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Chen Ridong 993049c9b1 cgroup: split cgroup_destroy_wq into 3 workqueues 
[ Upstream commit 79f919a89c ]

A hung task can occur during [1] LTP cgroup testing when repeatedly
mounting/unmounting perf_event and net_prio controllers with
systemd.unified_cgroup_hierarchy=1. The hang manifests in
cgroup_lock_and_drain_offline() during root destruction.

Related case:
cgroup_fj_function_perf_event cgroup_fj_function.sh perf_event
cgroup_fj_function_net_prio cgroup_fj_function.sh net_prio

Call Trace:
	cgroup_lock_and_drain_offline+0x14c/0x1e8
	cgroup_destroy_root+0x3c/0x2c0
	css_free_rwork_fn+0x248/0x338
	process_one_work+0x16c/0x3b8
	worker_thread+0x22c/0x3b0
	kthread+0xec/0x100
	ret_from_fork+0x10/0x20

Root Cause:

CPU0                            CPU1
mount perf_event                umount net_prio
cgroup1_get_tree                cgroup_kill_sb
rebind_subsystems               // root destruction enqueues
				// cgroup_destroy_wq
// kill all perf_event css
                                // one perf_event css A is dying
                                // css A offline enqueues cgroup_destroy_wq
                                // root destruction will be executed first
                                css_free_rwork_fn
                                cgroup_destroy_root
                                cgroup_lock_and_drain_offline
                                // some perf descendants are dying
                                // cgroup_destroy_wq max_active = 1
                                // waiting for css A to die

Problem scenario:
1. CPU0 mounts perf_event (rebind_subsystems)
2. CPU1 unmounts net_prio (cgroup_kill_sb), queuing root destruction work
3. A dying perf_event CSS gets queued for offline after root destruction
4. Root destruction waits for offline completion, but offline work is
   blocked behind root destruction in cgroup_destroy_wq (max_active=1)

Solution:
Split cgroup_destroy_wq into three dedicated workqueues:
cgroup_offline_wq – Handles CSS offline operations
cgroup_release_wq – Manages resource release
cgroup_free_wq – Performs final memory deallocation

This separation eliminates blocking in the CSS free path while waiting for
offline operations to complete.

