Re: [PATCH -next] cgroup: Fix AA deadlock caused by cgroup_bpf_release

[chenridong <chenridong@xxxxxxxxxx>]

On 2024/7/9 21:42, chenridong wrote:
> On 2024/6/10 10:47, Roman Gushchin wrote:
> > Hi Chen!
> >
> > Was this problem found in the real life? Do you have a LOCKDEP splash 
> > available?
> Sorry for the late email response.
> Yes, it was. The issue occurred after a long period of stress testing, 
> with a very low probability.
> > > On Jun 7, 2024, at 4:09 AM, Chen Ridong <chenridong@xxxxxxxxxx> wrote:
> > >
> > > We found an AA deadlock problem as shown belowed:
> > >
> > > cgroup_destroy_wq        TaskB                WatchDog            
> > > system_wq
> > >
> > > ...
> > > css_killed_work_fn:
> > > P(cgroup_mutex)
> > > ...
> > >                                 ...
> > >                                 __lockup_detector_reconfigure:
> > >                                 P(cpu_hotplug_lock.read)
> > >                                 ...
> > >                 ...
> > >                 percpu_down_write:
> > >                 P(cpu_hotplug_lock.write)
> > >                                                 ...
> > >                                                 cgroup_bpf_release:
> > >                                                 P(cgroup_mutex)
> > >                                 smp_call_on_cpu:
> > >                                 Wait system_wq
> > >
> > > cpuset_css_offline:
> > > P(cpu_hotplug_lock.read)
> > >
> > > WatchDog is waiting for system_wq, who is waiting for cgroup_mutex, to
> > > finish the jobs, but the owner of the cgroup_mutex is waiting for
> > > cpu_hotplug_lock. This problem caused by commit 4bfc0bb2c60e ("bpf:
> > > decouple the lifetime of cgroup_bpf from cgroup itself")
> > > puts cgroup_bpf release work into system_wq. As cgroup_bpf is a 
> > > member of
> > > cgroup, it is reasonable to put cgroup bpf release work into
> > > cgroup_destroy_wq, which is only used for cgroup's release work, and the
> > > preblem is solved.
> >
> > I need to think more on this, but at first glance the fix looks a bit 
> > confusing. cgroup_bpf_release() looks quite innocent, it only takes a 
> > cgroup_mutex. It’s not obvious why it’s not ok and requires a 
> > dedicated work queue. What exactly is achieved by placing it back on 
> > the dedicated cgroup destroy queue?
> >
> > I’m not trying to say your fix won’t work, but it looks like it might 
> > cover a more serious problem.
>
> The issue lies in the fact that different tasks require the cgroup_mutex 
> and cpu_hotplug_lock locks, eventually forming a deadlock. Placing 
> cgroup bpf release work on cgroup destroy queue can break loop.
The max_active of system_wq is WQ_DFL_ACTIVE(256). If all active works 
are cgroup bpf release works, it will block smp_call_on_cpu work which 
enque after cgroup bpf releases. So smp_call_on_cpu holding 
cpu_hotplug_lock will wait for completion, but it can never get a 
completion because cgroup bpf release works can not get cgroup_mutex and 
will never finish.
However, Placing the cgroup bpf release works on cgroup destroy will 
never block smp_call_on_cpu work, which means loop is broken. Thus, it 
can solve the problem.

> The issue can be reproduced by the following method(with qemu -smp 4).
