netdev - Re: [PATCHv2 for-3.9] pci: avoid work_on

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Message-ID: <CAErSpo4PM9OhjK83OCQNrS-P6Xx8A3DzTVbDiRLn4dToa9aovA@mail.gmail.com>
Date:	Fri, 19 Apr 2013 10:39:59 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	"Michael S. Tsirkin" <mst@...hat.com>,
	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>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: [PATCHv2 for-3.9] pci: avoid work_on_cpu for nested SRIOV probes

On Thu, Apr 18, 2013 at 9:04 PM, Tejun Heo <tj@...nel.org> wrote:
> So, the thing is there is no actual deadlock. If you're okay with releasing
> w/ spurious lockdep warning, leaving things alone should be fine. An issue
> with mst's patch is that it actually changes the behavior to avoid a
> spurious warning. An alternative course would be leaving it alone now and
> remove the spurious warning during the coming devel cycle and mark it w/
> -stable.

If I understand correctly, you need v3.9-rc1 or later,
CONFIG_PROVE_LOCKING=y, and an SR-IOV device to see the warning.

I like the idea of fixing the spurious warning for v3.10 and
backporting to -stable.  It sounds like there's a cleaner fix in the
works that needs a bit more polishing.  If we need a quick fix sooner,
we'll still have this one in our back       pocket.

Bjorn
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