------------[ cut here ]------------
timer_delete_sync(&sdp->delay_work) && rcu_segcblist_n_cbs(&sdp->srcu_cblist)
WARNING: kernel/rcu/srcutree.c:707 at cleanup_srcu_struct+0x3d6/0x8b0, CPU#0: kworker/u9:41/9859
Modules linked in:
CPU: 0 UID: 0 PID: 9859 Comm: kworker/u9:41 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Workqueue: nbd-del nbd_dev_remove_work
RIP: 0010:cleanup_srcu_struct+0x3d6/0x8b0
Code: c1 8b 00 48 83 7d 00 00 4c 8b 74 24 10 0f 85 dd 03 00 00 41 ff c5 41 83 e5 0f 41 83 fd 07 0f 86 e2 fe ff ff e9 ab 00 00 00 90 <0f> 0b 90 4c 8d b5 00 02 00 00 4c 89 f3 48 c1 eb 03 48 b8 00 00 00
RSP: 0018:ffffc90003bdf9d0 EFLAGS: 00010206
RAX: 1ffffd1fdc8c2dad RBX: 0000607d56f38c80 RCX: dffffc0000000000
RDX: 0000000000000001 RSI: ffffffff8e47651f RDI: 00000000ffffffff
RBP: ffffe8fee4616c80 R08: ffffffff907a397f R09: 1ffffffff20f472f
R10: dffffc0000000000 R11: fffffbfff20f4730 R12: ffff88816b18e000
R13: 0000000000000000 R14: ffffe8fee4616d68 R15: 1ffffffff1ce8fde
FS:  0000000000000000(0000) GS:ffff88818d6de000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5919455440 CR3: 00000001128ea000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 blk_mq_free_tag_set+0x617/0x790
 nbd_dev_remove_work+0x4f/0xe0
 process_scheduled_works+0xc3d/0x1630
 worker_thread+0xa47/0xfb0
 kthread+0x38b/0x480
 ret_from_fork+0x514/0xb70
 ret_from_fork_asm+0x1a/0x30
 </TASK>