> 1.mkdir and rmdir cgroup repeatly
> #!/bin/bash
> timestamp=$(date +%s)
> for ((i=0; i<2000; i++))
> do
>      mkdir /sys/fs/cgroup/cpuset/test$timestamp_$i &
>      mkdir /sys/fs/cgroup/memory/test$timestamp_$i &
> done
>
> for ((i=0; i<2000; i++))
> do
>      rmdir /sys/fs/cgroup/cpuset/test$timestamp_$i &
>      rmdir /sys/fs/cgroup/memory/test$timestamp_$i &
> done
> 2. set cpu on and off repeatly
> #!/bin/bash
>
> while true
> do
> echo 1 > /sys/devices/system/cpu/cpu2/online
> echo 0 > /sys/devices/system/cpu/cpu2/online
> done
> 3.set watchdog_thresh repeatly
> #!/bin/bash
>
> while true
> do
> echo 12 > /proc/sys/kernel/watchdog_thresh
> echo 11 > /proc/sys/kernel/watchdog_thresh
> echo 10 > /proc/sys/kernel/watchdog_thresh
> done
>
> 4.add mdelay to reproduce(it is hard to reproduce if we do not have this 
> helper)
> #include "../cgroup/cgroup-internal.h"
> +#include <linux/delay.h>
>
>   DEFINE_STATIC_KEY_ARRAY_FALSE(cgroup_bpf_enabled_key, 
> MAX_CGROUP_BPF_ATTACH_TYPE);
>   EXPORT_SYMBOL(cgroup_bpf_enabled_key);
> @@ -281,7 +282,7 @@ static void cgroup_bpf_release(struct work_struct 
> *work)
>          struct bpf_cgroup_storage *storage, *stmp;
>
>          unsigned int atype;
> -
> +       mdelay(50);
>          cgroup_lock();
>
>          for (atype = 0; atype < ARRAY_SIZE(cgrp->bpf.progs); atype++) {
> diff --git a/kernel/smp.c b/kernel/smp.c
> index f085ebcdf9e7..77325566ea69 100644
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -25,6 +25,7 @@
>   #include <linux/nmi.h>
>   #include <linux/sched/debug.h>
>   #include <linux/jump_label.h>
> +#include <linux/delay.h>
>
>   #include <trace/events/ipi.h>
>   #define CREATE_TRACE_POINTS
> @@ -1113,7 +1114,7 @@ int smp_call_on_cpu(unsigned int cpu, int 
> (*func)(void *), void *par, bool phys)
>          };
>
>          INIT_WORK_ONSTACK(&sscs.work, smp_call_on_cpu_callback);
> -
> +       mdelay(10);
>          if (cpu >= nr_cpu_ids || !cpu_online(cpu))
>                  return -ENXIO;
>
> 5.Before 616db8779b1e ("workqueue: Automatically mark CPU-hogging work 
> items CPU_INTENSIVE"), the issue can be reproduced with just the four 
> steps mentioned above.
> After 616db8779b1e ("workqueue: Automatically mark CPU-hogging work 
> items CPU_INTENSIVE") ,cpu_intensive_thresh_us is needed to set as below:
> #echo 100000 > /sys/module/workqueue/parameters/cpu_intensive_thresh_us
>
>
>
> LOCKDEP splash for 6.6:
>
>
> [  955.350702] INFO: task kworker/0:0:8 blocked for more than 327 seconds.
> [  955.357885]       Tainted: G          I 
> 6.6.0-10483-g37a510c04997-dirty #253
> [  955.358344] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
> disables this message.
> [  955.359987] task:kworker/0:0     state:D stack:13920 pid:8     ppid:2 
>       flags:0x00004000
> [  955.362182] Workqueue: events cgroup_bpf_release
> [  955.363867] Call Trace:
> [  955.364588]  <TASK>
> [  955.365156]  __schedule+0x5a2/0x2050
> [  955.366576]  ? find_held_lock+0x33/0x100
> [  955.366790]  ? wq_worker_sleeping+0x9e/0xe0
> [  955.366980]  schedule+0x9f/0x180
> [  955.367150]  schedule_preempt_disabled+0x25/0x50
> [  955.367501]  __mutex_lock+0x512/0x740
> [  955.367774]  ? cgroup_bpf_release+0x1e/0x4d0
> [  955.367946]  ? cgroup_bpf_release+0xcf/0x4d0
> [  955.368097]  ? process_scheduled_works+0x161/0x8a0
> [  955.368254]  ? cgroup_bpf_release+0x1e/0x4d0
> [  955.368566]  ? mutex_lock_nested+0x2b/0x40
> [  955.368732]  ? __pfx_delay_tsc+0x10/0x10
> [  955.368901]  mutex_lock_nested+0x2b/0x40
> [  955.369098]  cgroup_bpf_release+0xcf/0x4d0
> [  955.369271]  ? process_scheduled_works+0x161/0x8a0
> [  955.369621]  ? trace_event_raw_event_workqueue_execute_start+0x64/0xd0
> [  955.369852]  ? process_scheduled_works+0x161/0x8a0
> [  955.370043]  process_scheduled_works+0x23a/0x8a0
> [  955.370260]  worker_thread+0x231/0x5b0
> [  955.370569]  ? __pfx_worker_thread+0x10/0x10
> [  955.370735]  kthread+0x14d/0x1c0
> [  955.370890]  ? __pfx_kthread+0x10/0x10
> [  955.371055]  ret_from_fork+0x59/0x70
> [  955.371219]  ? __pfx_kthread+0x10/0x10
> [  955.371519]  ret_from_fork_asm+0x1b/0x30
> [  955.371813]  </TASK>
> [  955.372136] INFO: task kworker/3:1:44 blocked for more than 327 seconds.
> [  955.372632]       Tainted: G          I 
> 6.6.0-10483-g37a510c04997-dirty #253
> [  955.372870] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
> disables this message.
