netdev - Re: [PATCH] pci: Avoid reentrant calls to work_on

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Date:	Tue, 14 May 2013 20:32:59 -0400
From:	Or Gerlitz <or.gerlitz@...il.com>
To:	Alexander Duyck <alexander.h.duyck@...el.com>
Cc:	bhelgaas@...gle.com, yinghai@...nel.org, guz.fnst@...fujitsu.com,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.com>
Subject: Re: [PATCH] pci: Avoid reentrant calls to work_on_cpu

On Tue, May 14, 2013 at 6:26 PM, Alexander Duyck
<alexander.h.duyck@...el.com> wrote:
>
> This change is meant to fix a deadlock seen when pci_enable_sriov was
> called from within a driver's probe routine.  The issue was that
> work_on_cpu calls flush_work which attempts to flush a work queue for a
> cpu that we are currently working in.  In order to avoid the reentrant
> path we just skip the call to work_on_cpu in the case that the device
> node matches our current node.
>
> Reported-by: Yinghai Lu <yinghai@...nel.org>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>
> ---
>
> This patch is meant to address the issue pointed out in an earlier patch
> sent by Yinghai Lu titled:
>   [PATCH 6/7] PCI: Make sure VF's driver get attached after PF's
>
>  drivers/pci/pci-driver.c |   14 +++++++++-----
>  1 files changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index 79277fb..caeb1c0 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -277,12 +277,16 @@ static int pci_call_probe(struct pci_driver *drv,
> struct pci_dev *dev,
>         int error, node;
>         struct drv_dev_and_id ddi = { drv, dev, id };
>
> -       /* Execute driver initialization on node where the device's
> -          bus is attached to.  This way the driver likely allocates
> -          its local memory on the right node without any need to
> -          change it. */
> +       /*
> +        * Execute driver initialization on the node where the device's
> +        * bus is attached.  This way the driver likely allocates
> +        * its local memory on the right node without any need to
> +        * change it.  If the node is the current node just call
> +        * local_pci_probe and avoid the possibility of reentrant
> +        * calls to work_on_cpu.
> +        */
>         node = dev_to_node(&dev->dev);
> -       if (node >= 0) {
> +       if ((node >= 0) && (node != numa_node_id())) {
>                 int cpu;
>
>                 get_online_cpus();


Alex, FWIW a similar patch was posted by Michael during the last rc
cycles of 3.9 see
http://marc.info/?l=linux-netdev&m=136569426119644&w=2
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