netdev - Re: [PATCH repost for-3.9] pci: avoid work_on

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Message-ID: <20130411203053.GC25515@redhat.com>
Date:	Thu, 11 Apr 2013 23:30:53 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Or Gerlitz <ogerlitz@...lanox.com>,
	Ming Lei <ming.lei@...onical.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	David Miller <davem@...emloft.net>,
	Roland Dreier <roland@...nel.org>,
	netdev <netdev@...r.kernel.org>, Yan Burman <yanb@...lanox.com>,
	Jack Morgenstein <jackm@....mellanox.co.il>,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org
Subject: Re: [PATCH repost for-3.9] pci: avoid work_on_cpu for nested SRIOV
 probes

On Thu, Apr 11, 2013 at 12:20:05PM -0700, Tejun Heo wrote:
> On Thu, Apr 11, 2013 at 10:17:17PM +0300, Michael S. Tsirkin wrote:
> > Hmm no, there's a real deadlock here: you are
> > trying to flush from work1 from within work2 running
> > on same workqueue. work2 can't event start running.
> > The problem is not annotation.
> 
> No, that has changed years ago with introduction of cmwq.  System
> workqueues are now expected to have high enough maximum concurrency to
> not cause deadlock as long as memory for worker creation is available,
> so as long as your work item doesn't directly sit in the memory
> reclaim path, it's safe to flush a different work item running on the
> same workqueue with sufficiently high max_active.
> 
> Thanks.

Okay, so you are saying it's a false-positive?
Want to send a patch so Or can try it out?

> -- 
> tejun
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