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KCSAN: data-race in blk_mq_dispatch_rq_list / blk_mq_dispatch_rq_list (10)

Status: auto-obsoleted due to no activity on 2026/01/31 15:15
Subsystems: block
[Documentation on labels]
Reported-by: syzbot+97cd95101437be893150@syzkaller.appspotmail.com
First crash: 198d, last: 198d
▶ ▼ ✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
5ac9d3ae-1932-4ca8-8803-baae2ec4d932 assessment-kcsan 💥 KCSAN: data-race in blk_mq_dispatch_rq_list / blk_mq_dispatch_rq_list (10) 2026/01/10 05:07 2026/01/10 05:07 2026/01/10 05:26 7519916073b761ced56a7b15fdeeb4674e8dc125 
Error 429, Message: You exceeded your current quota, please check your plan and billing details. For more information on this error, head to: https://ai.google.dev/gemini-api/docs/rate-limits. To moni...
truncated to first 200 bytes; open job for full error
▶ ▼ Similar bugs (9)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in blk_mq_dispatch_rq_list / blk_mq_dispatch_rq_list (7) block 6 1 728d 728d 0/29 auto-obsoleted due to no activity on 2024/07/29 01:45
upstream KCSAN: data-race in blk_mq_dispatch_rq_list / blk_mq_dispatch_rq_list (4) block 6 2 1560d 1561d 0/29 auto-closed as invalid on 2022/04/19 11:06
upstream KCSAN: data-race in blk_mq_dispatch_rq_list / blk_mq_dispatch_rq_list (6) block 6 1 784d 784d 0/29 auto-obsoleted due to no activity on 2024/06/03 04:17
upstream KCSAN: data-race in blk_mq_dispatch_rq_list / blk_mq_dispatch_rq_list (3) block 6 1 1608d 1608d 0/29 auto-closed as invalid on 2022/03/02 19:51
upstream KCSAN: data-race in blk_mq_dispatch_rq_list / blk_mq_dispatch_rq_list block 6 2 2447d 2448d 0/29 closed as invalid on 2019/10/18 14:11
upstream KCSAN: data-race in blk_mq_dispatch_rq_list / blk_mq_dispatch_rq_list (2) block 6 1741 1694d 2391d 0/29 auto-closed as invalid on 2021/12/06 01:22
upstream KCSAN: data-race in blk_mq_dispatch_rq_list / blk_mq_dispatch_rq_list (5) block 6 168 821d 928d 0/29 auto-obsoleted due to no activity on 2024/04/27 14:29
upstream KCSAN: data-race in blk_mq_dispatch_rq_list / blk_mq_dispatch_rq_list (9) block 6 1 401d 401d 0/29 auto-obsoleted due to no activity on 2025/07/12 17:32
upstream KCSAN: data-race in blk_mq_dispatch_rq_list / blk_mq_dispatch_rq_list (8) block 6 1 558d 558d 0/29 auto-obsoleted due to no activity on 2025/02/05 17:25

Sample crash report:
==================================================================
BUG: KCSAN: data-race in blk_mq_dispatch_rq_list / blk_mq_dispatch_rq_list

read-write to 0xffff8881008abaf8 of 4 bytes by task 24 on cpu 1:
 blk_mq_update_dispatch_busy block/blk-mq.c:2016 [inline]
 blk_mq_dispatch_rq_list+0xc76/0xf80 block/blk-mq.c:2225
 __blk_mq_sched_dispatch_requests+0x1c8/0xc70 block/blk-mq-sched.c:299
 blk_mq_sched_dispatch_requests+0x86/0x120 block/blk-mq-sched.c:329
 blk_mq_run_hw_queue+0x17e/0x220 block/blk-mq.c:2375
 blk_mq_run_hw_queues+0x18e/0x270 block/blk-mq.c:2424
 blk_mq_requeue_work+0x3b9/0x3f0 block/blk-mq.c:1591
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3340
 worker_thread+0x582/0x770 kernel/workqueue.c:3421
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x149/0x290 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

read to 0xffff8881008abaf8 of 4 bytes by task 48 on cpu 0:
 blk_mq_update_dispatch_busy block/blk-mq.c:2006 [inline]
 blk_mq_dispatch_rq_list+0x8d3/0xf80 block/blk-mq.c:2229
 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
 blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
 __blk_mq_sched_dispatch_requests+0x7eb/0xc70 block/blk-mq-sched.c:307
 blk_mq_sched_dispatch_requests+0x86/0x120 block/blk-mq-sched.c:329
 blk_mq_run_work_fn+0x66/0xe0 block/blk-mq.c:2551
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3340
 worker_thread+0x582/0x770 kernel/workqueue.c:3421
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x149/0x290 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

value changed: 0x00000003 -> 0x00000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 48 Comm: kworker/0:1H Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: kblockd blk_mq_run_work_fn
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/06 15:14 upstream 416f99c3b16f d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in blk_mq_dispatch_rq_list / blk_mq_dispatch_rq_list
* Struck through repros no longer work on HEAD.