Perf hotplug lockup in v4.9-rc8

Mark Rutland
2016-12-07T13:54:24Z

Hi all

Jeremy noticed a kernel lockup on arm64 when the perf tool was used in
parallel with hotplug, which I've reproduced on arm64 and x86(-64) with
v4.9-rc8. In both cases I'm using defconfig; I've tried enabling lockdep
but it was silent for arm64 and x86.

I haven't yet tested earlier kernels and I'm not sure how long this has
been around for; I'm currently building a v4.8 defconfig to compare
with. In the meantime, info dump below.

I'm running:

$ while true; do ./perf stat -e cycles true; done

In parallel with the following script:

---
#!/bin/bash

CPUS=3;

ONLINEFMT="/sys/devices/system/cpu/cpu%s/online";

while true; do
# Don't bother trying CPU0
CPU=$((($RANDOM % $CPUS) + 1))
ONLINEFILE=$(printf $ONLINEFMT $CPU);
echo $(( $RANDOM % 2 )) > $ONLINEFILE;
done
----

After a few successful runs, the perf tool locks up, as does my process
monitor. On arm64 I'm abel to kill the perf tool and make forward
progress, but on x86 my SSH session is dead at this point.

A short while later, I get an RCU stall warning:

[ 4134.743008] INFO: rcu_sched self-detected stall on CPU[ 4134.744023] INFO: rcu_sched detected stalls on CPUs/tasks:
[ 4134.744028] 0-...: (26000 ticks this GP) idle=699/140000000000001/0 softirq=84552/84553 fqs=6491
[ 4134.744029]
[ 4134.744030] (detected by 1, t=26002 jiffies, g=42991, c=42990, q=437)
[ 4134.744032] Task dump for CPU 0:
[ 4134.744033] perf R
[ 4134.744034] running task 13936 5195 3415 0x00000008
ffffc90005ed7d30
[ 4134.744042] ffffffff81095268 ffff8801b73d9040 00000000001d9040 ffff8801a830ead0
[ 4134.744044] 0000000000000139 ffffffff8114454f ffff8801a830ead0 ffff8801b2918400
[ 4134.744047] ffff8801b2918400 ffff8801afa2e000 ffff8801b2918408Call Trace:
[ 4134.744055] [<ffffffff81095268>] ? sched_clock_local+0x18/0x80
[ 4134.744058] [<ffffffff8114454f>] ? perf_install_in_context+0x7f/0x160
[ 4134.744062] [<ffffffff81a8fb29>] ? _raw_spin_unlock_irq+0x29/0x40
[ 4134.744064] [<ffffffff8114454f>] ? perf_install_in_context+0x7f/0x160
[ 4134.744066] [<ffffffff8114b790>] ? __perf_event_enable+0x140/0x140
[ 4134.744068] [<ffffffff8114e8b2>] ? SYSC_perf_event_open+0x512/0xf20
[ 4134.744070] [<ffffffff81151df9>] ? SyS_perf_event_open+0x9/0x10
[ 4134.744072] [<ffffffff81a9026a>] ? entry_SYSCALL_64_fastpath+0x18/0xad
[ 4134.743008] 0-...: (26000 ticks this GP) idle=699/140000000000001/0 softirq=84552/84553 fqs=6519
[ 4134.743008] (t=26123 jiffies g=42991 c=42990 q=437)
[ 4134.743008] Task dump for CPU 0:
[ 4134.743008] perf R running task 13936 5195 3415 0x00000008
[ 4134.743008] ffff8801b7203cf8 ffffffff81091cc7 0000000000000000 0000000000000000
[ 4134.743008] 0000000000000086 ffff8801b7203d10 ffffffff81094db4 ffffffff82062180
