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BUG: KCSAN: data-race in __xa_set_mark / xas_find_marked

read-write to 0xffff88810818cfd8 of 8 bytes by task 4695 on cpu 0:
 instrument_read_write include/linux/instrumented.h:56 [inline]
 __instrument_read_write_bitop include/asm-generic/bitops/instrumented-non-atomic.h:84 [inline]
 ___test_and_set_bit include/asm-generic/bitops/instrumented-non-atomic.h:99 [inline]
 node_set_mark lib/xarray.c:95 [inline]
 xas_set_mark lib/xarray.c:893 [inline]
 __xa_set_mark+0xd2/0x1a0 lib/xarray.c:2082
 ref_tracker_debugfs_mark lib/ref_tracker.c:56 [inline]
 ref_tracker_dir_exit+0x5e/0x360 lib/ref_tracker.c:230
 free_netdev+0x305/0x460 net/core/dev.c:12198
 netdev_run_todo+0x7a8/0x8b0 net/core/dev.c:11725
 rtnl_unlock+0xe/0x20 net/core/rtnetlink.c:157
 default_device_exit_batch+0x5db/0x630 net/core/dev.c:13077
 ops_exit_list net/core/net_namespace.c:205 [inline]
 ops_undo_list+0x2ca/0x420 net/core/net_namespace.c:252
 cleanup_net+0x37c/0x5b0 net/core/net_namespace.c:702
 process_one_work kernel/workqueue.c:3314 [inline]
 process_scheduled_works+0x4f0/0x9c0 kernel/workqueue.c:3397
 worker_thread+0x58a/0x780 kernel/workqueue.c:3478
 kthread+0x22a/0x280 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff88810818cfd8 of 8 bytes by task 17928 on cpu 1:
 xas_find_chunk include/linux/xarray.h:1752 [inline]
 xas_find_marked+0x213/0x620 lib/xarray.c:1510
 xa_find_after+0xc6/0x1e0 lib/xarray.c:2251
 debugfs_reap_work+0x18c/0x1d0 lib/ref_tracker.c:510
 process_one_work kernel/workqueue.c:3314 [inline]
 process_scheduled_works+0x4f0/0x9c0 kernel/workqueue.c:3397
 worker_thread+0x58a/0x780 kernel/workqueue.c:3478
 kthread+0x22a/0x280 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x4000020024000000 -> 0x4008020026000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 17928 Comm: kworker/1:8 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: events debugfs_reap_work
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