> [  955.373079] task:kworker/3:1     state:D stack:14256 pid:44    ppid:2 
>       flags:0x00004000
> [  955.373500] Workqueue: events cgroup_bpf_release
> [  955.373701] Call Trace:
> [  955.373803]  <TASK>
> [  955.373911]  __schedule+0x5a2/0x2050
> [  955.374055]  ? find_held_lock+0x33/0x100
> [  955.374196]  ? wq_worker_sleeping+0x9e/0xe0
> [  955.374343]  schedule+0x9f/0x180
> [  955.374608]  schedule_preempt_disabled+0x25/0x50
> [  955.374768]  __mutex_lock+0x512/0x740
> [  955.374911]  ? cgroup_bpf_release+0x1e/0x4d0
> [  955.375057]  ? cgroup_bpf_release+0xcf/0x4d0
> [  955.375220]  ? process_scheduled_works+0x161/0x8a0
> [  955.375540]  ? cgroup_bpf_release+0x1e/0x4d0
> [  955.375735]  ? mutex_lock_nested+0x2b/0x40
> [  955.375926]  ? __pfx_delay_tsc+0x10/0x10
> [  955.376076]  mutex_lock_nested+0x2b/0x40
> [  955.376220]  cgroup_bpf_release+0xcf/0x4d0
> [  955.376517]  ? process_scheduled_works+0x161/0x8a0
> [  955.376724]  ? trace_event_raw_event_workqueue_execute_start+0x64/0xd0
> [  955.376982]  ? process_scheduled_works+0x161/0x8a0
> [  955.377192]  process_scheduled_works+0x23a/0x8a0
> [  955.377541]  worker_thread+0x231/0x5b0
> [  955.377742]  ? __pfx_worker_thread+0x10/0x10
> [  955.377931]  kthread+0x14d/0x1c0
> [  955.378076]  ? __pfx_kthread+0x10/0x10
> [  955.378231]  ret_from_fork+0x59/0x70
> [  955.378550]  ? __pfx_kthread+0x10/0x10
> [  955.378709]  ret_from_fork_asm+0x1b/0x30
> [  955.378880]  </TASK>
> [  955.379069] INFO: task systemd-journal:93 blocked for more than 327 
> seconds.
> [  955.379294]       Tainted: G          I 
> 6.6.0-10483-g37a510c04997-dirty #253
> [  955.379759] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
> disables this message.
> [  955.380041] task:systemd-journal state:D stack:12064 pid:93    ppid:1 
>       flags:0x00000002
> [  955.380515] Call Trace:
> [  955.380661]  <TASK>
> [  955.380770]  __schedule+0x5a2/0x2050
> [  955.380938]  ? __lock_acquire.constprop.0+0x24f/0x8d0
> [  955.381115]  ? find_held_lock+0x33/0x100
> [  955.381271]  schedule+0x9f/0x180
> [  955.381579]  schedule_preempt_disabled+0x25/0x50
> [  955.381769]  __mutex_lock+0x512/0x740
> [  955.381922]  ? proc_cgroup_show+0x66/0x3e0
> [  955.382091]  ? mutex_lock_nested+0x2b/0x40
> [  955.382250]  mutex_lock_nested+0x2b/0x40
> [  955.382550]  proc_cgroup_show+0x66/0x3e0
> [  955.382740]  proc_single_show+0x64/0xa0
> [  955.382900]  seq_read_iter+0x155/0x660
> [  955.383045]  ? _copy_to_user+0x34/0x60
> [  955.383186]  ? cp_new_stat+0x14a/0x190
> [  955.383341]  seq_read+0xd5/0x110
> [  955.383650]  vfs_read+0xae/0x1a0
> [  955.383792]  ksys_read+0x81/0x180
> [  955.383940]  __x64_sys_read+0x21/0x30
> [  955.384090]  x64_sys_call+0x2608/0x4630
> [  955.384238]  do_syscall_64+0x44/0xb0
> [  955.384394]  entry_SYSCALL_64_after_hwframe+0x78/0xe2
> [  955.384994] RIP: 0033:0x7fe91e2be81c
> [  955.385530] RSP: 002b:00007ffc1f490df0 EFLAGS: 00000246 ORIG_RAX: 
> 0000000000000000
> [  955.385849] RAX: ffffffffffffffda RBX: 00005609cd32d2f0 RCX: 
> 00007fe91e2be81c
> [  955.386095] RDX: 0000000000000400 RSI: 00005609cd32d520 RDI: 
> 0000000000000019
> [  955.386312] RBP: 00007fe91e3c1600 R08: 0000000000000000 R09: 
> 0000000000000001
> [  955.386815] R10: 0000000000001000 R11: 0000000000000246 R12: 
> 00007fe91d8ecd88
> [  955.387093] R13: 0000000000000d68 R14: 00007fe91e3c0a00 R15: 
> 0000000000000d68
> [  955.387683]  </TASK>
> [  955.387824] INFO: task kworker/3:2:103 blocked for more than 327 
> seconds.