[ 4134.743008] ffff8801b7203d40 ffffffff81156f72 ffff8801b73d92c0 ffffffff82062180
[ 4134.743008] Call Trace:
[ 4134.743008] <IRQ> [ 4134.743008] [<ffffffff81091cc7>] sched_show_task+0x117/0x1c0
[ 4134.743008] [<ffffffff81094db4>] dump_cpu_task+0x34/0x40
[ 4134.743008] [<ffffffff81156f72>] rcu_dump_cpu_stacks+0x88/0xc4
[ 4134.743008] [<ffffffff810d25c7>] rcu_check_callbacks+0x8a7/0xa00
[ 4134.743008] [<ffffffff810aae4d>] ? trace_hardirqs_off+0xd/0x10
[ 4134.743008] [<ffffffff81066860>] ? raise_softirq+0x110/0x180
[ 4134.743008] [<ffffffff810e8dc0>] ? tick_sched_do_timer+0x30/0x30
[ 4134.743008] [<ffffffff810d7eca>] update_process_times+0x2a/0x50
[ 4134.743008] [<ffffffff810e8651>] tick_sched_handle.isra.15+0x31/0x40
[ 4134.743008] [<ffffffff810e8df8>] tick_sched_timer+0x38/0x70
[ 4134.743008] [<ffffffff810d8f0f>] __hrtimer_run_queues+0xef/0x510
[ 4134.743008] [<ffffffff810d96f2>] hrtimer_interrupt+0xb2/0x1d0
[ 4134.743008] [<ffffffff8104b171>] hpet_interrupt_handler+0x11/0x30
[ 4134.743008] [<ffffffff810c4c77>] __handle_irq_event_percpu+0x37/0x330
[ 4134.743008] [<ffffffff810c4f8e>] handle_irq_event_percpu+0x1e/0x50
[ 4134.743008] [<ffffffff810c4ff4>] handle_irq_event+0x34/0x60
[ 4134.743008] [<ffffffff810c8217>] handle_edge_irq+0x87/0x140
[ 4134.743008] [<ffffffff8101e486>] handle_irq+0xa6/0x130
[ 4134.743008] [<ffffffff8101dafe>] do_IRQ+0x5e/0x120
[ 4134.743008] [<ffffffff81a90c09>] common_interrupt+0x89/0x89
[ 4134.743008] <EOI> [ 4134.743008] [<ffffffff81a8fb29>] ? _raw_spin_unlock_irq+0x29/0x40
[ 4134.743008] [<ffffffff8114454f>] perf_install_in_context+0x7f/0x160
[ 4134.743008] [<ffffffff8114b790>] ? __perf_event_enable+0x140/0x140
[ 4134.743008] [<ffffffff8114e8b2>] SYSC_perf_event_open+0x512/0xf20
[ 4134.743008] [<ffffffff81151df9>] SyS_perf_event_open+0x9/0x10
[ 4134.743008] [<ffffffff81a9026a>] entry_SYSCALL_64_fastpath+0x18/0xad
[ 4212.748006] INFO: rcu_sched self-detected stall on CPU[ 4212.749020] INFO: rcu_sched detected stalls on CPUs/tasks:
[ 4212.749023] 0-...: (103687 ticks this GP) idle=699/140000000000001/0 softirq=84552/84553 fqs=25939
[ 4212.749024]
[ 4212.749026] (detected by 1, t=104007 jiffies, g=42991, c=42990, q=2440)
[ 4212.749027] Task dump for CPU 0:
[ 4212.749028] perf R
[ 4212.749028] running task 13936 5195 3415 0x00000008
ffffc90005ed7d30
[ 4212.749034] ffffffff81095268 ffff8801b73d9040 00000000001d9040 ffff8801a830ead0
[ 4212.749037] 00000000000000eb ffffffff8114454f ffff8801a830ead0 ffff8801b2918400
[ 4212.749039] ffff8801b2918400 ffff8801afa2e000 ffff8801b2918408Call Trace:
[ 4212.749046] [<ffffffff81095268>] ? sched_clock_local+0x18/0x80
[ 4212.749049] [<ffffffff8114454f>] ? perf_install_in_context+0x7f/0x160
