Message-ID: <CACT4Y+YSQjskV--E7AjTRc4UrwXG3TkhM7L8NNdsOqLPPTbrEg@mail.gmail.com>
Date:   Thu, 10 Dec 2020 09:53:17 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+cdb28ae22d09b2142434@...kaller.appspotmail.com>
Cc:     Frédéric Weisbecker <fweisbec@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: INFO: rcu detected stall in tasklet_action_common

On Wed, Dec 9, 2020 at 10:53 PM syzbot
<syzbot+cdb28ae22d09b2142434@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    b3298500 Merge tag 'for-5.10/dm-fixes' of git://git.kernel..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=135a07ab500000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e49433cfed49b7d9
> dashboard link: https://syzkaller.appspot.com/bug?extid=cdb28ae22d09b2142434
> compiler:       gcc (GCC) 10.1.0-syz 20200507
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17b43345500000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=102d68df500000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+cdb28ae22d09b2142434@...kaller.appspotmail.com

The reproducer is basically just perf_event_open:

r0 = perf_event_open(&(0x7f0000000500)={0x1, 0x70, 0x0, 0x0, 0x0, 0x0,
0x0, 0x1, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, @perf_bp={0x0}}, 0x0,
0xffffffffffffffff, 0xffffffffffffffff, 0x0)
fcntl$setstatus(r0, 0x4, 0x42000)

I guess it's the old case of perf starving the system with some
effective busy looping due to small sampling period (?).

Peter, IIRC you had some patches to make lower bound controllable or
something. Were they ever merged? Maybe we need to tune some sysctl's
on syzbot?



> rcu: INFO: rcu_preempt self-detected stall on CPU
> rcu:    0-...!: (10194 ticks this GP) idle=25a/1/0x4000000000000000 softirq=8880/8882 fqs=1
>         (t=10502 jiffies g=8805 q=65)
> rcu: rcu_preempt kthread starved for 10501 jiffies! g8805 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: 8880 Comm: syz-executor561 Not tainted 5.10.0-rc6-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
>  run_sysvec_on_irqstack_cond arch/x86/include/asm/irq_stack.h:91 [inline]
>  sysvec_apic_timer_interrupt+0x48/0x100 arch/x86/kernel/apic/apic.c:1091
>  asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:631
> RIP: 0010:__ieee80211_rx_handle_packet net/mac80211/rx.c:4568 [inline]
> RIP: 0010:ieee80211_rx_list+0x9fc/0x23d0 net/mac80211/rx.c:4759
> Code: d2 0f 85 8d 17 00 00 48 8b 44 24 10 bf 50 00 00 00 0f b7 00 41 89 c4 66 89 44 24 08 66 41 81 e4 fc 00 44 89 e6 e8 e4 36 21 f9 <66> 41 83 fc 50 0f 84 be 11 00 00 e8 a4 3e 21 f9 44 89 e6 bf 80 00
> RSP: 0018:ffffc90000007cb8 EFLAGS: 00000246
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff884ec5cc
> RDX: 0000000000000080 RSI: ffff88801b054ec0 RDI: 0000000000000003
> RBP: ffff88801a9ae140 R08: 0000000000000001 R09: ffffc90000007d48
> R10: 0000000000000050 R11: 0000000000000001 R12: 0000000000000080
> R13: ffff88801a9ae140 R14: ffff88801a650c80 R15: ffffc90000007d48
>  ieee80211_rx_napi+0xf7/0x3d0 net/mac80211/rx.c:4780
>  ieee80211_rx include/net/mac80211.h:4502 [inline]
>  ieee80211_tasklet_handler+0xd3/0x130 net/mac80211/main.c:235
>  tasklet_action_common.constprop.0+0x22f/0x2d0 kernel/softirq.c:560
>  __do_softirq+0x2a0/0x9f6 kernel/softirq.c:298
>  asm_call_irq_on_stack+0xf/0x20
>  </IRQ>
>  __run_on_irqstack arch/x86/include/asm/irq_stack.h:26 [inline]
>  run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:77 [inline]
>  do_softirq_own_stack+0xaa/0xd0 arch/x86/kernel/irq_64.c:77
>  invoke_softirq kernel/softirq.c:393 [inline]
>  __irq_exit_rcu kernel/softirq.c:423 [inline]
>  irq_exit_rcu+0x132/0x200 kernel/softirq.c:435
>  sysvec_apic_timer_interrupt+0x4d/0x100 arch/x86/kernel/apic/apic.c:1091
>  asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:631
> RIP: 0010:__list_del_entry_valid+0xa/0xf0 lib/list_debug.c:39
> Code: fd 48 8b 34 24 eb a1 48 89 f7 48 89 34 24 e8 dd 3c f7 fd 48 8b 34 24 eb b4 0f 1f 80 00 00 00 00 48 b8 00 00 00 00 00 fc ff df <41> 55 41 54 55 48 89 fd 48 83 c7 08 48 89 fa 48 c1 ea 03 80 3c 02
> RSP: 0018:ffffc9000206fab0 EFLAGS: 00000293
> RAX: dffffc0000000000 RBX: ffffc9000217fb70 RCX: ffffffff8163ffc3
> RDX: ffff88801b054ec0 RSI: ffffffff83d03751 RDI: ffffc9000217fb88
> RBP: ffffc9000217fb78 R08: 0000000000000001 R09: ffff88801be61a63
> R10: 0000000000000000 R11: 0000000000000000 R12: ffffc9000217fb88
> R13: ffffc90000dfe148 R14: ffffc9000217fb90 R15: 00000000006e3000
>  __list_del_entry include/linux/list.h:132 [inline]
>  list_del_init include/linux/list.h:204 [inline]
>  plist_del+0x1ad/0x480 lib/plist.c:130
>  __unqueue_futex+0xc9/0x1b0 kernel/futex.c:1440
>  mark_wake_futex+0x10f/0x1a0 kernel/futex.c:1458
>  futex_wake+0x3b4/0x490 kernel/futex.c:1618
>  do_futex+0x322/0x1a60 kernel/futex.c:3770
>  __do_sys_futex+0x2a2/0x470 kernel/futex.c:3828
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x448969
> Code: e8 4c 09 03 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 05 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f9c01bc6cf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
> RAX: ffffffffffffffda RBX: 00000000006e39e8 RCX: 0000000000448969
> RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 00000000006e39ec
> RBP: 00000000006e39e0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006e39ec
> R13: 00007ffd71e0be4f R14: 00007f9c01bc79c0 R15: 00000000006e39ec
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches
>
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