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BUG: KCSAN: data-race in __blk_mq_sched_dispatch_requests / blk_mq_run_hw_queue

write to 0xffff888102c83010 of 8 bytes by task 5037 on cpu 1:
 INIT_LIST_HEAD include/linux/list.h:36 [inline]
 list_splice_init include/linux/list.h:483 [inline]
 __blk_mq_sched_dispatch_requests+0x16a/0x2a0 block/blk-mq-sched.c:289
 blk_mq_sched_dispatch_requests+0x8f/0xf0 block/blk-mq-sched.c:341
 __blk_mq_run_hw_queue+0xee/0x1c0 block/blk-mq.c:1532
 __blk_mq_delay_run_hw_queue+0x18e/0x340 block/blk-mq.c:1609
 blk_mq_run_hw_queue+0x231/0x260 block/blk-mq.c:1662
 blk_mq_run_hw_queues block/blk-mq.c:1680 [inline]
 blk_mq_requeue_work+0x423/0x490 block/blk-mq.c:816
 process_one_work+0x3e1/0x950 kernel/workqueue.c:2272
 worker_thread+0x635/0xb90 kernel/workqueue.c:2418
 kthread+0x1ff/0x220 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read to 0xffff888102c83010 of 8 bytes by task 9000 on cpu 0:
 list_empty_careful include/linux/list.h:319 [inline]
 blk_mq_hctx_has_pending block/blk-mq.c:72 [inline]
 blk_mq_run_hw_queue+0x12e/0x260 block/blk-mq.c:1658
 blk_mq_submit_bio+0xd0d/0x1020 block/blk-mq.c:2205
 __submit_bio_noacct_mq block/blk-core.c:1022 [inline]
 submit_bio_noacct+0x77d/0x930 block/blk-core.c:1055
 submit_bio+0x1f3/0x360 block/blk-core.c:1125
 submit_bio_wait+0x7c/0x110 block/bio.c:1151
 blkdev_issue_flush+0xc3/0xe0 block/blk-flush.c:444
 ext4_sync_file+0x3eb/0x690 fs/ext4/fsync.c:177
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2715 [inline]
 ext4_buffered_write_iter+0x363/0x3b0 fs/ext4/file.c:276
 ext4_file_write_iter+0x480/0x10b0 fs/ext4/file.c:501
 call_write_iter include/linux/fs.h:1877 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:721
 do_iter_write+0x112/0x4b0 fs/read_write.c:847
 vfs_iter_write+0x4c/0x70 fs/read_write.c:888
 iter_file_splice_write+0x42a/0x780 fs/splice.c:769
 do_splice_from fs/splice.c:865 [inline]
 direct_splice_actor+0x95/0x150 fs/splice.c:1035
 splice_direct_to_actor+0x365/0x660 fs/splice.c:990
 do_splice_direct+0xf5/0x170 fs/splice.c:1078
 do_sendfile+0x574/0xb70 fs/read_write.c:1238
 __do_sys_sendfile64 fs/read_write.c:1299 [inline]
 __se_sys_sendfile64 fs/read_write.c:1285 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1285
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 9000 Comm: syz-executor.2 Not tainted 5.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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