From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj@kernel.org>
Subject: Re: net/bluetooth: workqueue destruction WARNING in
 hci_unregister_dev
Date: Tue, 13 Sep 2016 11:35:20 -0400
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Cc: Jiri Slaby <jslaby@suse.cz>, Marcel Holtmann <marcel@holtmann.org>,
        Gustavo Padovan <gustavo@padovan.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        linux-bluetooth <linux-bluetooth@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        syzkaller <syzkaller@googlegroups.com>,
        Kostya Serebryany <kcc@google.com>,
        Alexander Potapenko <glider@google.com>,
        Eric Dumazet <edumazet@google.com>,
        Takashi Iwai <tiwai@suse.com>
To: Dmitry Vyukov <dvyukov@google.com>
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Hello,

On Sat, Sep 10, 2016 at 11:33:48AM +0200, Dmitry Vyukov wrote:
> Hit the WARNING with the patch. It showed "Showing busy workqueues and
> worker pools:" after the WARNING, but then no queue info. Was it
> already destroyed and removed from the list?...

Hmm...  It either means that the work item which was in flight when
WARN_ON() ran finished by the time the debug printout got to it or
that it's something unrelated to busy work items.

> [ 198.113838] WARNING: CPU: 2 PID: 26691 at kernel/workqueue.c:4042
> destroy_workqueue+0x17b/0x630

I don't seem to have the same source code that you have.  Which exact
WARN_ON() is this?

Thanks.

-- 
tejun