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BUG: KCSAN: data-race in enqueue_timer / wbt_wait

read to 0xffff888129388998 of 8 bytes by task 10409 on cpu 0:
 blk_stat_is_active block/blk-stat.h:131 [inline]
 wbt_wait+0x177/0x250 block/blk-wbt.c:593
 __rq_qos_throttle+0x47/0x70 block/blk-rq-qos.c:72
 rq_qos_throttle block/blk-rq-qos.h:185 [inline]
 blk_mq_make_request+0x29c/0xf60 block/blk-mq.c:1971
 generic_make_request block/blk-core.c:1064 [inline]
 generic_make_request+0x196/0x740 block/blk-core.c:1006
 submit_bio+0x96/0x3c0 block/blk-core.c:1190
 submit_bh_wbc+0x40f/0x460 fs/buffer.c:3095
 submit_bh fs/buffer.c:3101 [inline]
 __sync_dirty_buffer+0xd3/0x210 fs/buffer.c:3187
 sync_dirty_buffer+0x24/0x40 fs/buffer.c:3200
 __ext4_handle_dirty_metadata+0x19c/0x350 fs/ext4/ext4_jbd2.c:300
 ext4_handle_dirty_dirblock+0x20a/0x280 fs/ext4/namei.c:404
 ext4_init_new_dir fs/ext4/namei.c:2738 [inline]
 ext4_mkdir+0x4aa/0x820 fs/ext4/namei.c:2773
 vfs_mkdir+0x283/0x390 fs/namei.c:3807
 ovl_do_mkdir fs/overlayfs/overlayfs.h:125 [inline]
 ovl_mkdir_real fs/overlayfs/dir.c:122 [inline]
 ovl_create_real+0x1ec/0x2c0 fs/overlayfs/dir.c:169
 ovl_workdir_create+0x299/0x3f0 fs/overlayfs/super.c:650

write to 0xffff888129388998 of 8 bytes by task 2629 on cpu 1:
 hlist_add_head include/linux/list.h:787 [inline]
 enqueue_timer+0x6c/0x240 kernel/time/timer.c:540
 __internal_add_timer+0x4f/0x60 kernel/time/timer.c:553
 internal_add_timer kernel/time/timer.c:595 [inline]
 __mod_timer kernel/time/timer.c:1053 [inline]
 mod_timer kernel/time/timer.c:1100 [inline]
 add_timer+0x250/0x550 kernel/time/timer.c:1136
 __queue_delayed_work+0x13b/0x1d0 kernel/workqueue.c:1649
 queue_delayed_work_on+0xf3/0x110 kernel/workqueue.c:1674
 queue_delayed_work include/linux/workqueue.h:509 [inline]
 batadv_nc_start_timer net/batman-adv/network-coding.c:79 [inline]
 batadv_nc_worker+0x29d/0x390 net/batman-adv/network-coding.c:740
 process_one_work+0x3d4/0x890 kernel/workqueue.c:2269
 worker_thread+0xa0/0x800 kernel/workqueue.c:2415
 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: 1 PID: 2629 Comm: kworker/u4:4 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: bat_events batadv_nc_worker
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