linux-kernel - Re: [RFC PATCH v1 15/22] PCI/eeepc: use PCI bus lock to avoid race conditions

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Message-ID: <CAErSpo5ZQmzusUMuB7TobCH-Bzw=r78h8SGQ88-WqaH7nRSXkQ@mail.gmail.com>
Date:	Tue, 11 Sep 2012 17:18:03 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Jiang Liu <liuj97@...il.com>
Cc:	Don Dutile <ddutile@...hat.com>, Yinghai Lu <yinghai@...nel.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	Jiang Liu <jiang.liu@...wei.com>,
	Taku Izumi <izumi.taku@...fujitsu.com>,
	"Rafael J . Wysocki" <rjw@...k.pl>,
	Yijing Wang <wangyijing@...wei.com>,
	Xinwei Hu <huxinwei@...wei.com>, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org
Subject: Re: [RFC PATCH v1 15/22] PCI/eeepc: use PCI bus lock to avoid race conditions

On Tue, Aug 7, 2012 at 10:10 AM, Jiang Liu <liuj97@...il.com> wrote:
> This patch uses PCI bus lock mechanism to avoid race conditions when doing
> PCI device hotplug through eeepc driver.

> It also fixes a PCI device reference
> count leakage issue because acpi_get_pci_dev() holds a reference to the
> device returned.

Can you split this refcount fix out as a separate patch?  That looks
pretty straightforward, unlike the bus lock stuff.

> Signed-off-by: Jiang Liu <liuj97@...il.com>
> ---
>  drivers/platform/x86/eeepc-laptop.c |   20 ++++++++++++++------
>  1 file changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/platform/x86/eeepc-laptop.c b/drivers/platform/x86/eeepc-laptop.c
> index dab91b4..25c4176 100644
> --- a/drivers/platform/x86/eeepc-laptop.c
> +++ b/drivers/platform/x86/eeepc-laptop.c
> @@ -606,16 +606,16 @@ static void eeepc_rfkill_hotplug(struct eeepc_laptop *eeepc, acpi_handle handle)
>                         goto out_unlock;
>                 }
>
> -               bus = port->subordinate;
> +               bus = pci_lock_subordinate(port, PCI_BUS_STATE_WORKING);
>
>                 if (!bus) {
>                         pr_warn("Unable to find PCI bus 1?\n");
> -                       goto out_unlock;
> +                       goto out_put_dev;
>                 }
>
>                 if (pci_bus_read_config_dword(bus, 0, PCI_VENDOR_ID, &l)) {
>                         pr_err("Unable to read PCI config space?\n");
> -                       goto out_unlock;
> +                       goto out_unlock_bus;
>                 }
>
>                 absent = (l == 0xffffffff);
> @@ -627,7 +627,7 @@ static void eeepc_rfkill_hotplug(struct eeepc_laptop *eeepc, acpi_handle handle)
>                                 absent ? "absent" : "present");
>                         pr_warn("skipped wireless hotplug as probably "
>                                 "inappropriate for this model\n");
> -                       goto out_unlock;
> +                       goto out_unlock_bus;
>                 }
>
>                 if (!blocked) {
> @@ -635,7 +635,7 @@ static void eeepc_rfkill_hotplug(struct eeepc_laptop *eeepc, acpi_handle handle)
>                         if (dev) {
>                                 /* Device already present */
>                                 pci_dev_put(dev);
> -                               goto out_unlock;
> +                               goto out_unlock_bus;
>                         }
>                         dev = pci_scan_single_device(bus, 0);
>                         if (dev) {
> @@ -650,6 +650,11 @@ static void eeepc_rfkill_hotplug(struct eeepc_laptop *eeepc, acpi_handle handle)
>                                 pci_dev_put(dev);
>                         }
>                 }
> +
> +out_unlock_bus:
> +               pci_bus_unlock(bus);
> +out_put_dev:
> +               pci_dev_put(port);
>         }
>
>  out_unlock:
> @@ -757,7 +762,7 @@ static struct hotplug_slot_ops eeepc_hotplug_slot_ops = {
>  static int eeepc_setup_pci_hotplug(struct eeepc_laptop *eeepc)
>  {
>         int ret = -ENOMEM;
> -       struct pci_bus *bus = pci_find_bus(0, 1);
> +       struct pci_bus *bus = pci_get_bus(0, 1);
>
>         if (!bus) {
>                 pr_err("Unable to find wifi PCI bus\n");
> @@ -785,6 +790,8 @@ static int eeepc_setup_pci_hotplug(struct eeepc_laptop *eeepc)
>                 goto error_register;
>         }
>
> +       pci_bus_put(bus);
> +
>         return 0;
>
>  error_register:
> @@ -793,6 +800,7 @@ error_info:
>         kfree(eeepc->hotplug_slot);
>         eeepc->hotplug_slot = NULL;
>  error_slot:
> +       pci_bus_put(bus);
>         return ret;
>  }
>
> --
> 1.7.9.5
>
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