==================================================================
BUG: KCSAN: data-race in __blk_mq_sched_dispatch_requests / blk_mq_run_hw_queue

write to 0xffff8881299ea010 of 8 bytes by task 3257 on cpu 0:
 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:304
 blk_mq_sched_dispatch_requests+0x9f/0x110 block/blk-mq-sched.c:356
 __blk_mq_run_hw_queue+0xee/0x1c0 block/blk-mq.c:1534
 __blk_mq_delay_run_hw_queue+0x199/0x340 block/blk-mq.c:1611
 blk_mq_run_hw_queue+0x231/0x260 block/blk-mq.c:1664
 blk_mq_run_hw_queues block/blk-mq.c:1682 [inline]
 blk_mq_requeue_work+0x423/0x490 block/blk-mq.c:816
 process_one_work+0x3e1/0x9a0 kernel/workqueue.c:2269
 worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
 kthread+0x20d/0x230 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff8881299ea010 of 8 bytes by interrupt on cpu 1:
 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:1660
 blk_mq_run_hw_queues+0xa2/0x100 block/blk-mq.c:1682
 scsi_run_queue_async drivers/scsi/scsi_lib.c:555 [inline]
 scsi_end_request+0x386/0x400 drivers/scsi/scsi_lib.c:602
 scsi_io_completion+0x105/0xf40 drivers/scsi/scsi_lib.c:938
 scsi_finish_command+0x277/0x2c0 drivers/scsi/scsi.c:214
 scsi_softirq_done+0x271/0x400 drivers/scsi/scsi_lib.c:1464
 blk_done_softirq+0x1a5/0x200 block/blk-mq.c:586
 __do_softirq+0x198/0x360 kernel/softirq.c:298
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
 do_softirq_own_stack+0x5d/0x80 arch/x86/kernel/irq_64.c:77
 invoke_softirq kernel/softirq.c:393 [inline]
 __irq_exit_rcu+0x115/0x120 kernel/softirq.c:423
 common_interrupt+0x14e/0x1e0 arch/x86/kernel/irq.c:239
 asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:572
 preempt_count arch/x86/include/asm/preempt.h:26 [inline]
 get_ctx kernel/kcsan/core.c:193 [inline]
 check_access kernel/kcsan/core.c:601 [inline]
 __tsan_read8+0xf0/0x180 kernel/kcsan/core.c:801
 ext4_file_read_iter+0x21/0x420 fs/ext4/file.c:116
 call_read_iter include/linux/fs.h:1876 [inline]
 generic_file_splice_read+0x22b/0x310 fs/splice.c:312
 do_splice_to fs/splice.c:870 [inline]
 splice_direct_to_actor+0x2a8/0x660 fs/splice.c:950
 do_splice_direct+0xf2/0x170 fs/splice.c:1059
 do_sendfile+0x56a/0xba0 fs/read_write.c:1540
 __do_sys_sendfile64 fs/read_write.c:1595 [inline]
 __se_sys_sendfile64 fs/read_write.c:1587 [inline]
 __x64_sys_sendfile64+0xa9/0x130 fs/read_write.c:1587
 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: 1 PID: 12868 Comm: syz-executor.5 Not tainted 5.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================