linux-kernel - Re: linux-next boot error: WARNING: workqueue cpumask: online intersect

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Date:   Tue, 23 Jul 2019 10:16:24 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     syzbot <syzbot+4d497898effeb1936245@...kaller.appspotmail.com>,
        Lai Jiangshan <jiangshanlai@...il.com>, mwb@...ux.vnet.ibm.com,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Eric Biggers <ebiggers@...gle.com>
Subject: Re: linux-next boot error: WARNING: workqueue cpumask: online
 intersect > possible intersect

On Tue, Jun 11, 2019 at 8:52 PM Tejun Heo <tj@...nel.org> wrote:
>
> Hello,
>
> On Fri, Jun 07, 2019 at 10:45:45AM +0200, Dmitry Vyukov wrote:
> > +workqueue maintainers and Michael who added this WARNING
> >
> > The WARNING was added in 2017, so I guess it's a change somewhere else
> > that triggered it.
> > The WARNING message does not seem to give enough info about the caller
> > (should it be changed to WARN_ONCE to print a stack?). How can be root
> > cause this and unbreak linux-next?
>
> So, during boot, workqueue builds masks of possible cpus of each node
> and stores them on wq_numa_possible_cpumask[] array.  The warning is
> saying that somehow online cpumask of a node became a superset of the
> possible mask, which should never happen.
>
> Dumping all masks in wq_numa_possible_cpumasks[] and cpumask_of_node()
> of each node should show what's going on.

This has reached upstream and all subsystem subtrees, now all Linux
trees are boot broken (except for few that still lack behind):
https://syzkaller.appspot.com/upstream

No new Linux code is tested by syzbot at this point.