linux-kernel - Re: [PATCH v12 06/12] PCI: Create pci_host_bridge before its associated bus in pci_create_root

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Message-ID: <CAE9FiQXuJZnj74dwTbKJCQNJ+OdEbjSB0fpwqh92+WZ_XGnrxQ@mail.gmail.com>
Date:	Thu, 25 Sep 2014 11:15:01 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Liviu Dudau <Liviu.Dudau@....com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>, Arnd Bergmann <arnd@...db.de>,
	Rob Herring <robh+dt@...nel.org>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	Russell King <linux@....linux.org.uk>,
	linux-pci <linux-pci@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Tanmay Inamdar <tinamdar@....com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Sinan Kaya <okaya@...eaurora.org>,
	Jingoo Han <jg1.han@...sung.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Suravee Suthikulanit <suravee.suthikulpanit@....com>,
	linux-arch <linux-arch@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Device Tree ML <devicetree@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v12 06/12] PCI: Create pci_host_bridge before its
 associated bus in pci_create_root_bus.

On Tue, Sep 23, 2014 at 12:01 PM, Liviu Dudau <Liviu.Dudau@....com> wrote:
> Before commit 7b5436635800 the pci_host_bridge was created before the root bus.
> As that commit has added a needless dependency on the bus for pci_alloc_host_bridge()
> the creation order has been changed for no good reason. Revert the order of
> creation as we are going to depend on the pci_host_bridge structure to retrieve the
> domain number of the root bus.
>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Signed-off-by: Liviu Dudau <Liviu.Dudau@....com>
> Acked-by: Grant Likely <grant.likely@...aro.org>
> Reviewed-by: Catalin Marinas <catalin.marinas@....com>
> Tested-by: Tanmay Inamdar <tinamdar@....com>
> ---
>  drivers/pci/probe.c | 32 +++++++++++++++++---------------
>  1 file changed, 17 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index e3cf8a2..5ff72ec 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -515,7 +515,7 @@ static void pci_release_host_bridge_dev(struct device *dev)
>         kfree(bridge);
>  }
>
> -static struct pci_host_bridge *pci_alloc_host_bridge(struct pci_bus *b)
> +static struct pci_host_bridge *pci_alloc_host_bridge(void)
>  {
>         struct pci_host_bridge *bridge;
>
> @@ -524,7 +524,8 @@ static struct pci_host_bridge *pci_alloc_host_bridge(struct pci_bus *b)
>                 return NULL;
>
>         INIT_LIST_HEAD(&bridge->windows);
> -       bridge->bus = b;
> +       bridge->dev.release = pci_release_host_bridge_dev;
> +
>         return bridge;
>  }
>
> @@ -1761,9 +1762,15 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
>         char bus_addr[64];
>         char *fmt;
>
> +       bridge = pci_alloc_host_bridge();
> +       if (!bridge)
> +               return NULL;
> +
> +       bridge->dev.parent = parent;
> +
>         b = pci_alloc_bus();
>         if (!b)
> -               return NULL;
> +               goto err_out;
>
>         b->sysdata = sysdata;
>         b->ops = ops;
> @@ -1772,26 +1779,19 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
>         if (b2) {
>                 /* If we already got to this bus through a different bridge, ignore it */
>                 dev_dbg(&b2->dev, "bus already known\n");
> -               goto err_out;
> +               goto err_bus_out;
>         }
>
> -       bridge = pci_alloc_host_bridge(b);
> -       if (!bridge)
> -               goto err_out;
> -
> -       bridge->dev.parent = parent;
> -       bridge->dev.release = pci_release_host_bridge_dev;
> +       bridge->bus = b;
>         dev_set_name(&bridge->dev, "pci%04x:%02x", pci_domain_nr(b), bus);
>         error = pcibios_root_bridge_prepare(bridge);
> -       if (error) {
> -               kfree(bridge);
> +       if (error)
>                 goto err_out;
> -       }
>
>         error = device_register(&bridge->dev);
>         if (error) {
>                 put_device(&bridge->dev);
> -               goto err_out;
> +               goto err_bus_out;
>         }
>         b->bridge = get_device(&bridge->dev);
>         device_enable_async_suspend(b->bridge);
> @@ -1848,8 +1848,10 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
>  class_dev_reg_err:
>         put_device(&bridge->dev);
>         device_unregister(&bridge->dev);
> -err_out:
> +err_bus_out:
>         kfree(b);
> +err_out:
> +       kfree(bridge);
>         return NULL;
>  }

Hi Bjorn,

Noticed that you put this one into pci/next.

This patch has problem for the class_dev_reg_err path.
as device_unregister(&bridge->dev) will trigger pci_release_host_bridge_dev.
So will have double free for bridge or else.

Please drop this patch from pci/next.

Also looks strange that the patch have long CC list, but just omit me
and Jiang Liu that
touched those code before.

Thanks

Yinghai
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