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

write to 0xffff8881621050ac of 4 bytes by task 22043 on cpu 1:
 exit_signals+0xe1/0x4a0 kernel/signal.c:2910
 do_exit+0x194/0x1560 kernel/exit.c:782
 kthread+0x1d8/0x1f0 kernel/kthread.c:315
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff8881621050ac of 4 bytes by task 22030 on cpu 0:
 to_kthread kernel/kthread.c:83 [inline]
 kthread_unpark+0x1f/0x150 kernel/kthread.c:557
 kthread_stop+0xa6/0x250 kernel/kthread.c:640
 loop_unprepare_queue drivers/block/loop.c:927 [inline]
 __loop_clr_fd+0x4cb/0x640 drivers/block/loop.c:1258
 loop_clr_fd drivers/block/loop.c:1337 [inline]
 lo_ioctl+0x9eb/0x11f0 drivers/block/loop.c:1695
 blkdev_ioctl+0x1d0/0x3c0 block/ioctl.c:585
 block_ioctl+0x6d/0x80 fs/block_dev.c:1664
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:1069 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:1055
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:1055
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 22030 Comm: syz-executor.1 Not tainted 5.12.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================