linux-kernel - Re: 4.12.0-rc6+: WQ_MEM_RECLAIM hci0:hci_power_off is flushing !WQ_MEM_RECLAIM events:btusb

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Date:   Tue, 27 Jun 2017 19:28:40 +0200
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Tejun Heo <tj@...nel.org>
Cc:     Dominik Brodowski <linux@...inikbrodowski.net>,
        "Gustavo F. Padovan" <gustavo@...ovan.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-bluetooth@...r.kernel.org
Subject: Re: 4.12.0-rc6+: WQ_MEM_RECLAIM hci0:hci_power_off is flushing
 !WQ_MEM_RECLAIM events:btusb_work

Hi Tejun,

>> On my Dell XPS 13 9343 (x86_64), the following warning was logged right
>> after a resume from suspend-to-mem (not on *every* resume, though, so it
>> might be hard to reproduce). The kernel is v4.12.0-rc6+ as of 94a6df251dd0,
>> and I don't really use bluetooth, though the drivers are loaded:
>> 
>> PM: Finishing wakeup.
>> OOM killer enabled.
>> Restarting tasks ... done.
>> Bluetooth: hci0: read Intel version: 370710018002030d00
>> Bluetooth: hci0: Intel Bluetooth firmware file: intel/ibt-hw-37.7.10-fw-1.80.2.3.d.bseq
>> Bluetooth: hci0: Intel Bluetooth firmware patch completed and activated
>> ... <more, unrelated messages>
>> workqueue: WQ_MEM_RECLAIM hci0:hci_power_off is flushing !WQ_MEM_RECLAIM events:btusb_work
> 
> So, WQ_MEM_RECLAIM has to be transitive; otherwise, it doesn't mean
> anything.  I have a hard time believing that bluetooth actually needs
> WQ_MEM_RECLAIM unless people mount nfs through a bluetooth tethered
> phone.  Would it be possible to remove WQ_MEM_RECLAIM from these
> workqueues?

frankly I do not remember. We used what was recommended to use. I know that the only requirement in one case is that it is a truly single workqueue.

Regards

Marcel