[ 4212.749052] [<ffffffff81a8fb29>] ? _raw_spin_unlock_irq+0x29/0x40
[ 4212.749053] [<ffffffff8114454f>] ? perf_install_in_context+0x7f/0x160
[ 4212.749055] [<ffffffff8114b790>] ? __perf_event_enable+0x140/0x140
[ 4212.749056] [<ffffffff8114e8b2>] ? SYSC_perf_event_open+0x512/0xf20
[ 4212.749058] [<ffffffff81151df9>] ? SyS_perf_event_open+0x9/0x10
[ 4212.749059] [<ffffffff81a9026a>] ? entry_SYSCALL_64_fastpath+0x18/0xad
[ 4212.748007] 0-...: (103687 ticks this GP) idle=699/140000000000001/0 softirq=84552/84553 fqs=25967
[ 4212.748007] (t=104129 jiffies g=42991 c=42990 q=2440)
[ 4212.748007] Task dump for CPU 0:
[ 4212.748007] perf R running task 13936 5195 3415 0x00000008
[ 4212.748007] ffff8801b7203cf8 ffffffff81091cc7 0000000000000000 0000000000000000
[ 4212.748007] 0000000000000086 ffff8801b7203d10 ffffffff81094db4 ffffffff82062180
[ 4212.748007] ffff8801b7203d40 ffffffff81156f72 ffff8801b73d92c0 ffffffff82062180
[ 4212.748007] Call Trace:
[ 4212.748007] <IRQ> [ 4212.748007] [<ffffffff81091cc7>] sched_show_task+0x117/0x1c0
[ 4212.748007] [<ffffffff81094db4>] dump_cpu_task+0x34/0x40
[ 4212.748007] [<ffffffff81156f72>] rcu_dump_cpu_stacks+0x88/0xc4
[ 4212.748007] [<ffffffff810d25c7>] rcu_check_callbacks+0x8a7/0xa00
[ 4212.748007] [<ffffffff810aae4d>] ? trace_hardirqs_off+0xd/0x10
[ 4212.748007] [<ffffffff81066860>] ? raise_softirq+0x110/0x180
[ 4212.748007] [<ffffffff810e8dc0>] ? tick_sched_do_timer+0x30/0x30
[ 4212.748007] [<ffffffff810d7eca>] update_process_times+0x2a/0x50
[ 4212.748007] [<ffffffff810e8651>] tick_sched_handle.isra.15+0x31/0x40
[ 4212.748007] [<ffffffff810e8df8>] tick_sched_timer+0x38/0x70
[ 4212.748007] [<ffffffff810d8f0f>] __hrtimer_run_queues+0xef/0x510
[ 4212.748007] [<ffffffff810d96f2>] hrtimer_interrupt+0xb2/0x1d0
[ 4212.748007] [<ffffffff8104b171>] hpet_interrupt_handler+0x11/0x30
[ 4212.748007] [<ffffffff810c4c77>] __handle_irq_event_percpu+0x37/0x330
[ 4212.748007] [<ffffffff810c4f8e>] handle_irq_event_percpu+0x1e/0x50
[ 4212.748007] [<ffffffff810c4ff4>] handle_irq_event+0x34/0x60
[ 4212.748007] [<ffffffff810c8217>] handle_edge_irq+0x87/0x140
[ 4212.748007] [<ffffffff8101e486>] handle_irq+0xa6/0x130
[ 4212.748007] [<ffffffff8101dafe>] do_IRQ+0x5e/0x120
[ 4212.748007] [<ffffffff81a90c09>] common_interrupt+0x89/0x89
[ 4212.748007] <EOI> [ 4212.748007] [<ffffffff81a8fb29>] ? _raw_spin_unlock_irq+0x29/0x40
[ 4212.748007] [<ffffffff8114454f>] perf_install_in_context+0x7f/0x160
[ 4212.748007] [<ffffffff8114b790>] ? __perf_event_enable+0x140/0x140
[ 4212.748007] [<ffffffff8114e8b2>] SYSC_perf_event_open+0x512/0xf20
[ 4212.748007] [<ffffffff81151df9>] SyS_perf_event_open+0x9/0x10
[ 4212.748007] [<ffffffff81a9026a>] entry_SYSCALL_64_fastpath+0x18/0xad

