linux-kernel - Re: [PATCH] Revert "PCI: Remove from bus_list and release resources in pci_release

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Date:	Fri, 31 Jan 2014 17:56:30 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Revert "PCI: Remove from bus_list and release resources
 in pci_release_dev()"

On Fri, Jan 31, 2014 at 3:34 PM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> Revert commit ef83b0781a73 "PCI: Remove from bus_list and release
> resources in pci_release_dev()" that made some nasty race conditions
> become possible.  For example, if a Thunderbolt link is unplugged
> and then replugged immediately, the pci_release_dev() resulting from
> the hot-remove code path may be racing with the hot-add code path
> which after that commit causes various kinds of breakage to happen
> (up to and including a hard crash of the whole system).
>
> Moreover, the problem that commit ef83b0781a73 attempted to address
> cannot happen any more after commit 8a4c5c329de7 "PCI: Check parent
> kobject in pci_destroy_dev()", because pci_destroy_dev() will now
> return immediately if it has already been executed for the given
> device.
>
> Fixes: ef83b0781a73 (PCI: Remove from bus_list and release resources in pci_release_dev())
> Reported-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 04796c056d12..6e34498ec9f0 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1208,18 +1208,6 @@ static void pci_release_capabilities(struct pci_dev *dev)
>         pci_free_cap_save_buffers(dev);
>  }
>
> -static void pci_free_resources(struct pci_dev *dev)
> -{
> -       int i;
> -
> -       pci_cleanup_rom(dev);
> -       for (i = 0; i < PCI_NUM_RESOURCES; i++) {
> -               struct resource *res = dev->resource + i;
> -               if (res->parent)
> -                       release_resource(res);
> -       }
> -}
> -
>  /**
>   * pci_release_dev - free a pci device structure when all users of it are finished.
>   * @dev: device that's been disconnected
> @@ -1229,14 +1217,9 @@ static void pci_free_resources(struct pci_dev *dev)
>   */
>  static void pci_release_dev(struct device *dev)
>  {
> -       struct pci_dev *pci_dev = to_pci_dev(dev);
> -
> -       down_write(&pci_bus_sem);
> -       list_del(&pci_dev->bus_list);
> -       up_write(&pci_bus_sem);
> -
> -       pci_free_resources(pci_dev);
> +       struct pci_dev *pci_dev;
>
> +       pci_dev = to_pci_dev(dev);
>         pci_release_capabilities(pci_dev);
>         pci_release_of_node(pci_dev);
>         pcibios_release_device(pci_dev);
> diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
> index 4ff36bfa785e..b8c93c90daf5 100644
> --- a/drivers/pci/remove.c
> +++ b/drivers/pci/remove.c
> @@ -3,6 +3,20 @@
>  #include <linux/pci-aspm.h>
>  #include "pci.h"
>
> +static void pci_free_resources(struct pci_dev *dev)
> +{
> +       int i;
> +
> +       msi_remove_pci_irq_vectors(dev);

looks like you are in a rush. Why do you put back msi_remove_pci_irq_vectors?

> +
> +       pci_cleanup_rom(dev);
> +       for (i = 0; i < PCI_NUM_RESOURCES; i++) {
> +               struct resource *res = dev->resource + i;
> +               if (res->parent)
> +                       release_resource(res);
> +       }
> +}
> +
>  static void pci_stop_dev(struct pci_dev *dev)
>  {
>         pci_pme_active(dev, false);
> @@ -25,6 +39,11 @@ static void pci_destroy_dev(struct pci_dev *dev)
>
>         device_del(&dev->dev);
>
> +       down_write(&pci_bus_sem);
> +       list_del(&dev->bus_list);
> +       up_write(&pci_bus_sem);
> +
> +       pci_free_resources(dev);
>         put_device(&dev->dev);
>  }
>
>
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