linux-kernel - [syzbot ci] Re: block/blk-mq: fix RT kernel performance regressions

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Message-ID: <6946c81e.a70a0220.207337.013a.GAE@google.com>
Date: Sat, 20 Dec 2025 08:00:30 -0800
From: syzbot ci <syzbot+ci366dec97baf89841@...kaller.appspotmail.com>
To: axboe@...nel.dk, djiony2011@...il.com, gregkh@...uxfoundation.org, 
	ionut.nechita@...driver.com, linux-block@...r.kernel.org, 
	linux-kernel@...r.kernel.org, ming.lei@...hat.com, muchun.song@...ux.dev, 
	sashal@...nel.org, stable@...r.kernel.org
Cc: syzbot@...ts.linux.dev, syzkaller-bugs@...glegroups.com
Subject: [syzbot ci] Re: block/blk-mq: fix RT kernel performance regressions

syzbot ci has tested the following series

[v1] block/blk-mq: fix RT kernel performance regressions
https://lore.kernel.org/all/20251220110241.8435-1-ionut.nechita@windriver.com
* [PATCH 1/2] block/blk-mq: fix RT kernel regression with queue_lock in hot path
* [PATCH 2/2] block/blk-mq: convert blk_mq_cpuhp_lock to raw_spinlock for RT

and found the following issues:
* BUG: sleeping function called from invalid context in __cpuhp_state_add_instance
* BUG: sleeping function called from invalid context in __cpuhp_state_remove_instance

Full report is available here:
https://ci.syzbot.org/series/632f4721-6256-44fd-83f5-bf439d5f33f9

***

BUG: sleeping function called from invalid context in __cpuhp_state_add_instance

tree:      torvalds
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux
base:      dd9b004b7ff3289fb7bae35130c0a5c0537266af
arch:      amd64
compiler:  Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
config:    https://ci.syzbot.org/builds/9ad1c682-13b1-4626-b61a-a2156384698d/config
C repro:   https://ci.syzbot.org/findings/f999a055-07f3-4d7a-acfd-8bc0be61e2ec/c_repro
syz repro: https://ci.syzbot.org/findings/f999a055-07f3-4d7a-acfd-8bc0be61e2ec/syz_repro

BUG: sleeping function called from invalid context at ./include/linux/percpu-rwsem.h:51
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 5982, name: syz.0.17
preempt_count: 1, expected: 0
RCU nest depth: 0, expected: 0
INFO: lockdep is turned off.
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 1 UID: 0 PID: 5982 Comm: syz.0.17 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 __might_resched+0x495/0x610 kernel/sched/core.c:8827
 percpu_down_read_internal include/linux/percpu-rwsem.h:51 [inline]
 percpu_down_read include/linux/percpu-rwsem.h:77 [inline]
 cpus_read_lock+0x1b/0x160 kernel/cpu.c:491
 __cpuhp_state_add_instance+0x19/0x40 kernel/cpu.c:2454
 cpuhp_state_add_instance_nocalls include/linux/cpuhotplug.h:401 [inline]
 __blk_mq_add_cpuhp block/blk-mq.c:3858 [inline]
 blk_mq_add_hw_queues_cpuhp+0x19a/0x250 block/blk-mq.c:3906
 blk_mq_realloc_hw_ctxs block/blk-mq.c:4611 [inline]
 blk_mq_init_allocated_queue+0x366/0x1350 block/blk-mq.c:4635
 blk_mq_alloc_queue block/blk-mq.c:4416 [inline]
 __blk_mq_alloc_disk+0x1f0/0x340 block/blk-mq.c:4459
 loop_add+0x411/0xad0 drivers/block/loop.c:2050
 loop_control_ioctl+0x128/0x5a0 drivers/block/loop.c:2216
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1dc598f7c9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffff2134d08 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f1dc5be5fa0 RCX: 00007f1dc598f7c9
RDX: 00000000004080f9 RSI: 0000000000004c80 RDI: 0000000000000003
RBP: 00007f1dc59f297f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1dc5be5fa0 R14: 00007f1dc5be5fa0 R15: 0000000000000003
 </TASK>


***

BUG: sleeping function called from invalid context in __cpuhp_state_remove_instance

tree:      torvalds
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/torvalds/linux
base:      dd9b004b7ff3289fb7bae35130c0a5c0537266af
arch:      amd64
compiler:  Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
config:    https://ci.syzbot.org/builds/9ad1c682-13b1-4626-b61a-a2156384698d/config
C repro:   https://ci.syzbot.org/findings/f39691bc-570a-4163-9791-31ce10e18fb6/c_repro
syz repro: https://ci.syzbot.org/findings/f39691bc-570a-4163-9791-31ce10e18fb6/syz_repro

BUG: sleeping function called from invalid context at ./include/linux/percpu-rwsem.h:51
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 5975, name: syz.0.17
preempt_count: 1, expected: 0
RCU nest depth: 0, expected: 0
INFO: lockdep is turned off.
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 0 UID: 0 PID: 5975 Comm: syz.0.17 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 __might_resched+0x495/0x610 kernel/sched/core.c:8827
 percpu_down_read_internal include/linux/percpu-rwsem.h:51 [inline]
 percpu_down_read include/linux/percpu-rwsem.h:77 [inline]
 cpus_read_lock+0x1b/0x160 kernel/cpu.c:491
 __cpuhp_state_remove_instance+0x77/0x2e0 kernel/cpu.c:2565
 cpuhp_state_remove_instance_nocalls include/linux/cpuhotplug.h:502 [inline]
 __blk_mq_remove_cpuhp+0x140/0x1a0 block/blk-mq.c:3835
 blk_mq_remove_cpuhp block/blk-mq.c:3844 [inline]
 blk_mq_exit_hw_queues block/blk-mq.c:3974 [inline]
 blk_mq_exit_queue+0xe8/0x380 block/blk-mq.c:4670
 __del_gendisk+0x832/0x9e0 block/genhd.c:774
 del_gendisk+0xe8/0x160 block/genhd.c:823
 loop_remove+0x42/0xc0 drivers/block/loop.c:2121
 loop_control_remove drivers/block/loop.c:2180 [inline]
 loop_control_ioctl+0x4ac/0x5a0 drivers/block/loop.c:2218
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f911d78f7c9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd4f0e1fb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f911d9e5fa0 RCX: 00007f911d78f7c9
RDX: 0000000000000006 RSI: 0000000000004c81 RDI: 0000000000000003
RBP: 00007f911d7f297f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f911d9e5fa0 R14: 00007f911d9e5fa0 R15: 0000000000000003
 </TASK>


***

If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
  Tested-by: syzbot@...kaller.appspotmail.com

---
This report is generated by a bot. It may contain errors.
syzbot ci engineers can be reached at syzkaller@...glegroups.com.