Dumping the blocked task state:

[ 4314.359550] sysrq: SysRq : Show Blocked State
[ 4314.360006] task PC stack pid father
[ 4314.360006] jbd2/sda1-8 D13728 1370 2 0x00000000
[ 4314.360006] ffff8801b75d8518 ffff8801b5da8000 ffff8801b75d8500 ffff8801b3e3e7c0
[ 4314.360006] ffff8801b3e3e200 ffffc9000108fa40 ffffffff81a8922c ffff8801b3e3e200
[ 4314.360006] ffff8801b3e3e200 ffff8801b75d8518 0000b43c001d9040 ffff8801b3e3e200
[ 4314.360006] Call Trace:
[ 4314.360006] [<ffffffff81a8922c>] ? __schedule+0x2cc/0xa90
[ 4314.360006] [<ffffffff81a8a1b0>] ? bit_wait+0x50/0x50
[ 4314.360006] [<ffffffff81a89a28>] schedule+0x38/0x90
[ 4314.360006] [<ffffffff81a8e687>] schedule_timeout+0x2f7/0x600
[ 4314.360006] [<ffffffff8104b27a>] ? read_hpet+0xea/0x100
[ 4314.360006] [<ffffffff810adbfd>] ? trace_hardirqs_on+0xd/0x10
[ 4314.360006] [<ffffffff810df841>] ? ktime_get+0x91/0x110
[ 4314.360006] [<ffffffff8111f06a>] ? __delayacct_blkio_start+0x1a/0x30
[ 4314.360006] [<ffffffff81a8a1b0>] ? bit_wait+0x50/0x50
[ 4314.360006] [<ffffffff81a88ef1>] io_schedule_timeout+0xa1/0x110
[ 4314.360006] [<ffffffff81a8a1c6>] bit_wait_io+0x16/0x50
[ 4314.360006] [<ffffffff81a89e0f>] __wait_on_bit+0x5f/0x90
[ 4314.360006] [<ffffffff81a8a1b0>] ? bit_wait+0x50/0x50
[ 4314.360006] [<ffffffff81a89f6d>] out_of_line_wait_on_bit+0x6d/0x80
[ 4314.360006] [<ffffffff810a7780>] ? autoremove_wake_function+0x30/0x30
[ 4314.360006] [<ffffffff811f6330>] __wait_on_buffer+0x40/0x50
[ 4314.360006] [<ffffffff812a0f6c>] jbd2_journal_commit_transaction+0x193c/0x2180
[ 4314.360006] [<ffffffff81095268>] ? sched_clock_local+0x18/0x80
[ 4314.360006] [<ffffffff81a8fae1>] ? _raw_spin_unlock_irqrestore+0x31/0x50
[ 4314.360006] [<ffffffff810adbfd>] ? trace_hardirqs_on+0xd/0x10
[ 4314.360006] [<ffffffff812a5cb0>] kjournald2+0xc0/0x270
[ 4314.360006] [<ffffffff810a7750>] ? prepare_to_wait_event+0x110/0x110
[ 4314.360006] [<ffffffff812a5bf0>] ? commit_timeout+0x10/0x10
[ 4314.360006] [<ffffffff8108306e>] kthread+0xee/0x110
[ 4314.360006] [<ffffffff81082f80>] ? kthread_park+0x60/0x60
[ 4314.360006] [<ffffffff81a904c7>] ret_from_fork+0x27/0x40
[ 4314.360006] irqbalance D13560 2290 1 0x00000000
[ 4314.360006] ffff8801b75d8518 ffff8801b5d81880 ffff8801b75d8500 ffff8801af849e40
[ 4314.360006] ffff8801af849880 ffffc90003667c88 ffffffff81a8922c 0000000000000006
[ 4314.360006] 00000000ffffffff ffff8801b75d8518 0000d33e810ad9d1 ffff8801af849880
[ 4314.360006] Call Trace:
[ 4314.360006] [<ffffffff81a8922c>] ? __schedule+0x2cc/0xa90
[ 4314.360006] [<ffffffff81a89a28>] schedule+0x38/0x90
[ 4314.360006] [<ffffffff81a89d00>] schedule_preempt_disabled+0x10/0x20
[ 4314.360006] [<ffffffff81a8b3d3>] mutex_lock_nested+0x173/0x3a0
