Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 16 Jan 2020 09:40:04 -0800
From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     Qian Cai <cai@lca.pw>
Cc:     Marco Elver <elver@google.com>,
        Alexander Potapenko <glider@google.com>,
        Andrey Konovalov <andreyknvl@google.com>,
        Dmitriy Vyukov <dvyukov@google.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>
Subject: Re: [PATCH -rcu] kcsan: Make KCSAN compatible with lockdep
Message-ID: <20200116174004.GU2935@paulmck-ThinkPad-P72>
Reply-To: paulmck@kernel.org
References: <20200114124919.11891-1-elver@google.com>
 <CAG_fn=X1rFGd1gfML3D5=uiLKTmMbPUm0UD6D0+bg+_hJtQMqA@mail.gmail.com>
 <CANpmjNP6+NTr7_rkNPVDbczst5vutW2K6FXXqkqFg6GGbQC31Q@mail.gmail.com>
 <20200115163754.GA2935@paulmck-ThinkPad-P72>
 <B2717BA1-B964-4B0A-BE4F-5B244087B9E5@lca.pw>
 <D8636F45-621D-4A9F-A7A7-3399450DDAF0@lca.pw>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <D8636F45-621D-4A9F-A7A7-3399450DDAF0@lca.pw>
User-Agent: Mutt/1.9.4 (2018-02-28)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Jan 15, 2020 at 11:37:47PM -0500, Qian Cai wrote:
> 
> > On Jan 15, 2020, at 10:39 PM, Qian Cai <cai@lca.pw> wrote:
> >> On Jan 15, 2020, at 11:37 AM, Paul E. McKenney <paulmck@kernel.org> wrote:
> >> On Wed, Jan 15, 2020 at 05:26:55PM +0100, Marco Elver wrote:
> >>> On Tue, 14 Jan 2020 at 18:24, Alexander Potapenko <glider@google.com> wrote:
> >>>> 
> >>>>> --- a/kernel/kcsan/core.c
> >>>>> +++ b/kernel/kcsan/core.c
> >>>>> @@ -337,7 +337,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
> >>>>>        *      detection point of view) to simply disable preemptions to ensure
> >>>>>        *      as many tasks as possible run on other CPUs.
> >>>>>        */
> >>>>> -       local_irq_save(irq_flags);
> >>>>> +       raw_local_irq_save(irq_flags);
> >>>> 
> >>>> Please reflect the need to use raw_local_irq_save() in the comment.
> >>>> 
> >>>>> 
> >>>>>       watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
> >>>>>       if (watchpoint == NULL) {
> >>>>> @@ -429,7 +429,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
> >>>>> 
> >>>>>       kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS);
> >>>>> out_unlock:
> >>>>> -       local_irq_restore(irq_flags);
> >>>>> +       raw_local_irq_restore(irq_flags);
> >>>> 
> >>>> Ditto
> >>> 
> >>> Done. v2: http://lkml.kernel.org/r/20200115162512.70807-1-elver@google.com
> >> 
> >> Alexander and Qian, could you please let me know if this fixes things
> >> up for you?
> > 
> > The lockdep warning is gone, so feel free to add,
> > 
> > Tested-by: Qian Cai <cai@lca.pw>
> > 
> > for that patch, but the system is still unable to boot due to spam of
> > warnings due to incompatible with debug_pagealloc, debugobjects, so
> > the warning rate limit does not help.
> 
> I set CONFIG_DEBUG_OBJECTS=n to see how further it could go, but
> the kernel is dead after those lines. Unable to boot any further.

How large a system are you running on?  The reason that I ask is that I
have been running it on a 12-CPU system with and without lockdep for some
time.  So perhaps you are running this on a large system (thus indicating
a need for better scalability) or are using an additional Kconfig option?

