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 13:39:46 -0400
From:   Tejun Heo <tj@...nel.org>
To:     Marcel Holtmann <marcel@...tmann.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

Hello, Marcel.

On Tue, Jun 27, 2017 at 07:28:40PM +0200, Marcel Holtmann wrote:
> >> 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.

Heh, I don't remember either.  I wonder whether there is an existing
dependency chain from network side which triggers the warning.
Dominik, can you please see whether the following patch makes the
warning go away while not triggering new ones?

Thanks.

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index 05686776a5fb..85ec6f7afbf7 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -3047,15 +3047,14 @@ int hci_register_dev(struct hci_dev *hdev)
 
 	BT_DBG("%p name %s bus %d", hdev, hdev->name, hdev->bus);
 
-	hdev->workqueue = alloc_workqueue("%s", WQ_HIGHPRI | WQ_UNBOUND |
-					  WQ_MEM_RECLAIM, 1, hdev->name);
+	hdev->workqueue = alloc_ordered_workqueue("%s", WQ_HIGHPRI, hdev->name);
 	if (!hdev->workqueue) {
 		error = -ENOMEM;
 		goto err;
 	}
 
-	hdev->req_workqueue = alloc_workqueue("%s", WQ_HIGHPRI | WQ_UNBOUND |
-					      WQ_MEM_RECLAIM, 1, hdev->name);
+	hdev->req_workqueue = alloc_ordered_workqueue("%s", WQ_HIGHPRI,
+						      hdev->name);
 	if (!hdev->req_workqueue) {
 		destroy_workqueue(hdev->workqueue);
 		error = -ENOMEM;