[ 4314.360006] [<ffffffff815830ad>] ? online_show+0x1d/0x60
[ 4314.360006] [<ffffffff815830ad>] ? online_show+0x1d/0x60
[ 4314.360006] [<ffffffff815830ad>] online_show+0x1d/0x60
[ 4314.360006] [<ffffffff815834cb>] dev_attr_show+0x1b/0x50
[ 4314.360006] [<ffffffff8124220c>] ? sysfs_file_ops+0x3c/0x60
[ 4314.360006] [<ffffffff81242533>] sysfs_kf_seq_show+0xc3/0x1a0
[ 4314.360006] [<ffffffff81240b81>] kernfs_seq_show+0x21/0x30
[ 4314.360006] [<ffffffff811e590f>] seq_read+0xff/0x3b0
[ 4314.360006] [<ffffffff81241566>] kernfs_fop_read+0x126/0x1a0
[ 4314.360006] [<ffffffff811bc343>] __vfs_read+0x23/0x110
[ 4314.360006] [<ffffffff8132df6b>] ? security_file_permission+0x9b/0xc0
[ 4314.360006] [<ffffffff811bc9f4>] ? rw_verify_area+0x44/0xb0
[ 4314.360006] [<ffffffff811bcaea>] vfs_read+0x8a/0x140
[ 4314.360006] [<ffffffff811bdf04>] SyS_read+0x44/0xa0
[ 4314.360006] [<ffffffff81a9026a>] entry_SYSCALL_64_fastpath+0x18/0xad
[ 4314.360006] randomhotplug.s D13376 3371 3370 0x00000000
[ 4314.360006] ffff8801b75d8518 ffff8801b3e16200 ffff8801b75d8500 ffff8801b29d4f40
[ 4314.360006] ffff8801b29d4980 ffffc90004ee7c80 ffffffff81a8922c ffffc90004ee7c58
[ 4314.360006] 0000000000000246 ffff8801b75d8518 0000248281a8be7e ffff8801b29d4980
[ 4314.360006] Call Trace:
[ 4314.360006] [<ffffffff81a8922c>] ? __schedule+0x2cc/0xa90
[ 4314.360006] [<ffffffff81a89a28>] schedule+0x38/0x90
[ 4314.360006] [<ffffffff81060eef>] cpu_hotplug_begin+0xaf/0xc0
[ 4314.360006] [<ffffffff81060e40>] ? __cpuhp_remove_state+0x130/0x130
[ 4314.360006] [<ffffffff810a7750>] ? prepare_to_wait_event+0x110/0x110
[ 4314.360006] [<ffffffff81060fcd>] _cpu_up+0x2d/0xc0
[ 4314.360006] [<ffffffff810610bf>] do_cpu_up+0x5f/0x80
[ 4314.360006] [<ffffffff810610ee>] cpu_up+0xe/0x10
[ 4314.360006] [<ffffffff8158a177>] cpu_subsys_online+0x37/0x80
[ 4314.360006] [<ffffffff815852cc>] device_online+0x5c/0x80
[ 4314.360006] [<ffffffff8158535a>] online_store+0x6a/0x70
[ 4314.360006] [<ffffffff81582aa3>] dev_attr_store+0x13/0x20
[ 4314.360006] [<ffffffff8124226f>] sysfs_kf_write+0x3f/0x50
[ 4314.360006] [<ffffffff81241bbf>] kernfs_fop_write+0x13f/0x1d0
[ 4314.360006] [<ffffffff811bbde3>] __vfs_write+0x23/0x120
[ 4314.360006] [<ffffffff810ccda7>] ? rcu_read_lock_sched_held+0x87/0x90
[ 4314.360006] [<ffffffff810cd07a>] ? rcu_sync_lockdep_assert+0x2a/0x50
[ 4314.360006] [<ffffffff811bfe38>] ? __sb_start_write+0x148/0x1f0
[ 4314.360006] [<ffffffff811bcd1f>] ? vfs_write+0x17f/0x1b0
[ 4314.360006] [<ffffffff811bcc50>] vfs_write+0xb0/0x1b0
[ 4314.360006] [<ffffffff811bdfa4>] SyS_write+0x44/0xa0
[ 4314.360006] [<ffffffff81a9026a>] entry_SYSCALL_64_fastpath+0x18/0xad