						Thanx, Paul

> …
> [  111.345991][  T789] Reported by Kernel Concurrency Sanitizer on:
> [  111.373039][  T789] CPU: 44 PID: 789 Comm: systemd-udevd Not tainted 5.5.0-rc6-next-20200115+ #4
> [  111.414596][  T789] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> [  111.459984][  T789] ==================================================================
> [  111.554563][  T777] ==================================================================
> [  111.590304][  T777] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr
> [  111.626392][  T777] 
> [  111.636881][  T777] write to 0xffffffff9a19cde0 of 8 bytes by task 796 on cpu 1:
> [  111.671544][  T777]  __change_page_attr+0xe9c/0x1620
> [  111.695067][  T777]  __change_page_attr_set_clr+0xde/0x4c0
> [  111.722124][  T777]  __set_pages_p+0xcc/0x100
> [  111.742644][  T777]  __kernel_map_pages+0x2e/0xdb
> [  111.765379][  T777]  prep_new_page+0x87/0x1f0
> [  111.785804][  T777]  get_page_from_freelist+0x1583/0x22b0
> [  111.810633][  T777]  __alloc_pages_nodemask+0x1b1/0x450
> [  111.835196][  T777]  alloc_pages_current+0xa6/0x120
> [  111.858619][  T777]  __vmalloc_node_range+0x338/0x480
> [  111.882253][  T777]  __vmalloc_node.constprop.29+0x70/0xb0
> [  111.908550][  T777]  vmalloc+0x69/0x80
> [  111.927150][  T777]  kernel_read_file+0x241/0x2b0
> [  111.950372][  T777]  kernel_read_file_from_fd+0x56/0x90
> [  111.976025][  T777]  __do_sys_finit_module+0xc7/0x190
> [  111.999847][  T777]  __x64_sys_finit_module+0x4c/0x60
> [  112.023326][  T777]  do_syscall_64+0x91/0xb47
> [  112.043903][  T777]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> [  112.070954][  T777] 
> [  112.081261][  T777] read to 0xffffffff9a19cde0 of 8 bytes by task 777 on cpu 16:
> [  112.115510][  T777]  __change_page_attr+0xe81/0x1620
> [  112.138564][  T777]  __change_page_attr_set_clr+0xde/0x4c0
> [  112.164452][  T777]  __set_pages_p+0xcc/0x100
> [  112.185228][  T777]  __kernel_map_pages+0x2e/0xdb
> [  112.207122][  T777]  prep_new_page+0x87/0x1f0
> [  112.227507][  T777]  get_page_from_freelist+0x1583/0x22b0
> [  112.252947][  T777]  __alloc_pages_nodemask+0x1b1/0x450
> [  112.277504][  T777]  alloc_pages_current+0xa6/0x120
> [  112.300450][  T777]  alloc_slab_page+0x3b1/0x540
> [  112.322039][  T777]  allocate_slab+0x70/0x660
> [  112.342387][  T777]  new_slab+0x46/0x70
> [  112.360102][  T777]  ___slab_alloc+0x4ad/0x7d0
> [  112.380944][  T777]  __slab_alloc+0x43/0x70
> [  112.400596][  T777]  kmem_cache_alloc+0x2c3/0x420
> [  112.423674][  T777]  create_object+0x69/0x690
> [  112.447347][  T777]  kmemleak_alloc+0x7d/0xb0
> [  112.469100][  T777]  __kmalloc_track_caller+0x157/0x3c0
> [  112.493548][  T777]  kstrdup+0x3d/0x70
> [  112.510959][  T777]  mod_sysfs_setup+0x5e5/0xb10
> [  112.532234][  T777]  load_module+0x2510/0x2b60
> [  112.552985][  T777]  __do_sys_finit_module+0x14d/0x190
> [  112.577212][  T777]  __x64_sys_finit_module+0x4c/0x60
> [  112.601135][  T777]  do_syscall_64+0x91/0xb47
> [  112.621690][  T777]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> [  112.648566][  T777] 