> [  955.388071]       Tainted: G          I 
> 6.6.0-10483-g37a510c04997-dirty #253
> [  955.388313] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
> disables this message.
> [  955.388792] task:kworker/3:2     state:D stack:14688 pid:103   ppid:2 
>       flags:0x00004000
> [  955.389143] Workqueue: events cgroup_bpf_release
> [  955.389332] Call Trace:
> [  955.389610]  <TASK>
> [  955.389725]  __schedule+0x5a2/0x2050
> [  955.389895]  ? find_held_lock+0x33/0x100
> [  955.390046]  ? wq_worker_sleeping+0x9e/0xe0
> [  955.390208]  schedule+0x9f/0x180
> [  955.390478]  schedule_preempt_disabled+0x25/0x50
> [  955.390670]  __mutex_lock+0x512/0x740
> [  955.390816]  ? cgroup_bpf_release+0x1e/0x4d0
> [  955.390989]  ? cgroup_bpf_release+0xcf/0x4d0
> [  955.391161]  ? process_scheduled_works+0x161/0x8a0
> [  955.391487]  ? cgroup_bpf_release+0x1e/0x4d0
> [  955.391677]  ? mutex_lock_nested+0x2b/0x40
> [  955.391825]  ? __pfx_delay_tsc+0x10/0x10
> [  955.391991]  mutex_lock_nested+0x2b/0x40
> [  955.392146]  cgroup_bpf_release+0xcf/0x4d0
> [  955.392307]  ? process_scheduled_works+0x161/0x8a0
> [  955.392728]  ? trace_event_raw_event_workqueue_execute_start+0x64/0xd0
> [  955.392957]  ? process_scheduled_works+0x161/0x8a0
> [  955.393118]  process_scheduled_works+0x23a/0x8a0
> [  955.393276]  worker_thread+0x231/0x5b0
> [  955.393565]  ? __pfx_worker_thread+0x10/0x10
> [  955.393726]  kthread+0x14d/0x1c0
> [  955.393865]  ? __pfx_kthread+0x10/0x10
> [  955.394014]  ret_from_fork+0x59/0x70
> [  955.394150]  ? __pfx_kthread+0x10/0x10
> [  955.394288]  ret_from_fork_asm+0x1b/0x30
> [  955.394619]  </TASK>
> [  955.394737] INFO: task kworker/0:2:154 blocked for more than 327 
> seconds.
> [  955.394947]       Tainted: G          I 
> 6.6.0-10483-g37a510c04997-dirty #253
> [  955.395167] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
> disables this message.
> [  955.395564] task:kworker/0:2     state:D stack:14632 pid:154   ppid:2 
>       flags:0x00004000
> [  955.395896] Workqueue: events cgroup_bpf_release
> [  955.396072] Call Trace:
> [  955.396172]  <TASK>
> [  955.396266]  __schedule+0x5a2/0x2050
> [  955.396576]  ? find_held_lock+0x33/0x100
> [  955.396739]  ? wq_worker_sleeping+0x9e/0xe0
> [  955.396906]  schedule+0x9f/0x180
> [  955.397049]  schedule_preempt_disabled+0x25/0x50
> [  955.397221]  __mutex_lock+0x512/0x740
> [  955.397585]  ? cgroup_bpf_release+0x1e/0x4d0
> [  955.397758]  ? cgroup_bpf_release+0xcf/0x4d0
> [  955.397943]  ? process_scheduled_works+0x161/0x8a0
> [  955.398129]  ? cgroup_bpf_release+0x1e/0x4d0
> [  955.398317]  ? mutex_lock_nested+0x2b/0x40
> [  955.398620]  ? __pfx_delay_tsc+0x10/0x10
> [  955.398781]  mutex_lock_nested+0x2b/0x40
> [  955.398946]  cgroup_bpf_release+0xcf/0x4d0
> [  955.399096]  ? process_scheduled_works+0x161/0x8a0
> [  955.399290]  ? trace_event_raw_event_workqueue_execute_start+0x64/0xd0
> [  955.399729]  ? process_scheduled_works+0x161/0x8a0
> [  955.399927]  process_scheduled_works+0x23a/0x8a0
> [  955.400113]  worker_thread+0x231/0x5b0
> [  955.400274]  ? __pfx_worker_thread+0x10/0x10
> [  955.400618]  kthread+0x14d/0x1c0
> [  955.400768]  ? __pfx_kthread+0x10/0x10
> [  955.400928]  ret_from_fork+0x59/0x70
> [  955.401070]  ? __pfx_kthread+0x10/0x10
> [  955.401216]  ret_from_fork_asm+0x1b/0x30
> [  955.401506]  </TASK>
> [  955.401714] INFO: task cpu_up_down.sh:374 blocked for more than 327 
> seconds.
