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BUG: KCSAN: data-race in find_next_bit / rcu_report_exp_cpu_mult

write to 0xffffffff85c7d140 of 8 bytes by interrupt on cpu 1:
 rcu_report_exp_cpu_mult+0x4f/0xa0 kernel/rcu/tree_exp.h:244
 rcu_report_exp_rdp+0x6c/0x90 kernel/rcu/tree_exp.h:254
 rcu_exp_handler+0xe5/0x190 kernel/rcu/tree_exp.h:616
 flush_smp_call_function_queue+0x18c/0x2b0 kernel/smp.c:248
 generic_smp_call_function_single_interrupt+0x1c/0x49 kernel/smp.c:193
 smp_call_function_single_interrupt+0x3f/0x100 arch/x86/kernel/smp.c:262
 call_function_single_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:851
 is_atomic kernel/kcsan/core.c:174 [inline]
 should_watch kernel/kcsan/core.c:203 [inline]
 check_access kernel/kcsan/core.c:458 [inline]
 __tsan_read8+0x8a/0x100 kernel/kcsan/core.c:589
 seq_vprintf+0xb5/0xf0 fs/seq_file.c:404
 seq_printf+0x6c/0x90 fs/seq_file.c:418
 s_show+0x189/0x1b0 kernel/kallsyms.c:618
 seq_read+0x7bb/0x9d0 fs/seq_file.c:268
 proc_reg_read+0xe9/0x140 fs/proc/inode.c:223
 __vfs_read+0x67/0xc0 fs/read_write.c:425
 vfs_read fs/read_write.c:461 [inline]
 vfs_read+0x143/0x2c0 fs/read_write.c:446
 ksys_read+0xd5/0x1b0 fs/read_write.c:587
 __do_sys_read fs/read_write.c:597 [inline]
 __se_sys_read fs/read_write.c:595 [inline]
 __x64_sys_read+0x4c/0x60 fs/read_write.c:595
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffffffff85c7d140 of 8 bytes by task 12 on cpu 0:
 _find_next_bit lib/find_bit.c:39 [inline]
 find_next_bit+0x57/0xe0 lib/find_bit.c:70
 sync_rcu_exp_select_node_cpus+0x28e/0x510 kernel/rcu/tree_exp.h:375
 sync_rcu_exp_select_cpus+0x30c/0x590 kernel/rcu/tree_exp.h:439
 rcu_exp_sel_wait_wake kernel/rcu/tree_exp.h:575 [inline]
 wait_rcu_exp_gp+0x25/0x40 kernel/rcu/tree_exp.h:589
 process_one_work+0x3d4/0x890 kernel/workqueue.c:2264
 worker_thread+0xa0/0x800 kernel/workqueue.c:2410
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: rcu_gp wait_rcu_exp_gp
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