[1] https://github.com/linux-test-project/ltp/blob/master/runtest/controllers
Fixes: 334c3679ec ("cgroup: reimplement rebind_subsystems() using cgroup_apply_control() and friends")
Reported-by: Gao Yingjie <gaoyingjie@uniontech.com>
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Suggested-by: Teju Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-09-25 10:58:50 +02:00
..
bpf bpf: Fix oob access in cgroup local storage 2025-09-09 18:54:11 +02:00
cgroup cgroup: split cgroup_destroy_wq into 3 workqueues 2025-09-25 10:58:50 +02:00
configs Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
debug kdb: Do not assume write() callback available 2025-02-21 13:50:09 +01:00
dma dma/pool: Ensure DMA_DIRECT_REMAP allocations are decrypted 2025-09-04 15:26:30 +02:00
entry entry: Respect changes to system call number by trace_sys_enter() 2024-04-03 15:19:44 +02:00
events perf/core: Prevent VMA split of buffer mappings 2025-08-15 12:05:11 +02:00
futex futex: Don't include process MM in futex key on no-MMU 2023-11-20 11:51:50 +01:00
gcov gcov: add support for GCC 14 2024-06-27 13:46:22 +02:00
irq genirq: Make handle_enforce_irqctx() unconditionally available 2025-02-21 13:48:57 +01:00
kcsan kcsan: test: Initialize dummy variable 2025-08-15 12:04:59 +02:00
livepatch livepatch: Fix missing newline character in klp_resolve_symbols() 2023-11-20 11:52:10 +01:00
locking locking/lockdep: Decrease nr_unused_locks if lock unused in zap_class() 2025-04-25 10:43:41 +02:00
module module: Prevent silent truncation of module name in delete_module(2) 2025-08-28 16:26:01 +02:00
power PM: sleep: console: Fix the black screen issue 2025-08-28 16:25:53 +02:00
printk printk: Fix signed integer overflow when defining LOG_BUF_LEN_MAX 2025-02-21 13:49:30 +01:00
rcu rcu: Protect ->defer_qs_iw_pending from data race 2025-08-28 16:25:55 +02:00
sched cpufreq/sched: Explicitly synchronize limits_changed flag handling 2025-09-09 18:54:18 +02:00
time hrtimers: Unconditionally update target CPU base after offline timer migration 2025-09-19 16:29:59 +02:00
trace tracing: Silence warning when chunk allocation fails in trace_pid_write 2025-09-19 16:29:56 +02:00
.gitignore .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
acct.c acct: block access to kernel internal filesystems 2025-03-07 16:56:39 +01:00
async.c async: Introduce async_schedule_dev_nocall() 2024-01-31 16:17:00 -08:00
audit.c audit: Send netlink ACK before setting connection in auditd_set 2024-02-05 20:12:47 +00:00
audit.h audit: remove selinux_audit_rule_update() declaration 2022-09-07 11:30:15 -04:00
audit_fsnotify.c audit: fix potential double free on error path from fsnotify_add_inode_mark 2022-08-22 18:50:06 -04:00
audit_tree.c audit: use fsnotify group lock helpers 2022-04-25 14:37:28 +02:00
audit_watch.c audit: don't WARN_ON_ONCE(!current->mm) in audit_exe_compare() 2023-11-28 17:07:08 +00:00
auditfilter.c ima: Avoid blocking in RCU read-side critical section 2024-07-11 12:47:16 +02:00
auditsc.c audit,io_uring: io_uring openat triggers audit reference count underflow 2023-10-25 12:03:04 +02:00
backtracetest.c treewide: Replace DECLARE_TASKLET() with DECLARE_TASKLET_OLD() 2020-07-30 11:15:58 -07:00
bounds.c bounds: Use the right number of bits for power-of-two CONFIG_NR_CPUS 2024-05-02 16:29:32 +02:00
capability.c xfs: don't generate selinux audit messages for capability testing 2022-03-09 10:32:06 -08:00
cfi.c cfi: Switch to -fsanitize=kcfi 2022-09-26 10:13:13 -07:00
compat.c sched_getaffinity: don't assume 'cpumask_size()' is fully initialized 2023-04-06 12:10:40 +02:00
configs.c proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
context_tracking.c context_tracking: Fix noinstr vs KASAN 2023-03-10 09:33:45 +01:00
cpu.c hrtimers: Handle CPU state correctly on hotplug 2025-01-23 17:17:15 +01:00
cpu_pm.c context_tracking: Take IRQ eqs entrypoints over RCU 2022-07-05 13:32:59 -07:00
crash_core.c vmcoreinfo: add kallsyms_num_syms symbol 2022-08-28 14:02:44 -07:00
crash_dump.c crash_dump: Remove no longer used saved_max_pfn 2020-04-15 11:21:54 +02:00
