 48 c1 e8 03 42 80 3c
> RSP: 0018:ffffc90000007d40 EFLAGS: 00000082
> RAX: 0000000000000082 RBX: ffffffff8ba182b8 RCX: 000000000000d6e0
> RDX: 0000000080010001 RSI: ffffffff894eec80 RDI: ffffffff8ba182b8
> RBP: ffffffff894eec80 R08: ffffffff816542f4 R09: fffff52000000fb0
> R10: fffff52000000fb0 R11: 0000000000000000 R12: dffffc0000000000
> R13: 1ffff11015d04ed2 R14: dffffc0000000000 R15: dffffc0000000000
> FS:  0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00000000004ddaf0 CR3: 0000000090ca1000 CR4: 00000000001506f0
> DR0: 0000000020000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
> Call Trace:
>  <IRQ>
>  debug_object_activate+0x62/0x5f0 lib/debugobjects.c:636
>  debug_hrtimer_activate kernel/time/hrtimer.c:416 [inline]
>  debug_activate kernel/time/hrtimer.c:476 [inline]
>  enqueue_hrtimer kernel/time/hrtimer.c:965 [inline]
>  __run_hrtimer kernel/time/hrtimer.c:1537 [inline]
>  __hrtimer_run_queues+0x510/0x930 kernel/time/hrtimer.c:1584
>  hrtimer_interrupt+0x373/0xd60 kernel/time/hrtimer.c:1646
>  local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1080 [inline]
>  __sysvec_apic_timer_interrupt+0xf0/0x260 arch/x86/kernel/apic/apic.c:1097
>  asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706
>  </IRQ>
>  __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
>  run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
>  sysvec_apic_timer_interrupt+0x94/0xf0 arch/x86/kernel/apic/apic.c:1091
>  asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:581
> RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:770 [inline]
> RIP: 0010:lock_release+0x3c4/0x750 kernel/locking/lockdep.c:5026
> Code: 48 c1 e8 03 42 80 3c 28 00 74 0c 48 c7 c7 b8 d5 4b 89 e8 3f 0b 5a 00 48 83 3d df d4 f1 07 00 0f 84 5c 03 00 00 4c 89 e7 57 9d <0f> 1f 44 00 00 65 48 8b 04 25 28 00 00 00 48 3b 44 24 50 0f 85 40
> RSP: 0018:ffffc90001037bf8 EFLAGS: 00000282
> RAX: 1ffffffff1297ab7 RBX: 1ffff110151d2949 RCX: ffff8880a8e94180
> RDX: ffff8880a8e94a48 RSI: ffffffff894ea290 RDI: 0000000000000282
> RBP: 9644b5a36c253f0c R08: dffffc0000000000 R09: fffffbfff131b08e
> R10: fffffbfff131b08e R11: 0000000000000000 R12: 0000000000000282
> R13: dffffc0000000000 R14: dffffc0000000000 R15: ffff8880a8e94a4c
>  rcu_read_unlock include/linux/rcupdate.h:688 [inline]
>  batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:411 [inline]
>  batadv_nc_worker+0x261/0x5c0 net/batman-adv/network-coding.c:718
>  process_one_work+0x789/0xfc0 kernel/workqueue.c:2269
>  worker_thread+0xaa4/0x1460 kernel/workqueue.c:2415
>  kthread+0x37e/0x3a0 drivers/block/aoe/aoecmd.c:1234
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
> rcu: rcu_preempt kthread starved for 10486 jiffies! g114061 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1
> rcu:    Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
> rcu: RCU grace-period kthread stack dump:
> rcu_preempt     I28608    10      2 0x00004000
> Call Trace:
>  context_switch kernel/sched/core.c:3778 [inline]
>  __schedule+0x979/0xce0 kernel/sched/core.c:4527
>
>
> ---
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>
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