> [  955.401938]       Tainted: G          I 
> 6.6.0-10483-g37a510c04997-dirty #253
> [  955.402154] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
> disables this message.
> [  955.402502] task:cpu_up_down.sh  state:D stack:13248 pid:374   ppid:1 
>       flags:0x00004002
> [  955.402793] Call Trace:
> [  955.402903]  <TASK>
> [  955.402999]  __schedule+0x5a2/0x2050
> [  955.403148]  schedule+0x9f/0x180
> [  955.403301]  percpu_down_write+0x100/0x230
> [  955.403697]  _cpu_up+0x3a/0x230
> [  955.403872]  cpu_up+0xf0/0x180
> [  955.404010]  cpu_device_up+0x21/0x30
> [  955.404172]  cpu_subsys_online+0x59/0x140
> [  955.404330]  device_online+0xab/0xf0
> [  955.404643]  online_store+0xce/0x100
> [  955.404785]  dev_attr_store+0x1f/0x40
> [  955.404942]  sysfs_kf_write+0x58/0x80
> [  955.405095]  kernfs_fop_write_iter+0x194/0x290
> [  955.405288]  new_sync_write+0xeb/0x160
> [  955.405659]  vfs_write+0x16f/0x1d0
> [  955.405807]  ksys_write+0x81/0x180
> [  955.405947]  __x64_sys_write+0x21/0x30
> [  955.406082]  x64_sys_call+0x2f25/0x4630
> [  955.406220]  do_syscall_64+0x44/0xb0
> [  955.406493]  entry_SYSCALL_64_after_hwframe+0x78/0xe2
> [  955.406725] RIP: 0033:0x7fc5a1d36887
> [  955.406889] RSP: 002b:00007ffc8a71f498 EFLAGS: 00000246 ORIG_RAX: 
> 0000000000000001
> [  955.407183] RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 
> 00007fc5a1d36887
> [  955.407563] RDX: 0000000000000002 RSI: 0000560415993ac0 RDI: 
> 0000000000000001
> [  955.407794] RBP: 0000560415993ac0 R08: 00007fc5a1df3460 R09: 
> 000000007fffffff
> [  955.408011] R10: 0000000000000000 R11: 0000000000000246 R12: 
> 0000000000000002
> [  955.408230] R13: 00007fc5a1e3d780 R14: 00007fc5a1e39600 R15: 
> 00007fc5a1e38a00
> [  955.408631]  </TASK>
> [  955.408746] INFO: task watchdog.sh:375 blocked for more than 327 
> seconds.
> [  955.408963]       Tainted: G          I 
> 6.6.0-10483-g37a510c04997-dirty #253
> [  955.409187] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
> disables this message.
> [  955.409584] task:watchdog.sh     state:D stack:13248 pid:375   ppid:1 
>       flags:0x00004002
> [  955.409895] Call Trace:
> [  955.410039]  <TASK>
> [  955.410146]  __schedule+0x5a2/0x2050
> [  955.410289]  ? __lock_acquire.constprop.0+0x24f/0x8d0
> [  955.410649]  ? msr_event_update+0x20/0xf0
> [  955.410814]  schedule+0x9f/0x180
> [  955.410955]  schedule_timeout+0x146/0x160
> [  955.411100]  ? do_wait_for_common+0x7e/0x260
> [  955.411268]  ? __lock_acquire.constprop.0+0x24f/0x8d0
> [  955.411641]  do_wait_for_common+0x92/0x260
> [  955.411813]  ? __pfx_schedule_timeout+0x10/0x10
> [  955.411994]  ? __pfx_softlockup_start_fn+0x10/0x10
> [  955.412161]  wait_for_completion+0x5e/0x90
> [  955.412327]  smp_call_on_cpu+0x1ba/0x220
> [  955.412655]  ? __pfx_smp_call_on_cpu_callback+0x10/0x10
> [  955.412842]  ? __pfx_softlockup_start_fn+0x10/0x10
> [  955.413032]  __lockup_detector_reconfigure+0x218/0x260
> [  955.413209]  proc_watchdog_thresh+0xcd/0xe0
> [  955.413574]  proc_sys_call_handler+0x1ea/0x390
> [  955.413792]  ? raw_spin_rq_unlock+0x30/0x90
> [  955.413982]  proc_sys_write+0x1b/0x30
> [  955.414151]  new_sync_write+0xeb/0x160
> [  955.414329]  vfs_write+0x16f/0x1d0
> [  955.414684]  ksys_write+0x81/0x180
> [  955.414870]  __x64_sys_write+0x21/0x30
> [  955.415027]  x64_sys_call+0x2f25/0x4630
> [  955.415208]  do_syscall_64+0x44/0xb0
> [  955.415518]  entry_SYSCALL_64_after_hwframe+0x78/0xe2
> [  955.415708] RIP: 0033:0x7f6eb323d887
> [  955.415842] RSP: 002b:00007fffb86753c8 EFLAGS: 00000246 ORIG_RAX: 
> 0000000000000001
> [  955.416084] RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 
> 00007f6eb323d887
> [  955.416288] RDX: 0000000000000003 RSI: 000055b2e5ea4d30 RDI: 
> 0000000000000001
> [  955.416734] RBP: 000055b2e5ea4d30 R08: 00007f6eb32fa460 R09: 
> 000000007fffffff
> [  955.416965] R10: 0000000000000000 R11: 0000000000000246 R12: 
> 0000000000000003
> [  955.417172] R13: 00007f6eb3344780 R14: 00007f6eb3340600 R15: 
> 00007f6eb333fa00
> [  955.417545]  </TASK>
> [  955.417665] INFO: task kworker/0:3:413 blocked for more than 327 
> seconds.
