syzbot

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BUG: KCSAN: data-race in __blk_mq_sched_dispatch_requests / blk_mq_do_dispatch_sched

write to 0xffff888129633810 of 8 bytes by task 3222 on cpu 1:
 INIT_LIST_HEAD include/linux/list.h:36 [inline]
 list_splice_init include/linux/list.h:465 [inline]
 __blk_mq_sched_dispatch_requests+0x179/0x2a0 block/blk-mq-sched.c:224
 blk_mq_sched_dispatch_requests+0x7c/0xe0 block/blk-mq-sched.c:276
 __blk_mq_run_hw_queue+0xee/0x1c0 block/blk-mq.c:1418
 __blk_mq_delay_run_hw_queue+0x188/0x330 block/blk-mq.c:1495
 blk_mq_run_hw_queue+0x21c/0x240 block/blk-mq.c:1548
 blk_mq_run_hw_queues block/blk-mq.c:1566 [inline]
 blk_mq_requeue_work+0x43f/0x490 block/blk-mq.c:774
 process_one_work+0x3cb/0x990 kernel/workqueue.c:2269
 worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
 kthread+0x210/0x220 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

read to 0xffff888129633810 of 8 bytes by task 3221 on cpu 0:
 list_empty_careful include/linux/list.h:301 [inline]
 blk_mq_do_dispatch_sched+0xe4/0x2b0 block/blk-mq-sched.c:106
 __blk_mq_sched_dispatch_requests+0x1ff/0x2a0 block/blk-mq-sched.c:245
 blk_mq_sched_dispatch_requests+0x7c/0xe0 block/blk-mq-sched.c:276
 __blk_mq_run_hw_queue+0xee/0x1c0 block/blk-mq.c:1418
 blk_mq_run_work_fn+0x30/0x40 block/blk-mq.c:1696
 process_one_work+0x3cb/0x990 kernel/workqueue.c:2269
 worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
 kthread+0x210/0x220 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 3221 Comm: kworker/0:1H Not tainted 5.8.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: kblockd blk_mq_run_work_fn
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