KCSAN: data-race in __blk_mq_sched_dispatch_requests / __blk_mq_sched_dispatch_requests (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0477e928 Linux 5.10-rc7
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1269a1ef500000
kernel config: https://syzkaller.appspot.com/x/.config?x=329e76890d0bf5c3
dashboard link: https://syzkaller.appspot.com/bug?extid=7f254b31c6a813e862cc
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [ax...@kernel.dk linux...@vger.kernel.org linux-...@vger.kernel.org]

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7f254b...@syzkaller.appspotmail.com

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

write to 0xffff888102474010 of 8 bytes by task 2980 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: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+0x17d/0x330 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+0x1fd/0x220 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read to 0xffff888102474010 of 8 bytes by task 2981 on cpu 1:
list_empty_careful include/linux/list.h:319 [inline]
__blk_mq_sched_dispatch_requests+0xb1/0x2a0 block/blk-mq-sched.c:286
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_run_work_fn+0x3d/0x50 block/blk-mq.c:1810
process_one_work+0x3e1/0x950 kernel/workqueue.c:2272
worker_thread+0x635/0xb90 kernel/workqueue.c:2418
kthread+0x1fd/0x220 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 2981 Comm: kworker/1:1H Not tainted 5.10.0-rc7-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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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.