> [  955.417923]       Tainted: G          I 
> 6.6.0-10483-g37a510c04997-dirty #253
> [  955.418175] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
> disables this message.
> [  955.418586] task:kworker/0:3     state:D stack:14648 pid:413   ppid:2 
>       flags:0x00004000
> [  955.418898] Workqueue: events cgroup_bpf_release
> [  955.419087] Call Trace:
> [  955.419240]  <TASK>
> [  955.419529]  __schedule+0x5a2/0x2050
> [  955.419684]  ? find_held_lock+0x33/0x100
> [  955.419837]  ? wq_worker_sleeping+0x9e/0xe0
> [  955.420041]  schedule+0x9f/0x180
> [  955.420206]  schedule_preempt_disabled+0x25/0x50
> [  955.420587]  __mutex_lock+0x512/0x740
> [  955.420751]  ? cgroup_bpf_release+0x1e/0x4d0
> [  955.420968]  ? cgroup_bpf_release+0xcf/0x4d0
> [  955.421166]  ? process_scheduled_works+0x161/0x8a0
> [  955.421333]  ? cgroup_bpf_release+0x1e/0x4d0
> [  955.421678]  ? mutex_lock_nested+0x2b/0x40
> [  955.421840]  ? __pfx_delay_tsc+0x10/0x10
> [  955.421994]  mutex_lock_nested+0x2b/0x40
> [  955.422135]  cgroup_bpf_release+0xcf/0x4d0
> [  955.422281]  ? process_scheduled_works+0x161/0x8a0
> [  955.422652]  ? trace_event_raw_event_workqueue_execute_start+0x64/0xd0
> [  955.422877]  ? process_scheduled_works+0x161/0x8a0
> [  955.423036]  process_scheduled_works+0x23a/0x8a0
> [  955.423210]  worker_thread+0x231/0x5b0
> [  955.423467]  ? __pfx_worker_thread+0x10/0x10
> [  955.423644]  kthread+0x14d/0x1c0
> [  955.423784]  ? __pfx_kthread+0x10/0x10
> [  955.423948]  ret_from_fork+0x59/0x70
> [  955.424118]  ? __pfx_kthread+0x10/0x10
> [  955.424256]  ret_from_fork_asm+0x1b/0x30
> [  955.424581]  </TASK>
> [  955.424729] INFO: task kworker/0:1:3950 blocked for more than 327 
> seconds.
> [  955.424984]       Tainted: G          I 
> 6.6.0-10483-g37a510c04997-dirty #253
> [  955.425213] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
> disables this message.
