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Bluetooth hci uses ordered HIGHPRI, MEM_RECLAIM workqueues. It's likely that the flags came from mechanical conversion from create_singlethread_workqueue(). Bluetooth shouldn't be depended upon for memory reclaim and the spurious MEM_RECLAIM flag can trigger the following warning. Remove WQ_MEM_RECLAIM and convert to alloc_ordered_workqueue() while at it. workqueue: WQ_MEM_RECLAIM hci0:hci_power_off is flushing !WQ_MEM_RECLAIM events:btusb_work ------------[ cut here ]------------ WARNING: CPU: 2 PID: 14231 at /home/brodo/local/kernel/git/linux/kernel/workqueue.c:2423 check_flush_dependency+0xb3/0x100 Modules linked in: CPU: 2 PID: 14231 Comm: kworker/u9:4 Not tainted 4.12.0-rc6+ #3 Hardware name: Dell Inc. XPS 13 9343/0TM99H, BIOS A11 12/08/2016 Workqueue: hci0 hci_power_off task: ffff9432dad58000 task.stack: ffff986d43790000 RIP: 0010:check_flush_dependency+0xb3/0x100 RSP: 0018:ffff986d43793c90 EFLAGS: 00010086 RAX: 000000000000005a RBX: ffff943316810820 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000096 RDI: 0000000000000001 RBP: ffff986d43793cb0 R08: 0000000000000775 R09: ffffffff85bdd5c0 R10: 0000000000000040 R11: 0000000000000000 R12: ffffffff84d596e0 R13: ffff9432dad58000 R14: ffff94321c640320 R15: ffff9432dad58000 FS: 0000000000000000(0000) GS:ffff94331f500000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007b8bca242000 CR3: 000000014f60a000 CR4: 00000000003406e0 Call Trace: flush_work+0x8a/0x1c0 ? flush_work+0x184/0x1c0 ? skb_free_head+0x21/0x30 __cancel_work_timer+0x124/0x1b0 ? hci_dev_do_close+0x2a4/0x4d0 cancel_work_sync+0x10/0x20 btusb_close+0x23/0x100 hci_dev_do_close+0x2ca/0x4d0 hci_power_off+0x1e/0x50 process_one_work+0x184/0x3e0 worker_thread+0x4a/0x3a0 ? preempt_count_sub+0x9b/0x100 ? preempt_count_sub+0x9b/0x100 kthread+0x125/0x140 ? process_one_work+0x3e0/0x3e0 ? __kthread_create_on_node+0x1a0/0x1a0 ? do_syscall_64+0x58/0xd0 ret_from_fork+0x27/0x40 Code: 00 75 bf 49 8b 56 18 48 8d 8b b0 00 00 00 48 81 c6 b0 00 00 00 4d 89 e0 48 c7 c7 20 23 6b 85 c6 05 83 cd 31 01 01 e8 bf c4 0c 00 <0f> ff eb 93 80 3d 74 cd 31 01 00 75 a5 65 48 8b 04 25 00 c5 00 ---[ end trace b88fd2f77754bfec ]--- Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.