> [  112.659018][  T777] Reported by Kernel Concurrency Sanitizer on:
> [  112.687603][  T777] CPU: 16 PID: 777 Comm: systemd-udevd Not tainted 5.5.0-rc6-next-20200115+ #4
> [  112.729082][  T777] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018
> [  112.772563][  T777] ==================================================================
> [  112.810304][  T364] ==================================================================
> [  112.848145][  T364] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr
> [  112.884579][  T364] 
> [  112.884586][  T364] read to 0xffffffff9a19cde0 of 8 bytes by task 789 on cpu 12:
> [  112.884595][  T364]  __change_page_attr+0xe81/0x1620
> [  112.884602][  T364]  __change_page_attr_set_clr+0xde/0x4c0
> [  112.884607][  T364]  __set_pages_p+0xcc/0x100
> [  112.884612][  T364]  __kernel_map_pages+0x2e/0xdb
>          [  112.884619][  T364]  prep_new_page+0x87/0x1f0
> [  112.884627][  T364]  get_page_from_freelist+0x1583/0x22b0
> [  112.884633][  T364]  __alloc_pages_nodemask+0x1b1/0x450
> [  112.884640][  T364]  alloc_pages_vma+0x8a/0x2c0
> [  112.884646][  T364]  wp_page_copy+0x100/0x930
> Starting Show Pl[  112.884653][  T364]  do_wp_page+0x107/0x7b0
> [  112.884660][  T364]  __handle_mm_fault+0xce6/0xd40
> [  112.884667][  T364]  handle_mm_fault+0xfc/0x2f0
> [  112.884677][  T364]  do_page_fault+0x263/0x6f9
> ymouth Boot Screen...
> perf: interrupt took too long (7468 > 7338), lowering kernel.perf_event_max_sample_rate to 26700
> perf: interrupt took too long (9463 > 9335), lowering kernel.perf_event_max_sample_rate to 21100
> 
> > 
> > [   28.992752][  T394] Reported by Kernel Concurrency Sanitizer on: 
> > [   28.992752][  T394] CPU: 0 PID: 394 Comm: pgdatinit0 Not tainted 5.5.0-rc6-next-20200115+ #3 
> > [   28.992752][  T394] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
> > [   28.992752][  T394] =============================================================== 
> > [   28.992752][  T394] ================================================================== 
> > [   28.992752][  T394] BUG: KCSAN: data-race in __change_page_attr / __change_page_attr 
> > [   28.992752][  T394]  
> > [   28.992752][  T394] read to 0xffffffffa01a6de0 of 8 bytes by task 395 on cpu 16: 
> > [   28.992752][  T394]  __change_page_attr+0xe81/0x1620 
> > [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0 
> > [   28.992752][  T394]  __set_pages_np+0xcc/0x100 
> > [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb 
> > [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730 
> > [   28.992752][  T394]  __free_pages+0x51/0x90 
> > [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0 
> > [   28.992752][  T394]  deferred_free_range+0x59/0x8f 
> > [   28.992752][  T394]  deferred_init_max21d 
> > [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1 
> > [   28.992752][  T394]  kthread+0x1e0/0x200 
> > [   28.992752][  T394]  ret_from_fork+0x3a/0x50 
> > [   28.992752][  T394]  
> > [   28.992752][  T394] write to 0xffffffffa01a6de0 of 8 bytes by task 394 on cpu 0: 
> > [   28.992752][  T394]  __change_page_attr+0xe9c/0x1620 