> [  955.425598] task:kworker/0:1     state:D stack:14840 pid:3950  ppid:2 
>       flags:0x00004000
> [  955.425933] Workqueue: events cgroup_bpf_release
> [  955.426167] Call Trace:
> [  955.426291]  <TASK>
> [  955.426578]  __schedule+0x5a2/0x2050
> [  955.426774]  ? find_held_lock+0x33/0x100
> [  955.426961]  ? wq_worker_sleeping+0x9e/0xe0
> [  955.427170]  schedule+0x9f/0x180
> [  955.427331]  schedule_preempt_disabled+0x25/0x50
> [  955.427664]  __mutex_lock+0x512/0x740
> [  955.427814]  ? cgroup_bpf_release+0x1e/0x4d0
> [  955.427994]  ? cgroup_bpf_release+0xcf/0x4d0
> [  955.428180]  ? process_scheduled_works+0x161/0x8a0
> [  955.428597]  ? cgroup_bpf_release+0x1e/0x4d0
> [  955.428787]  ? mutex_lock_nested+0x2b/0x40
> [  955.428966]  ? __pfx_delay_tsc+0x10/0x10
> [  955.429135]  mutex_lock_nested+0x2b/0x40
> [  955.429283]  cgroup_bpf_release+0xcf/0x4d0
> [  955.429766]  ? process_scheduled_works+0x161/0x8a0
> [  955.429960]  ? trace_event_raw_event_workqueue_execute_start+0x64/0xd0
> [  955.430176]  ? process_scheduled_works+0x161/0x8a0
> [  955.430480]  process_scheduled_works+0x23a/0x8a0
> [  955.430713]  worker_thread+0x231/0x5b0
> [  955.430875]  ? __pfx_worker_thread+0x10/0x10
> [  955.431028]  kthread+0x14d/0x1c0
> [  955.431168]  ? __pfx_kthread+0x10/0x10
> [  955.431333]  ret_from_fork+0x59/0x70
> [  955.431662]  ? __pfx_kthread+0x10/0x10
> [  955.431811]  ret_from_fork_asm+0x1b/0x30
> [  955.431973]  </TASK>
> [  955.432108] INFO: task kworker/0:4:4452 blocked for more than 327 
> seconds.
> [  955.432326]       Tainted: G          I 
> 6.6.0-10483-g37a510c04997-dirty #253
> [  955.432749] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
> disables this message.
> [  955.432979] task:kworker/0:4     state:D stack:14920 pid:4452  ppid:2 
>       flags:0x00004000
> [  955.433278] Workqueue: events cgroup_bpf_release
> [  955.433697] Call Trace:
> [  955.433819]  <TASK>
> [  955.433925]  __schedule+0x5a2/0x2050
> [  955.434068]  ? find_held_lock+0x33/0x100
> [  955.434220]  ? wq_worker_sleeping+0x9e/0xe0
> [  955.434503]  schedule+0x9f/0x180
> [  955.434660]  schedule_preempt_disabled+0x25/0x50
> [  955.434824]  __mutex_lock+0x512/0x740
> [  955.434975]  ? cgroup_bpf_release+0x1e/0x4d0
> [  955.435131]  ? cgroup_bpf_release+0xcf/0x4d0
> [  955.435307]  ? process_scheduled_works+0x161/0x8a0
> [  955.435680]  ? cgroup_bpf_release+0x1e/0x4d0
> [  955.435849]  ? mutex_lock_nested+0x2b/0x40
> [  955.436009]  ? __pfx_delay_tsc+0x10/0x10
> [  955.436149]  mutex_lock_nested+0x2b/0x40
> [  955.436293]  cgroup_bpf_release+0xcf/0x4d0
> [  955.436629]  ? process_scheduled_works+0x161/0x8a0
> [  955.436799]  ? trace_event_raw_event_workqueue_execute_start+0x64/0xd0
> [  955.437009]  ? process_scheduled_works+0x161/0x8a0
> [  955.437162]  process_scheduled_works+0x23a/0x8a0
> [  955.437319]  worker_thread+0x231/0x5b0
> [  955.437634]  ? __pfx_worker_thread+0x10/0x10
> [  955.437806]  kthread+0x14d/0x1c0
> [  955.437961]  ? __pfx_kthread+0x10/0x10
> [  955.438140]  ret_from_fork+0x59/0x70
> [  955.438292]  ? __pfx_kthread+0x10/0x10
> [  955.438641]  ret_from_fork_asm+0x1b/0x30
> [  955.438841]  </TASK>
> [  955.439021] Future hung task reports are suppressed, see sysctl 
> kernel.hung_task_warnings
> [  955.822134]
> [  955.822134] Showing all locks held in the system:
> [  955.822946] 2 locks held by systemd/1:
> [  955.823225]  #0: ffff888100f28440 (&p->lock){....}-{3:3}, at: 
> seq_read_iter+0x69/0x660
> [  955.824341]  #1: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> proc_cgroup_show+0x66/0x3e0
> [  955.825068] 3 locks held by kworker/0:0/8:
> [  955.825221]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.825751]  #1: ffffc9000004be60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.826203]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.826794] 1 lock held by khungtaskd/39:
> [  955.826975]  #0: ffffffff83e24840 (rcu_read_lock){....}-{1:2}, at: 
> debug_show_all_locks+0x46/0x1d0
> [  955.827482] 3 locks held by kworker/3:1/44:
> [  955.827651]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.828073]  #1: ffffc9000018fe60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.828699]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.829076] 2 locks held by systemd-journal/93:
> [  955.829235]  #0: ffff8881046a69b0 (&p->lock){....}-{3:3}, at: 
> seq_read_iter+0x69/0x660
> [  955.829729]  #1: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> proc_cgroup_show+0x66/0x3e0
> [  955.830101] 3 locks held by kworker/3:2/103:
> [  955.830254]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.830785]  #1: ffffc90000d33e60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.831221]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.831737] 3 locks held by kworker/0:2/154:
> [  955.831895]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.832256]  #1: ffffc90000df3e60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.832853]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.833244] 1 lock held by in:imklog/187:
> [  955.833625] 6 locks held by rs:main Q:Reg/188:
> [  955.833847] 7 locks held by cpu_up_down.sh/374:
> [  955.834045]  #0: ffff888103c913e0 (sb_writers#5){....}-{0:0}, at: 
> vfs_write+0xae/0x1d0
> [  955.834892]  #1: ffff8881046fba88 (&of->mutex){....}-{3:3}, at: 
> kernfs_fop_write_iter+0x143/0x290
> [  955.835324]  #2: ffff888101423cf8 (kn->active#57){....}-{0:0}, at: 
> kernfs_fop_write_iter+0x153/0x290
> [  955.835885]  #3: ffffffff8428b168 (device_hotplug_lock){....}-{3:3}, 
> at: lock_device_hotplug_sysfs+0x1d/0x80
> [  955.836329]  #4: ffff888237d2d3a0 (&dev->mutex){....}-{3:3}, at: 
> device_online+0x29/0xf0
> [  955.836813]  #5: ffffffff83cd5068 (cpu_add_remove_lock){....}-{3:3}, 
> at: cpu_up+0x54/0x180
> [  955.837196]  #6: ffffffff83cd4fd0 (cpu_hotplug_lock){....}-{0:0}, at: 
> _cpu_up+0x3a/0x230
> [  955.837753] 3 locks held by watchdog.sh/375:
> [  955.837927]  #0: ffff888103c903e0 (sb_writers#4){....}-{0:0}, at: 
> vfs_write+0xae/0x1d0
> [  955.838250]  #1: ffffffff83e71148 (watchdog_mutex){....}-{3:3}, at: 
> proc_watchdog_thresh+0x37/0xe0
> [  955.838760]  #2: ffffffff83cd4fd0 (cpu_hotplug_lock){....}-{0:0}, at: 
> __lockup_detector_reconfigure+0x14/0x260
> [  955.839163] 3 locks held by kworker/0:3/413:
> [  955.839319]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.839839]  #1: ffffc90000d63e60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.840234]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.840756] 3 locks held by kworker/0:1/3950:
> [  955.840918]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.841272]  #1: ffffc900057abe60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.841836]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.842169] 3 locks held by kworker/0:4/4452:
> [  955.842314]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.842847]  #1: ffffc90000e3fe60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.843307]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.843825] 3 locks held by kworker/3:0/4453:
> [  955.843994]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.844598]  #1: ffffc90000e23e60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.845023]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.845341] 3 locks held by kworker/0:5/4460:
> [  955.845678]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.846045]  #1: ffffc90006273e60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.846677]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.847062] 3 locks held by kworker/3:3/4461:
> [  955.847262]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.847828]  #1: ffffc9000627be60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.848285]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.848794] 3 locks held by kworker/3:4/4464:
> [  955.848954]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.849332]  #1: ffffc9000629be60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.849900]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.850245] 3 locks held by kworker/0:6/4468:
> [  955.850568]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.850947]  #1: ffffc900062bbe60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.851492]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.851870] 3 locks held by kworker/3:5/4472:
> [  955.852014]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.852499]  #1: ffffc900062dbe60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.852911]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.853302] 3 locks held by kworker/3:6/4474:
> [  955.853645]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.854040]  #1: ffffc900062e3e60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.854643]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.854994] 3 locks held by kworker/0:7/4476:
> [  955.855140]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.855747]  #1: ffffc900062f3e60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.856188]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.856707] 3 locks held by kworker/3:7/4479:
> [  955.856879]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.857285]  #1: ffffc90006313e60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.857929]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.858318] 3 locks held by kworker/0:8/4483:
> [  955.858669]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.859082]  #1: ffffc90006333e60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.859766]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.860173] 3 locks held by kworker/3:8/4484:
> [  955.860352]  #0: ffff888100062538 
> ((wq_completion)events){....}-{0:0}, at: 
> process_scheduled_works+0x161/0x8a0
> [  955.860911]  #1: ffffc9000633be60 
> ((work_completion)(&cgrp->bpf.release_work)){....}-{0:0}, at: 
> process_scheduled_0
> [  955.861286]  #2: ffffffff83e5ab88 (cgroup_mutex){....}-{3:3}, at: 
> cgroup_bpf_release+0xcf/0x4d0
> [  955.861811] 3 locks held by kworker/0:9/4491:
>
> Regards,
> Ridong