... and on arm64:

[ 435.030575] task PC stack pid father
[ 435.036581] randomhotplug.s D 0 2264 2263 0x00000000
[ 435.042060] Call trace:
[ 435.044507] [<ffff200008088fe4>] __switch_to+0x15c/0x220
[ 435.049817] [<ffff2000096d0910>] __schedule+0x480/0x10f8
[ 435.055118] [<ffff2000096d165c>] schedule+0xd4/0x260
[ 435.060078] [<ffff20000810f5ec>] cpu_hotplug_begin+0x134/0x148
[ 435.065900] [<ffff2000096cdaa8>] _cpu_down+0xb0/0x358
[ 435.070941] [<ffff20000810f644>] do_cpu_down+0x44/0x70
[ 435.076068] [<ffff20000810f680>] cpu_down+0x10/0x18
[ 435.080942] [<ffff200008c92438>] cpu_subsys_offline+0x40/0x58
[ 435.086677] [<ffff200008c86b60>] device_offline+0x140/0x1c8
[ 435.092237] [<ffff200008c86dec>] online_store+0x8c/0xe8
[ 435.097458] [<ffff200008c80a48>] dev_attr_store+0x38/0x70
[ 435.102850] [<ffff20000850d248>] sysfs_kf_write+0x108/0x190
[ 435.108411] [<ffff20000850b348>] kernfs_fop_write+0x1c8/0x3c8
[ 435.114147] [<ffff2000083dce10>] __vfs_write+0xc8/0x3c8
[ 435.119360] [<ffff2000083df224>] vfs_write+0x11c/0x428
[ 435.124487] [<ffff2000083e28ac>] SyS_write+0xdc/0x1a8
[ 435.129528] [<ffff200008083ef0>] el0_svc_naked+0x24/0x28

... and again on arm64:

[ 898.370984] htop D 0 16851 15240 0x00000000
[ 898.376459] Call trace:
[ 898.378895] [<ffff200008088fe4>] __switch_to+0x15c/0x220
[ 898.384195] [<ffff2000096d0910>] __schedule+0x480/0x10f8
[ 898.389496] [<ffff2000096d165c>] schedule+0xd4/0x260
[ 898.394450] [<ffff2000096d227c>] schedule_preempt_disabled+0x74/0x110
[ 898.400879] [<ffff2000096d4390>] __mutex_lock_killable_slowpath+0x270/0x670
[ 898.407828] [<ffff2000096d480c>] mutex_lock_killable+0x7c/0x98
[ 898.413649] [<ffff2000084e7b14>] do_io_accounting+0x164/0x660
[ 898.419383] [<ffff2000084e8028>] proc_tgid_io_accounting+0x18/0x20
[ 898.425551] [<ffff2000084e64b4>] proc_single_show+0xcc/0x148
[ 898.431199] [<ffff20000843f3dc>] seq_read+0x26c/0xdb0
[ 898.436238] [<ffff2000083dca58>] __vfs_read+0xc8/0x3b8
[ 898.441364] [<ffff2000083def00>] vfs_read+0xc8/0x2d0
[ 898.446317] [<ffff2000083e2704>] SyS_read+0xdc/0x1a8
[ 898.451269] [<ffff200008083ef0>] el0_svc_naked+0x24/0x28
[ 898.456568] perf R running task 0 17019 10076 0x0000000a
[ 898.463609] Call trace:
[ 898.466046] [<ffff2000080902b8>] dump_backtrace+0x0/0x3d0
[ 898.471433] [<ffff20000809069c>] show_stack+0x14/0x20
[ 898.476476] [<ffff200008173550>] sched_show_task+0x188/0x248
[ 898.482123] [<ffff200008173704>] show_state_filter+0xf4/0x168
[ 898.487858] [<ffff200008bc8418>] sysrq_handle_showstate+0x10/0x20
[ 898.493940] [<ffff200008bc9760>] __handle_sysrq+0x218/0x318
[ 898.499500] [<ffff200008bc9888>] handle_sysrq+0x28/0x30
[ 898.504718] [<ffff200008c1fb78>] pl011_fifo_to_tty+0x110/0x498
[ 898.510539] [<ffff200008c21fb0>] pl011_int+0x740/0xbe8
[ 898.515666] [<ffff2000081c9004>] __handle_irq_event_percpu+0x154/0x260
[ 898.522182] [<ffff2000081c917c>] handle_irq_event_percpu+0x6c/0x110
[ 898.528436] [<ffff2000081c92cc>] handle_irq_event+0xac/0x148
[ 898.534086] [<ffff2000081d2780>] handle_fasteoi_irq+0x218/0x5e8
[ 898.539994] [<ffff2000081c6fa8>] generic_handle_irq+0x48/0x68
[ 898.545728] [<ffff2000081c7ca4>] __handle_domain_irq+0x9c/0x158
[ 898.551636] [<ffff200008081b20>] gic_handle_irq+0x58/0xb0
[ 898.557023] Exception stack(0xffff80034e8c3a90 to 0xffff80034e8c3bc0)
[ 898.563452] 3a80: ffff80034e8c001c ffff2000082a66c0
[ 898.571270] 3aa0: ffff80034e8c3d10 0000000000000001 0000000000000007 0000000000000000
[ 898.579088] 3ac0: 1ffff00069d18003 ffff100069d18784 0000000041b58ab3 ffff80034e8c0000
[ 898.586905] 3ae0: 0000000000000880 0000000000000000 ffff8003fff788cc ffff80035476a780
[ 898.594723] 3b00: 0000000002da8fa8 0000000000000000 0000000000000000 0000000000000000
[ 898.602541] 3b20: 0000000000000000 1ffff00069d18784 ffff80034e8c0000 ffff80034e8c0000
[ 898.610359] 3b40: 0000000000000001 0000000000000006 ffff80034a27c000 00000000fffffffa
[ 898.618176] 3b60: ffff2000082a6000 ffff10006a0021c3 ffff80034e8c3d10 ffff80034e8c3bc0
[ 898.625994] 3b80: ffff2000082a07cc ffff80034e8c3bc0 ffff20000822586c 0000000020000145
[ 898.633811] 3ba0: 0000000000000000 0000000000000000 0001000000000000 ffff800350010d88
[ 898.641628] [<ffff2000080837b0>] el1_irq+0xb0/0x124
[ 898.646496] [<ffff20000822586c>] smp_call_function_single+0xe4/0x3b8
[ 898.652839] [<ffff2000082a07cc>] perf_install_in_context+0x15c/0x268
[ 898.659187] [<ffff2000082c1558>] SyS_perf_event_open+0x1138/0x1908
[ 898.665357] [<ffff200008083ef0>] el0_svc_naked+0x24/0x28
[ 898.670657] perf S 0 17020 17019 0x00000000
[ 898.676133] Call trace:
[ 898.678569] [<ffff200008088fe4>] __switch_to+0x15c/0x220
[ 898.683870] [<ffff2000096d0910>] __schedule+0x480/0x10f8
[ 898.689170] [<ffff2000096d165c>] schedule+0xd4/0x260
[ 898.694123] [<ffff2000083f4a14>] pipe_wait+0xec/0x180
[ 898.699163] [<ffff2000083f5d94>] pipe_read+0x404/0x750
[ 898.704289] [<ffff2000083dcb9c>] __vfs_read+0x20c/0x3b8
[ 898.709501] [<ffff2000083def00>] vfs_read+0xc8/0x2d0
[ 898.714454] [<ffff2000083e2704>] SyS_read+0xdc/0x1a8
[ 898.719407] [<ffff200008083ef0>] el0_svc_naked+0x24/0x28

Thanks,
Mark.