> > [   28.992752][  T394]  __change_page_attr_set_clr+0xde/0x4c0 
> > [   28.992752][  T394]  __set_pages_np+0xcc/0x100 
> > [   28.992752][  T394]  __kernel_map_pages+0xd6/0xdb 
> > [   28.992752][  T394]  __free_pages_ok+0x1a8/0x730 
> > [   28.992752][  T394]  __free_pages+0x51/0x90 
> > [   28.992752][  T394]  __free_pages_core+0x1c7/0x2c0 
> > [   28.992752][  T394]  deferred_free_range+0x59/0x8f 
> > [   28.992752][  T394]  deferred_init_maxorder+0x1d6/0x21d 
> > [   28.992752][  T394]  deferred_init_memmap+0x14a/0x1c1 
> > [   28.992752][  T394]  kthread+0x1e0/0x200 
> > [   28.992752][  T394]  ret_from_fork+0x3a/0x50 
> > 
> > 
> > [   93.233621][  T349] Reported by Kernel Concurrency Sanitizer on: 
> > [   93.261902][  T349] CPU: 19 PID: 349 Comm: kworker/19:1 Not tainted 5.5.0-rc6-next-20200115+ #3 
> > [   93.302634][  T349] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
> > [   93.345413][  T349] Workqueue: memcg_kmem_cache memcg_kmem_cache_create_func 
> > [   93.378715][  T349] ================================================================== 
> > [   93.416183][  T616] ================================================================== 
> > [   93.453415][  T616] BUG: KCSAN: data-race in __debug_object_init / fill_pool 
> > [   93.486775][  T616]  
> > [   93.497644][  T616] read to 0xffffffff9ff33b78 of 4 bytes by task 617 on cpu 12: 
> > [   93.534139][  T616]  fill_pool+0x38/0x700 
> > [   93.554913][  T616]  __debug_object_init+0x3f/0x900 
> > [   93.579459][  T616]  debug_object_init+0x39/0x50 
> > [   93.601952][  T616]  __init_work+0x3e/0x50 
> > [   93.620611][  T616]  memcg_kmem_get_cache+0x3c8/0x480 
> > [   93.643619][  T616]  slab_pre_alloc_hook+0x5d/0xa0 
> > [   93.665134][  T616]  __kmalloc_node+0x60/0x300 
> > [   93.685094][  T616]  kvmalloc_node+0x83/0xa0 
> > [   93.704235][  T616]  seq_read+0x57c/0x7a0 
> > [   93.722460][  T616]  proc_reg_read+0x11a/0x160 
> > [   93.743570][  T616]  __vfs_read+0x59/0xa0 
> > [   93.761660][  T616]  vfs_read+0xcf/0x1c0 
> > [   93.779269][  T616]  ksys_read+0x9d/0x130 
> > [   93.797267][  T616]  __x64_sys_read+0x4c/0x60 
> > [   93.817205][  T616]  do_syscall_64+0x91/0xb47 
> > [   93.837590][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
> > [   93.864425][  T616]  
> > [   93.874830][  T616] write to 0xffffffff9ff33b78 of 4 bytes by task 616 on cpu 61: 
> > [   93.908534][  T616]  __debug_object_init+0x6e5/0x900 
> > [   93.931018][  T616]  debug_object_activate+0x1fc/0x350 
> > [   93.954131][  T616]  call_rcu+0x4c/0x4e0 
> > [   93.971959][  T616]  put_object+0x6a/0x90 
> > [   93.989955][  T616]  __delete_object+0xb9/0xf0 
> > [   94.009996][  T616]  delete_object_full+0x2d/0x40 
> > [   94.031812][  T616]  kmemleak_free+0x5f/0x90 
> > [   94.054671][  T616]  slab_free_freelist_hook+0x124/0x1c0 
> > [   94.082027][  T616]  kmem_cache_free+0x10c/0x3a0 
> > [   94.103806][  T616]  vm_area_free+0x31/0x40 
> > [   94.124587][  T616]  remove_vma+0xb0/0xc0 
> > [   94.143484][  T616]  exit_mmap+0x14c/0x220 
> > [   94.163826][  T616]  mmput+0x10e/0x270 
