linux-kernel - Re: [lkp] [workqueue] 82607adcf9: BUG: workqueue lockup - pool cpus=0 flags=0x4 nice=0 stuck for 42s!

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Date:	Mon, 15 Feb 2016 13:59:12 -0500
From:	Tejun Heo <tj@...nel.org>
To:	kernel test robot <ying.huang@...ux.intel.com>
Cc:	lkp@...org, LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Chris Mason <clm@...com>, Michal Hocko <mhocko@...e.com>,
	Ulrich Obergfell <uobergfe@...hat.com>,
	Don Zickus <dzickus@...hat.com>
Subject: Re: [lkp] [workqueue] 82607adcf9: BUG: workqueue lockup - pool
 cpus=0 flags=0x4 nice=0 stuck for 42s!

Hello,

On Sun, Feb 14, 2016 at 09:07:04AM +0800, kernel test robot wrote:
> FYI, we noticed the below changes on
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> commit 82607adcf9cdf40fb7b5331269780c8f70ec6e35 ("workqueue: implement lockup detector")
> 
> 
> [   75.684302] virtio-pci 0000:00:06.0: virtio_pci: leaving for legacy driver
> [   88.791869] ACPI: PCI Interrupt Link [LNKC] enabled at IRQ 11
> [   88.795120] virtio-pci 0000:00:07.0: virtio_pci: leaving for legacy driver
> [   90.789792] BUG: workqueue lockup - pool cpus=0 flags=0x4 nice=0 stuck for 42s!
> [   90.794158] Showing busy workqueues and worker pools:
> [   90.796507] workqueue cgroup_pidlist_destroy: flags=0x0
> [   90.798976]   pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=1/1

Was the VM not executing for a long time?  I can't think why
cgroup_pidlist_destroy would hang for over 40s.

Thanks.

-- 
tejun