====================================================== WARNING: possible circular locking dependency detected 6.15.0-syzkaller-07774-g90b83efa6701 #0 Not tainted ------------------------------------------------------ syz.0.1/5907 is trying to acquire lock: ffffffff8e264eb0 (cpu_hotplug_lock){++++}-{0:0}, at: static_key_slow_inc+0x12/0x30 kernel/jump_label.c:190 but task is already holding lock: ffff8880267c9638 (&q->rq_qos_mutex){+.+.}-{4:4}, at: wbt_init+0x393/0x540 block/blk-wbt.c:923 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&q->rq_qos_mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:601 [inline] __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:746 wbt_init+0x393/0x540 block/blk-wbt.c:923 queue_wb_lat_store+0x354/0x3d0 block/blk-sysfs.c:603 queue_attr_store+0x276/0x320 block/blk-sysfs.c:805 sysfs_kf_write+0xef/0x150 fs/sysfs/file.c:145 kernfs_fop_write_iter+0x354/0x510 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x6c7/0x1150 fs/read_write.c:686 ksys_write+0x12a/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #2 (&q->q_usage_counter(io)#58){++++}-{0:0}: blk_alloc_queue+0x619/0x760 block/blk-core.c:461 blk_mq_alloc_queue+0x175/0x290 block/blk-mq.c:4396 __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4443 nbd_dev_add+0x4a0/0xbc0 drivers/block/nbd.c:1933 nbd_init+0x181/0x320 drivers/block/nbd.c:2670 do_one_initcall+0x120/0x6e0 init/main.c:1257 do_initcall_level init/main.c:1319 [inline] do_initcalls init/main.c:1335 [inline] do_basic_setup init/main.c:1354 [inline] kernel_init_freeable+0x5c2/0x900 init/main.c:1567 kernel_init+0x1c/0x2b0 init/main.c:1457 ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4056 [inline] fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:4070 might_alloc include/linux/sched/mm.h:318 [inline] slab_pre_alloc_hook mm/slub.c:4098 [inline] slab_alloc_node mm/slub.c:4176 [inline] __kmalloc_cache_node_noprof+0x53/0x420 mm/slub.c:4366 kmalloc_node_noprof include/linux/slab.h:928 [inline] alloc_worker kernel/workqueue.c:2647 [inline] create_worker+0x10f/0x7e0 kernel/workqueue.c:2790 workqueue_prepare_cpu+0xb5/0x160 kernel/workqueue.c:6650 cpuhp_invoke_callback+0x3d2/0xa10 kernel/cpu.c:194 __cpuhp_invoke_callback_range+0x101/0x210 kernel/cpu.c:967 cpuhp_invoke_callback_range kernel/cpu.c:991 [inline] cpuhp_up_callbacks kernel/cpu.c:1022 [inline] _cpu_up+0x3f5/0x930 kernel/cpu.c:1687 cpu_up+0x1dc/0x240 kernel/cpu.c:1719 cpuhp_bringup_mask+0xd8/0x210 kernel/cpu.c:1785 cpuhp_bringup_cpus_parallel kernel/cpu.c:1875 [inline] bringup_nonboot_cpus+0x176/0x1c0 kernel/cpu.c:1889 smp_init+0x34/0x160 kernel/smp.c:1010 kernel_init_freeable+0x3a8/0x900 init/main.c:1559 kernel_init+0x1c/0x2b0 init/main.c:1457 ret_from_fork+0x5d7/0x6f0 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 (cpu_hotplug_lock){++++}-{0:0}: check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain kernel/locking/lockdep.c:3911 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240 lock_acquire kernel/locking/lockdep.c:5871 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828 percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline] percpu_down_read include/linux/percpu-rwsem.h:77 [inline] cpus_read_lock+0x42/0x160 kernel/cpu.c:490 static_key_slow_inc+0x12/0x30 kernel/jump_label.c:190 rq_qos_add+0x2f8/0x4b0 block/blk-rq-qos.c:349 wbt_init+0x3a9/0x540 block/blk-wbt.c:924 queue_wb_lat_store+0x354/0x3d0 block/blk-sysfs.c:603 queue_attr_store+0x276/0x320 block/blk-sysfs.c:805 sysfs_kf_write+0xef/0x150 fs/sysfs/file.c:145 kernfs_fop_write_iter+0x354/0x510 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x6c7/0x1150 fs/read_write.c:686 ksys_write+0x12a/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: cpu_hotplug_lock --> &q->q_usage_counter(io)#58 --> &q->rq_qos_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->rq_qos_mutex); lock(&q->q_usage_counter(io)#58); lock(&q->rq_qos_mutex); rlock(cpu_hotplug_lock); *** DEADLOCK *** 7 locks held by syz.0.1/5907: #0: ffff888035155cf8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2a2/0x370 fs/file.c:1213 #1: ffff88803682e428 (sb_writers#7){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:738 #2: ffff888035b77488 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x28f/0x510 fs/kernfs/file.c:325 #3: ffff888142fa8b48 (kn->active#60){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2b2/0x510 fs/kernfs/file.c:326 #4: ffff8880267c9438 (&q->q_usage_counter(io)#58){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205 #5: ffff8880267c9470 (&q->q_usage_counter(queue)#10){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:205 #6: ffff8880267c9638 (&q->rq_qos_mutex){+.+.}-{4:4}, at: wbt_init+0x393/0x540 block/blk-wbt.c:923 stack backtrace: CPU: 0 UID: 0 PID: 5907 Comm: syz.0.1 Not tainted 6.15.0-syzkaller-07774-g90b83efa6701 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2046 check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2178 check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain kernel/locking/lockdep.c:3911 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240 lock_acquire kernel/locking/lockdep.c:5871 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828 percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline] percpu_down_read include/linux/percpu-rwsem.h:77 [inline] cpus_read_lock+0x42/0x160 kernel/cpu.c:490 static_key_slow_inc+0x12/0x30 kernel/jump_label.c:190 rq_qos_add+0x2f8/0x4b0 block/blk-rq-qos.c:349 wbt_init+0x3a9/0x540 block/blk-wbt.c:924 queue_wb_lat_store+0x354/0x3d0 block/blk-sysfs.c:603 queue_attr_store+0x276/0x320 block/blk-sysfs.c:805 sysfs_kf_write+0xef/0x150 fs/sysfs/file.c:145 kernfs_fop_write_iter+0x354/0x510 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x6c7/0x1150 fs/read_write.c:686 ksys_write+0x12a/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f054e98e969 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:00007f054f84e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f054ebb5fa0 RCX: 00007f054e98e969 RDX: 0000000000000801 RSI: 0000200000000240 RDI: 0000000000000003 RBP: 00007f054ea10ab1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f054ebb5fa0 R15: 00007ffd30f8e498