> > [   94.181736][  T616]  flush_old_exec+0x572/0xfe0 
> > [   94.202760][  T616]  load_elf_binary+0x467/0x2180 
> > [   94.224819][  T616]  search_binary_handler+0xd8/0x2b0 
> > [   94.248735][  T616]  __do_execve_file+0xb61/0x1080 
> > [   94.270943][  T616]  __x64_sys_execve+0x5f/0x70 
> > [   94.292254][  T616]  do_syscall_64+0x91/0xb47 
> > [   94.312712][  T616]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
> > 
> > [  103.455945][   C22] Reported by Kernel Concurrency Sanitizer on: 
> > [  103.483032][   C22] CPU: 22 PID: 0 Comm: swapper/22 Not tainted 5.5.0-rc6-next-20200115+ #3 
> > [  103.520563][   C22] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
> > [  103.561771][   C22] ================================================================== 
> > [  103.598005][   C41] ================================================================== 
> > [  103.633820][   C41] BUG: KCSAN: data-race in intel_pstate_update_util / intel_pstate_update_util 
> > [  103.673408][   C41]  
> > [  103.683214][   C41] read to 0xffffffffa9098a58 of 2 bytes by interrupt on cpu 2: 
> > [  103.716645][   C41]  intel_pstate_update_util+0x580/0xb40 
> > [  103.740609][   C41]  cpufreq_update_util+0xb0/0x160 
> > [  103.762611][   C41]  update_blocked_averages+0x585/0x630 
> > [  103.786435][   C41]  run_rebalance_domains+0xd5/0x240 
> > [  103.812821][   C41]  __do_softirq+0xd9/0x57c 
> > [  103.834438][   C41]  irq_exit+0xa2/0xc0 
> > [  103.851773][   C41]  smp_apic_timer_interrupt+0x190/0x480 
> > [  103.876005][   C41]  apic_timer_interrupt+0xf/0x20 
> > [  103.897495][   C41]  cpuidle_enter_state+0x18a/0x9b0 
> > [  103.919324][   C41]  cpuidle_enter+0x69/0xc0 
> > [  103.938405][   C41]  call_cpuidle+0x23/0x40 
> > [  103.957152][   C41]  do_idle+0x248/0x280 
> > [  103.974728][   C41]  cpu_startup_entry+0x1d/0x1f 
> > [  103.995059][   C41]  start_secondary+0x1ad/0x230 
> > [  104.015920][   C41]  secondary_startup_64+0xb6/0xc0 
> > [  104.037376][   C41]  
> > [  104.047144][   C41] write to 0xffffffffa9098a59 of 1 bytes by interrupt on cpu 41: 
> > [  104.081113][   C41]  intel_pstate_update_util+0x4cf/0xb40 
> > [  104.105862][   C41]  cpufreq_update_util+0xb0/0x160 
> > [  104.127759][   C41]  update_load_avg+0x70e/0x800 
> > [  104.148400][   C41]  task_tick_fair+0x5c/0x680 
> > [  104.168325][   C41]  scheduler_tick+0xab/0x120 
> > [  104.188881][   C41]  update_process_times+0x44/0x60 
> > [  104.210811][   C41]  tick_sched_handle+0x4f/0xb0 
> > [  104.231137][   C41]  tick_sched_timer+0x45/0xc0 
> > [  104.251431][   C41]  __hrtimer_run_queues+0x243/0x800 
> > [  104.274362][   C41]  hrtimer_interrupt+0x1d4/0x3e0 
> > [  104.295860][   C41]  smp_apic_timer_interrupt+0x11d/0x480 
> > [  104.325136][   C41]  apic_timer_interrupt+0xf/0x20 
> > [  104.347864][   C41]  __kcsan_check_access+0x1a/0x120 
> > [  104.370100][   C41]  __read_once_size+0x1f/0xe0 
> > [  104.390064][   C41]  smp_call_function_many+0x4b0/0x5d0 
> > [  104.413591][   C41]  on_each_cpu+0x46/0x90 
> > [  104.431954][   C41]  flush_tlb_kernel_range+0x97/0xc0 
> > [  104.454702][   C41]  free_unmap_vmap_area+0xaa/0xe0 
