linux-kernel - Re: [syzbot] INFO: task hung in hci_dev_close

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Date:   Wed, 04 May 2022 11:24:24 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Tejun Heo <tj@...nel.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        "syzkaller-bugs@...glegroups.com" <syzkaller-bugs@...glegroups.com>,
        Hillf Danton <hdanton@...a.com>,
        syzbot <syzbot+c56f6371c48cad0420f9@...kaller.appspotmail.com>
Subject: Re: [syzbot] INFO: task hung in hci_dev_close_sync

On Wed, 2022-05-04 at 05:12 +0000, Tetsuo Handa wrote:
> 
> This seems to be a question regarding commit 87915adc3f0acdf0 ("workqueue: re-add lockdep dependencies for flushing").
> > 
> > syzbot should have been able to catch cancel_work_sync() in work context
> > by checking lockdep_map in __flush_work() for both flush and cancel.
> > 
> > Hillf
> > 
> > --- y/kernel/workqueue.c
> > +++ x/kernel/workqueue.c
> > @@ -3075,10 +3075,10 @@ static bool __flush_work(struct work_str
> >       if (WARN_ON(!work->func))
> >               return false;
> > 
> > -     if (!from_cancel) {
> > +     //if (!from_cancel) {
> > 

I think this is explained in commit d6e89786bed9 ("workqueue: skip
lockdep wq dependency in cancel_work_sync()")

johannes