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

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Message-ID: <20130411191717.GB25515@redhat.com>
Date:	Thu, 11 Apr 2013 22:17:17 +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 12:04:08PM -0700, Tejun Heo wrote:
> Hey,
> 
> On Thu, Apr 11, 2013 at 09:58:54PM +0300, Michael S. Tsirkin wrote:
> > > Hmm... how about adding a work_on_cpu_nested() which takes @subclass
> > > argument?  Wouldn't that be much cleaner?
> > > 
> > > Thanks.
> > 
> > Is that 3.9 material though?
> 
> Why wouldn't it be?  It's actually safer as it doesn't change any
> logic.  It's just updating lockdep annotation, which is what's needed
> here anyway.
> 
> Thanks.

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.

> -- 
> tejun
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