> > [  104.476699][   C41]  remove_vm_area+0xf4/0x100 
> > [  104.496763][   C41]  __vunmap+0x10a/0x460 
> > [  104.514807][   C41]  __vfree+0x33/0x90 
> > [  104.531597][   C41]  vfree+0x47/0x80 
> > [  104.547600][   C41]  n_tty_close+0x56/0x80 
> > [  104.565988][   C41]  tty_ldisc_close+0x76/0xa0 
> > [  104.585912][   C41]  tty_ldisc_kill+0x51/0xa0 
> > [  104.605864][   C41]  tty_ldisc_release+0xf4/0x1a0 
> > [  104.627098][   C41]  tty_release_struct+0x23/0x60 
> > [  104.648268][   C41]  tty_release+0x673/0x9c0 
> > [  104.667517][   C41]  __fput+0x187/0x410 
> > [  104.684357][   C41]  ____fput+0x1e/0x30 
> > [  104.701542][   C41]  task_work_run+0xed/0x140 
> > [  104.721358][   C41]  do_syscall_64+0x803/0xb47 
> > [  104.740872][   C41]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > 
> > [  136.745789][   C34] Reported by Kernel Concurrency Sanitizer on: 
> > [  136.774278][   C34] CPU: 34 PID: 0 Comm: swapper/34 Not tainted 5.5.0-rc6-next-20200115+ #3 
> > [  136.814948][   C34] Hardware name: HP ProLiant XL230a Gen9/ProLiant XL230a Gen9, BIOS U13 01/22/2018 
> > [  136.861974][   C34] ================================================================== 
> > [  136.911354][    T1] ================================================================== 
> > [  136.948491][    T1] BUG: KCSAN: data-race in __debug_object_init / fill_pool 
> > [  136.981645][    T1]  
> > [  136.992045][    T1] read to 0xffffffff9ff33b78 of 4 bytes by task 762 on cpu 25: 
> > [  137.026513][    T1]  fill_pool+0x38/0x700 
> > [  137.045575][    T1]  __debug_object_init+0x3f/0x900 
> > [  137.068826][    T1]  debug_object_activate+0x1fc/0x350 
> > [  137.093102][    T1]  call_rcu+0x4c/0x4e0 
> > [  137.111520][    T1]  __fput+0x23a/0x410 
> > [  137.129618][    T1]  ____fput+0x1e/0x30 
> > [  137.147627][    T1]  task_work_run+0xed/0x140 
> > [  137.168322][    T1]  do_syscall_64+0x803/0xb47 
> > [  137.188572][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
> > [  137.215309][    T1]  
> > [  137.225579][    T1] write to 0xffffffff9ff33b78 of 4 bytes by task 1 on cpu 7: 
> > [  137.259867][    T1]  __debug_object_init+0x6e5/0x900 
> > [  137.283065][    T1]  debug_object_activate+0x1fc/0x350 
> > [  137.306988][    T1]  call_rcu+0x4c/0x4e0 
> > [  137.326804][    T1]  dentry_free+0x70/0xe0 
> > [  137.347208][    T1]  __dentry_kill+0x1db/0x300 
> > [  137.369468][    T1]  shrink_dentry_list+0x153/0x2e0 
> > [  137.393437][    T1]  shrink_dcache_parent+0x1ee/0x320 
> > [  137.417174][    T1]  d_invalidate+0x80/0x130 
> > [  137.437280][    T1]  proc_flush_task+0x14c/0x2b0 
> > [  137.459263][    T1]  release_task.part.21+0x156/0xb50 
> > [  137.483580][    T1]  wait_consider_task+0x17a8/0x1960 
> > [  137.507550][    T1]  do_wait+0x25b/0x560 
> > [  137.526175][    T1]  kernel_waitid+0x194/0x270 
> > [  137.547105][    T1]  __do_sys_waitid+0x18e/0x1e0 
> > [  137.568951][    T1]  __x64_sys_waitid+0x70/0x90 
> > [  137.590291][    T1]  do_syscall_64+0x91/0xb47 
> > [  137.610681][    T1]  entry_SYSCALL_64_after_hwframe+0x49/0xbe 
>