Hi, If I run blktests test block/027 the warning and bug shown below appear. It is the first time that I see a complaint like this while running blktests. I have not yet tried to root-cause this issue. root[7931]: run blktests block/027 [ ... ] kernel: ------------[ cut here ]------------ kernel: ODEBUG: init active (active state 0) object type: work_struct hint: css_release_work_fn+0x0/0x480 kernel: WARNING: CPU: 38 PID: 498 at lib/debugobjects.c:502 debug_print_object+0xda/0x110 kernel: Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.0-debian-1.16.0-4 04/01/2014 kernel: Workqueue: cgwb_release cgwb_release_workfn kernel: RIP: 0010:debug_print_object+0xda/0x110 kernel: Call Trace: kernel: <TASK> kernel: __debug_object_init+0x217/0x290 kernel: debug_object_init+0x16/0x20 kernel: __init_work+0x20/0x30 kernel: css_release+0x1f/0xb0 kernel: percpu_ref_put_many.constprop.0+0x150/0x160 kernel: blkcg_destroy_blkgs+0x20b/0x230 kernel: blkcg_unpin_online+0x4e/0x90 kernel: cgwb_release_workfn+0xba/0x210 kernel: process_one_work+0x57d/0xa80 kernel: worker_thread+0x90/0x650 kernel: kthread+0x185/0x1c0 kernel: ret_from_fork+0x1f/0x30 kernel: </TASK> kernel: irq event stamp: 121765 kernel: hardirqs last enabled at (121775): [<ffffffff811ae168>] __up_console_sem+0x58/0x60 kernel: hardirqs last disabled at (121792): [<ffffffff811ae14d>] __up_console_sem+0x3d/0x60 kernel: softirqs last enabled at (121790): [<ffffffff824004d0>] __do_softirq+0x4d0/0x757 kernel: softirqs last disabled at (121785): [<ffffffff810e4e61>] __irq_exit_rcu+0xd1/0x140 kernel: ---[ end trace 0000000000000000 ]--- kernel: BUG: sleeping function called from invalid context at kernel/workqueue.c:3010 kernel: in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 498, name: kworker/38:1 kernel: preempt_count: 0, expected: 0 kernel: RCU nest depth: 1, expected: 0 kernel: 3 locks held by kworker/38:1/498: kernel: #0: ffff888102c6b538 ((wq_completion)cgwb_release){+.+.}-{0:0}, at: process_one_work+0x479/0xa80 kernel: #1: ffff88810357fdf0 ((work_completion)(&wb->release_work)){+.+.}-{0:0}, at: process_one_work+0x479/0xa80 kernel: #2: ffffffff830c52a0 (rcu_read_lock){....}-{1:2}, at: percpu_ref_put_many.constprop.0+0x0/0x160 kernel: CPU: 38 PID: 498 Comm: kworker/38:1 Tainted: G W E 6.1.0-rc6-dbg #5 kernel: Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.0-debian-1.16.0-4 04/01/2014 kernel: Workqueue: cgwb_release cgwb_release_workfn kernel: Call Trace: kernel: <TASK> kernel: show_stack+0x4e/0x53 kernel: dump_stack_lvl+0x51/0x66 kernel: dump_stack+0x10/0x12 kernel: __might_resched.cold+0x173/0x198 kernel: __might_sleep+0x72/0xe0 kernel: start_flush_work+0x30/0x560 kernel: __flush_work+0xf7/0x170 kernel: __cancel_work_timer+0x22a/0x2c0 kernel: work_fixup_init+0x20/0x40 kernel: __debug_object_init+0x23b/0x290 kernel: debug_object_init+0x16/0x20 kernel: __init_work+0x20/0x30 kernel: css_release+0x1f/0xb0 kernel: percpu_ref_put_many.constprop.0+0x150/0x160 kernel: blkcg_destroy_blkgs+0x20b/0x230 kernel: blkcg_unpin_online+0x4e/0x90 kernel: cgwb_release_workfn+0xba/0x210 kernel: process_one_work+0x57d/0xa80 kernel: worker_thread+0x90/0x650 kernel: kthread+0x185/0x1c0 kernel: ret_from_fork+0x1f/0x30 kernel: </TASK> kernel: null_blk: disk nullb0 created kernel: null_blk: module loaded