cred.c cred: switch to using atomic_long_t 2023-12-20 17:00:20 +01:00
delayacct.c delayacct: support re-entrance detection of thrashing accounting 2022-09-26 19:46:07 -07:00
dma.c proc: introduce proc_create_single{,_data} 2018-05-16 07:23:35 +02:00
exec_domain.c proc: introduce proc_create_single{,_data} 2018-05-16 07:23:35 +02:00
exit.c perf: Fix sample vs do_exit() 2025-06-27 11:07:41 +01:00
extable.c context_tracking: Take NMI eqs entrypoints over RCU 2022-07-05 13:32:59 -07:00
fail_function.c kernel/fail_function: fix memory leak with using debugfs_lookup() 2023-03-11 13:55:39 +01:00
fork.c mm: drop the assumption that VM_SHARED always implies writable 2025-08-28 16:26:12 +02:00
freezer.c freezer,sched: Rewrite core freezer logic 2022-09-07 21:53:50 +02:00
gen_kheaders.sh kheaders: Ignore silly-rename files 2025-01-23 17:17:11 +01:00
groups.c security: Add LSM hook to setgroups() syscall 2022-07-15 18:21:49 +00:00
hung_task.c sched: Fix more TASK_state comparisons 2022-09-30 16:50:39 +02:00
iomem.c mm/nvdimm: add is_ioremap_addr and use that to check ioremap address 2019-07-12 11:05:40 -07:00
irq_work.c irq_work: use kasan_record_aux_stack_noalloc() record callstack 2022-04-15 14:49:55 -07:00
jump_label.c jump_label: Fix static_key_slow_dec() yet again 2024-10-17 15:21:29 +02:00
kallsyms.c kallsyms: Add helper kallsyms_on_each_match_symbol() 2023-10-25 12:03:16 +02:00
kallsyms_internal.h kallsyms: Reduce the memory occupied by kallsyms_seqs_of_names[] 2023-10-25 12:03:16 +02:00
kcmp.c Merge branch 'exec-update-lock-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2020-12-15 19:36:48 -08:00
Kconfig.freezer treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Kconfig.hz treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Kconfig.locks locking/rwlock: Provide RT variant 2021-08-17 17:50:51 +02:00
Kconfig.preempt Revert "signal, x86: Delay calling signals in atomic on RT enabled kernels" 2022-03-31 10:36:55 +02:00
kcov.c kcov: mark in_softirq_really() as __always_inline 2025-01-09 13:30:05 +01:00
kexec.c kernel: kexec: copy user-array safely 2023-11-28 17:06:57 +00:00
kexec_core.c kexec: fix a memory leak in crash_shrink_memory() 2023-07-19 16:21:08 +02:00
kexec_elf.c kexec: initialize ELF lowest address to ULONG_MAX 2025-04-10 14:33:36 +02:00
kexec_file.c kexec: support purgatories with .text.hot sections 2023-06-21 16:00:55 +02:00
kexec_internal.h panic, kexec: make __crash_kexec() NMI safe 2022-09-11 21:55:06 -07:00
kheaders.c kheaders: Use array declaration instead of char 2023-05-11 23:03:02 +09:00
kmod.c modules: add CONFIG_MODPROBE_PATH 2021-05-07 00:26:33 -07:00
kprobes.c kprobes: Fix to check symbol prefixes correctly 2024-08-14 13:52:54 +02:00
ksysfs.c kexec: turn all kexec_mutex acquisitions into trylocks 2022-09-11 21:55:06 -07:00
kthread.c kthread: unpark only parked kthread 2024-10-17 15:22:28 +02:00
latencytop.c latencytop: use the last element of latency_record of system 2022-09-11 21:55:12 -07:00
Makefile kernel/numa.c: Move logging out of numa.h 2024-06-12 11:03:16 +02:00
module_signature.c module: harden ELF info handling 2021-01-19 10:24:45 +01:00
notifier.c notifier: Add blocking/atomic_notifier_chain_register_unique_prio() 2022-05-19 19:30:30 +02:00
nsproxy.c Revert "fs/exec: allow to unshare a time namespace on vfork+exec" 2022-09-13 10:38:43 -07:00
numa.c kernel/numa.c: Move logging out of numa.h 2024-06-12 11:03:16 +02:00
padata.c padata: do not leak refcount in reorder_work 2025-06-04 14:40:20 +02:00
panic.c panic: Flush kernel log buffer at the end 2024-04-13 13:04:54 +02:00
params.c module: ensure that kobject_put() is safe for module type kobjects 2025-05-18 08:21:23 +02:00
pid.c pid: add pidfd_prepare() 2025-06-04 14:40:25 +02:00
pid_namespace.c pid: Replace struct pid 1-element array with flex-array 2024-08-29 17:30:18 +02:00
profile.c profiling: remove profile=sleep support 2024-08-14 13:52:50 +02:00
ptrace.c freezer,sched: Rewrite core freezer logic 2022-09-07 21:53:50 +02:00
range.c kernel.h: split out min()/max() et al. helpers 2020-10-16 11:11:19 -07:00
