==================================================================
BUG: KCSAN: data-race in exit_signals / kthread_unpark

write to 0xffff88810fa7502c of 4 bytes by task 7836 on cpu 0:
 exit_signals+0x112/0x540 kernel/signal.c:2865
 do_exit+0x194/0x1670 kernel/exit.c:781
 kthread+0x213/0x230 kernel/kthread.c:294
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff88810fa7502c of 4 bytes by task 7864 on cpu 1:
 to_kthread kernel/kthread.c:83 [inline]
 kthread_unpark+0x1f/0x150 kernel/kthread.c:536
 kthread_stop+0xa6/0x2c0 kernel/kthread.c:619
 loop_unprepare_queue drivers/block/loop.c:926 [inline]
 __loop_clr_fd+0x4b4/0x630 drivers/block/loop.c:1257
 lo_release+0xfc/0x120 drivers/block/loop.c:1923
 __blkdev_put+0x40c/0x460 fs/block_dev.c:1588
 blkdev_put+0x222/0x2a0 fs/block_dev.c:1641
 blkdev_close+0x47/0x50 fs/block_dev.c:1649
 __fput+0x263/0x4f0 fs/file_table.c:280
 ____fput+0x11/0x20 fs/file_table.c:313
 task_work_run+0x8e/0x110 kernel/task_work.c:140
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
 exit_to_user_mode_prepare+0x17c/0x1b0 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:301
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7864 Comm: systemd-udevd Not tainted 5.12.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================