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BUG: KCSAN: data-race in kick_pool / wq_worker_running

read-write to 0xffff888237c29d64 of 4 bytes by task 10 on cpu 0:
 wq_worker_running+0x95/0x120 kernel/workqueue.c:1404
 schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:7115
 __mutex_lock_common kernel/locking/mutex.c:676 [inline]
 __mutex_lock+0x467/0xcc0 kernel/locking/mutex.c:760
 __mutex_lock_slowpath+0xa/0x10 kernel/locking/mutex.c:1049
 mutex_lock+0x27/0x30 kernel/locking/mutex.c:274
 pcpu_balance_workfn+0x4a/0xc00 mm/percpu.c:2200
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x486/0x510 kernel/kthread.c:463
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff888237c29d64 of 4 bytes by task 3303 on cpu 1:
 need_more_worker kernel/workqueue.c:938 [inline]
 kick_pool+0x49/0x2d0 kernel/workqueue.c:1244
 __queue_work+0x8cb/0xb50 kernel/workqueue.c:2340
 queue_work_on+0xd1/0x160 kernel/workqueue.c:2390
 __lru_add_drain_all+0x2c6/0x3f0 mm/swap.c:874
 lru_add_drain_all+0x10/0x20 mm/swap.c:888
 invalidate_bdev+0x47/0x70 block/bdev.c:101
 ext4_put_super+0x624/0x7d0 fs/ext4/super.c:1339
 generic_shutdown_super+0xe6/0x210 fs/super.c:643
 kill_block_super+0x2a/0x70 fs/super.c:1766
 ext4_kill_sb+0x42/0x80 fs/ext4/super.c:7395
 deactivate_locked_super+0x72/0x1c0 fs/super.c:474
 deactivate_super+0x97/0xa0 fs/super.c:507
 cleanup_mnt+0x269/0x2e0 fs/namespace.c:1375
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1382
 task_work_run+0x131/0x1a0 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xe4/0x100 kernel/entry/common.c:43
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3303 Comm: syz-executor Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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