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BUG: KCSAN: data-race in __rcu_read_unlock / sync_rcu_exp_select_node_cpus

write to 0xffffffff85c843e0 of 8 bytes by task 3950 on cpu 0:
 sync_rcu_exp_select_node_cpus+0x21a/0x500 kernel/rcu/tree_exp.h:376
 sync_rcu_exp_select_cpus+0x31f/0x5a0 kernel/rcu/tree_exp.h:441
 rcu_exp_sel_wait_wake kernel/rcu/tree_exp.h:614 [inline]
 wait_rcu_exp_gp+0x25/0x40 kernel/rcu/tree_exp.h:628
 process_one_work+0x424/0x930 kernel/workqueue.c:2268
 worker_thread+0x9a/0x7e0 kernel/workqueue.c:2414
 kthread+0x203/0x230 kernel/kthread.c:268
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffffffff85c843e0 of 8 bytes by task 32103 on cpu 1:
 rcu_read_unlock_special kernel/rcu/tree_plugin.h:618 [inline]
 __rcu_read_unlock+0x1cf/0x390 kernel/rcu/tree_plugin.h:400
 rcu_read_unlock include/linux/rcupdate.h:654 [inline]
 dput+0x16e/0x700 fs/dcache.c:852
 __fput+0x2b1/0x500 fs/file_table.c:293
 ____fput+0x1b/0x30 fs/file_table.c:313
 task_work_run+0xba/0x120 kernel/task_work.c:123
 get_signal+0x1236/0x1290 kernel/signal.c:2533
 do_signal+0x2b/0x840 arch/x86/kernel/signal.c:784
 exit_to_usermode_loop+0x24a/0x2c0 arch/x86/entry/common.c:161
 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:279 [inline]
 do_syscall_64+0x38b/0x3b0 arch/x86/entry/common.c:305
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 32103 Comm: syz-executor.4 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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