[moderation] [block?] KCSAN: data-race in blk_mq_dispatch_rq_list / blk_mq_dispatch_rq_list (9)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 172a9d94339c Merge tag '6.15-rc6-smb3-client-fixes' of git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16036e70580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7bf27d52ff5e6b29
dashboard link: https://syzkaller.appspot.com/bug?extid=d51134e27ad7e147919f
compiler: Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2
CC: [ax...@kernel.dk linux...@vger.kernel.org linux-...@vger.kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/227359b5f25b/disk-172a9d94.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6276da86a755/vmlinux-172a9d94.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6e07cf38c4c8/bzImage-172a9d94.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d51134...@syzkaller.appspotmail.com

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

read-write to 0xffff8881008050f8 of 4 bytes by task 80 on cpu 0:
blk_mq_update_dispatch_busy block/blk-mq.c:1993 [inline]
blk_mq_dispatch_rq_list+0xcbe/0xfe0 block/blk-mq.c:2204
__blk_mq_sched_dispatch_requests+0x1ba/0xd10 block/blk-mq-sched.c:301
blk_mq_sched_dispatch_requests+0x86/0x120 block/blk-mq-sched.c:331
blk_mq_run_work_fn+0x66/0xe0 block/blk-mq.c:2530
process_one_work kernel/workqueue.c:3238 [inline]
process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3319
worker_thread+0x582/0x770 kernel/workqueue.c:3400
kthread+0x489/0x510 kernel/kthread.c:464
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:153
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read-write to 0xffff8881008050f8 of 4 bytes by task 24 on cpu 1:
blk_mq_update_dispatch_busy block/blk-mq.c:1993 [inline]
blk_mq_dispatch_rq_list+0xcbe/0xfe0 block/blk-mq.c:2204
__blk_mq_sched_dispatch_requests+0x1ba/0xd10 block/blk-mq-sched.c:301
blk_mq_sched_dispatch_requests+0x86/0x120 block/blk-mq-sched.c:331
blk_mq_run_hw_queue+0x17e/0x220 block/blk-mq.c:2354
blk_mq_run_hw_queues+0x180/0x250 block/blk-mq.c:2403
blk_mq_requeue_work+0x3b9/0x3f0 block/blk-mq.c:1568
process_one_work kernel/workqueue.c:3238 [inline]
process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3319
worker_thread+0x582/0x770 kernel/workqueue.c:3400
kthread+0x489/0x510 kernel/kthread.c:464
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:153
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x00000006 -> 0x00000007

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 24 Comm: kworker/1:0H Not tainted 6.15.0-rc6-syzkaller-00278-g172a9d94339c #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Workqueue: kblockd blk_mq_requeue_work
==================================================================


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[syzbot]

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