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

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Message-ID: <20190611185206.GG3341036@devbig004.ftw2.facebook.com>
Date:   Tue, 11 Jun 2019 11:52:06 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Dmitry Vyukov <dvyukov@...gle.com>
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>
Subject: Re: linux-next boot error: WARNING: workqueue cpumask: online
 intersect > possible intersect

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.

Thanks.

-- 
tejun