reboot.c kernel/reboot: emergency_restart: Set correct system_state 2023-11-28 17:07:13 +00:00
regset.c regset: kill ->get() 2020-07-27 14:31:12 -04:00
relay.c relayfs: fix out-of-bounds access in relay_file_read 2023-05-11 23:03:03 +09:00
resource.c resource: fix region_intersects() vs add_memory_driver_managed() 2024-10-17 15:21:55 +02:00
resource_kunit.c resource: provide meaningful MODULE_LICENSE() in test suite 2020-11-25 18:52:35 +01:00
rseq.c rseq: Fix segfault on registration when rseq_cs is non-zero 2025-07-17 18:32:15 +02:00
scftorture.c scftorture: Forgive memory-allocation failure if KASAN 2023-09-23 11:11:00 +02:00
scs.c kasan, vmalloc: only tag normal vmalloc allocations 2022-03-24 19:06:48 -07:00
seccomp.c seccomp: Add wait_killable semantic to seccomp user notifier 2022-05-03 14:11:58 -07:00
signal.c signal: restore the override_rlimit logic 2024-11-14 13:15:18 +01:00
smp.c smp: Add missing destroy_work_on_stack() call in smp_call_on_cpu() 2024-09-12 11:10:24 +02:00
smpboot.c smpboot: use atomic_try_cmpxchg in cpu_wait_death and cpu_report_death 2022-09-11 21:55:10 -07:00
smpboot.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
softirq.c lockdep: Fix wait context check on softirq for PREEMPT_RT 2025-06-04 14:40:03 +02:00
stackleak.c stackleak: add on/off stack variants 2022-05-08 01:33:09 -07:00
stacktrace.c uaccess: remove CONFIG_SET_FS 2022-02-25 09:36:06 +01:00
static_call.c static_call: Don't make __static_call_return0 static 2022-04-05 09:59:38 +02:00
static_call_inline.c x86/static-call: provide a way to do very early static-call updates 2024-12-19 18:08:58 +01:00
stop_machine.c Scheduler changes in this cycle were: 2022-05-24 11:11:13 -07:00
sys.c hrtimer: Use and report correct timerslack values for realtime tasks 2025-03-28 21:58:48 +01:00
sys_ni.c syscalls: fix compat_sys_io_pgetevents_time64 usage 2024-07-05 09:31:59 +02:00
sysctl-test.c kernel/sysctl-test: use SYSCTL_{ZERO/ONE_HUNDRED} instead of i_{zero/one_hundred} 2022-09-08 16:56:45 -07:00
sysctl.c proc: proc_skip_spaces() shouldn't think it is working on C strings 2022-12-05 12:09:06 -08:00
task_work.c task_work: Introduce task_work_cancel() again 2024-08-03 08:49:34 +02:00
taskstats.c genetlink: start to validate reserved header bytes 2022-08-29 12:47:15 +01:00
torture.c torture: Fix hang during kthread shutdown phase 2023-03-10 09:34:07 +01:00
tracepoint.c tracepoint: Optimize the critical region of mutex_lock in tracepoint_module_coming() 2022-09-26 13:01:18 -04:00
tsacct.c taskstats: version 12 with thread group and exe info 2022-04-29 14:38:03 -07:00
ucount.c ucount: fix atomic_long_inc_below() argument type 2025-08-15 12:05:05 +02:00
uid16.c fs: add do_fchownat(), ksys_fchown() helpers and ksys_{,l}chown() wrappers 2018-04-02 20:15:59 +02:00
uid16.h kernel: provide ksys_*() wrappers for syscalls called by kernel/uid16.c 2018-04-02 20:15:30 +02:00
umh.c freezer,umh: Fix call_usermode_helper_exec() vs SIGKILL 2023-02-22 12:59:50 +01:00
up.c A set of locking related fixes and updates: 2021-05-09 13:07:03 -07:00
user-return-notifier.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
user.c fs/epoll: use a per-cpu counter for user's watches count 2021-09-08 11:50:27 -07:00
user_namespace.c ucounts: Split rlimit and ucount values and max values 2022-10-09 16:24:05 -07:00
usermode_driver.c blob_to_mnt(): kern_unmount() is needed to undo kern_mount() 2022-05-19 23:25:47 -04:00
utsname.c uts: Use generic ns_common::count 2020-08-19 14:13:20 +02:00
utsname_sysctl.c kernel/utsname_sysctl.c: Fix hostname polling 2022-10-23 12:01:01 -07:00
watch_queue.c watch_queue: fix pipe accounting mismatch 2025-04-10 14:33:30 +02:00
watchdog.c watchdog: move softlockup_panic back to early_param 2023-11-28 17:07:09 +00:00
watchdog_hld.c watchdog/perf: properly initialize the turbo mode timestamp and rearm counter 2024-08-03 08:49:42 +02:00
workqueue.c workqueue: Improve scalability of workqueue watchdog touch 2024-09-12 11:10:27 +02:00
workqueue_internal.h workqueue: Assign a color to barrier work items 2021-08-17 07:49:10 -10:00