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BUG: KCSAN: data-race in pcpu_alloc_noprof / pcpu_balance_workfn

read-write to 0xffffffff88bb27ac of 4 bytes by task 3340 on cpu 1:
 pcpu_update_empty_pages mm/percpu.c:602 [inline]
 pcpu_chunk_populated mm/percpu.c:1531 [inline]
 pcpu_balance_populated mm/percpu.c:2062 [inline]
 pcpu_balance_workfn+0x94e/0xa60 mm/percpu.c:2212
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3312
 worker_thread+0x526/0x6e0 kernel/workqueue.c:3389
 kthread+0x1d1/0x210 kernel/kthread.c:389
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffffffff88bb27ac of 4 bytes by task 1369 on cpu 0:
 pcpu_alloc_noprof+0x9a7/0x10c0 mm/percpu.c:1894
 fib6_nh_init+0x63a/0x15d0 net/ipv6/route.c:3628
 ip6_route_info_create+0x7b2/0xba0 net/ipv6/route.c:3809
 ip6_route_add+0x26/0x120 net/ipv6/route.c:3853
 addrconf_prefix_route net/ipv6/addrconf.c:2486 [inline]
 addrconf_add_linklocal+0x29c/0x390 net/ipv6/addrconf.c:3317
 addrconf_addr_gen+0x278/0x450 net/ipv6/addrconf.c:3446
 addrconf_init_auto_addrs+0x586/0x6b0
 addrconf_notify+0x7ae/0x950 net/ipv6/addrconf.c:3743
 notifier_call_chain kernel/notifier.c:93 [inline]
 raw_notifier_call_chain+0x6f/0x1d0 kernel/notifier.c:461
 call_netdevice_notifiers_info+0xae/0x100 net/core/dev.c:1994
 netdev_state_change+0x80/0xc0 net/core/dev.c:1376
 linkwatch_do_dev+0xb9/0xf0 net/core/link_watch.c:177
 __linkwatch_run_queue+0x284/0x510 net/core/link_watch.c:234
 linkwatch_event+0x40/0x50 net/core/link_watch.c:277
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3312
 worker_thread+0x526/0x6e0 kernel/workqueue.c:3389
 kthread+0x1d1/0x210 kernel/kthread.c:389
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x00000001 -> 0x00000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 1369 Comm: kworker/u8:5 Not tainted 6.11.0-rc7-syzkaller-00039-g77f587896757 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
Workqueue: events_unbound linkwatch_event
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