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From: Bjorn Helgaas <bhelgaas@google.com>
To: Jiang Liu <liuj97@gmail.com>
Cc: Don Dutile <ddutile@redhat.com>, Yinghai Lu <yinghai@kernel.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>,
	Jiang Liu <jiang.liu@huawei.com>,
	Taku Izumi <izumi.taku@jp.fujitsu.com>,
	"Rafael J . Wysocki" <rjw@sisk.pl>,
	Yijing Wang <wangyijing@huawei.com>,
	Xinwei Hu <huxinwei@huawei.com>,
	linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: [RFC PATCH v1 01/22] PCI: use pci_get_domain_bus_and_slot() to avoid race conditions
Date: Tue, 11 Sep 2012 16:00:38 -0600	[thread overview]
Message-ID: <CAErSpo5nOJBCags9=e1y9ZcSDK9y69mZy=_+x0m_9bK78yVUJg@mail.gmail.com> (raw)
In-Reply-To: <1344355862-2726-2-git-send-email-jiang.liu@huawei.com>

On Tue, Aug 7, 2012 at 10:10 AM, Jiang Liu <liuj97@gmail.com> wrote:
> There's a typical usage pattern to search a PCI device under a specific
> PCI bus (domian, busno) as below:
> struct pci_bus *pci_bus = pci_find_bus(domain, busno);
> struct pci_dev *pci_dev = pci_get_slot(pci_bus, devfn);
>
> The above code has a race window between pci_find_bus() and pci_get_slot()
> if PCI hotplug operations happen between them which removes the pci_bus.
> So use PCI hotplug safe interface pci_get_domain_bus_and_slot() instead,
> which also reduces code complexity.

This makes sense to me.  If we support hotplug, it's fundamentally
unsafe to keep a struct pci_bus * without having a reference or some
way to make sure it doesn't go away.  I think we should try to
eradicate all uses of pci_find_bus() and pci_find_next_bus().

> Signed-off-by: Jiang Liu <liuj97@gmail.com>
> ---
>  arch/ia64/sn/kernel/io_common.c      |    4 +---
>  drivers/gpu/vga/vgaarb.c             |   15 +++------------
>  drivers/pci/hotplug/cpcihp_generic.c |    8 ++------
>  drivers/pci/iov.c                    |    8 ++------
>  drivers/pci/xen-pcifront.c           |   10 ++--------
>  5 files changed, 10 insertions(+), 35 deletions(-)
>
> diff --git a/arch/ia64/sn/kernel/io_common.c b/arch/ia64/sn/kernel/io_common.c
> index fbb5f2f..8630875 100644
> --- a/arch/ia64/sn/kernel/io_common.c
> +++ b/arch/ia64/sn/kernel/io_common.c
> @@ -229,7 +229,6 @@ void sn_pci_fixup_slot(struct pci_dev *dev, struct pcidev_info *pcidev_info,
>  {
>         int segment = pci_domain_nr(dev->bus);
>         struct pcibus_bussoft *bs;
> -       struct pci_bus *host_pci_bus;
>         struct pci_dev *host_pci_dev;
>         unsigned int bus_no, devfn;
>
> @@ -245,8 +244,7 @@ void sn_pci_fixup_slot(struct pci_dev *dev, struct pcidev_info *pcidev_info,
>
>         bus_no = (pcidev_info->pdi_slot_host_handle >> 32) & 0xff;
>         devfn = pcidev_info->pdi_slot_host_handle & 0xffffffff;
> -       host_pci_bus = pci_find_bus(segment, bus_no);
> -       host_pci_dev = pci_get_slot(host_pci_bus, devfn);
> +       host_pci_dev = pci_get_domain_bus_and_slot(segment, bus_no, devfn);
>
>         pcidev_info->host_pci_dev = host_pci_dev;
>         pcidev_info->pdi_linux_pcidev = dev;
> diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c
> index 3df8fc0..b6852b7 100644
> --- a/drivers/gpu/vga/vgaarb.c
> +++ b/drivers/gpu/vga/vgaarb.c
> @@ -1066,7 +1066,6 @@ static ssize_t vga_arb_write(struct file *file, const char __user * buf,
>                 }
>
>         } else if (strncmp(curr_pos, "target ", 7) == 0) {
> -               struct pci_bus *pbus;
>                 unsigned int domain, bus, devfn;
>                 struct vga_device *vgadev;
>
> @@ -1085,19 +1084,11 @@ static ssize_t vga_arb_write(struct file *file, const char __user * buf,
>                         pr_debug("vgaarb: %s ==> %x:%x:%x.%x\n", curr_pos,
>                                 domain, bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
>
> -                       pbus = pci_find_bus(domain, bus);
> -                       pr_debug("vgaarb: pbus %p\n", pbus);
> -                       if (pbus == NULL) {
> -                               pr_err("vgaarb: invalid PCI domain and/or bus address %x:%x\n",
> -                                       domain, bus);
> -                               ret_val = -ENODEV;
> -                               goto done;
> -                       }
> -                       pdev = pci_get_slot(pbus, devfn);
> +                       pdev = pci_get_domain_bus_and_slot(domain, bus, devfn);
>                         pr_debug("vgaarb: pdev %p\n", pdev);
>                         if (!pdev) {
> -                               pr_err("vgaarb: invalid PCI address %x:%x\n",
> -                                       bus, devfn);
> +                               pr_err("vgaarb: invalid PCI address %x:%x:%x\n",
> +                                       domain, bus, devfn);
>                                 ret_val = -ENODEV;
>                                 goto done;
>                         }
> diff --git a/drivers/pci/hotplug/cpcihp_generic.c b/drivers/pci/hotplug/cpcihp_generic.c
> index 81af764..a6a71c4 100644
> --- a/drivers/pci/hotplug/cpcihp_generic.c
> +++ b/drivers/pci/hotplug/cpcihp_generic.c
> @@ -154,12 +154,8 @@ static int __init cpcihp_generic_init(void)
>         if(!r)
>                 return -EBUSY;
>
> -       bus = pci_find_bus(0, bridge_busnr);
> -       if (!bus) {
> -               err("Invalid bus number %d", bridge_busnr);
> -               return -EINVAL;
> -       }
> -       dev = pci_get_slot(bus, PCI_DEVFN(bridge_slot, 0));
> +       dev = pci_get_domain_bus_and_slot(0, bridge_busnr,
> +                                         PCI_DEVFN(bridge_slot, 0));
>         if(!dev || dev->hdr_type != PCI_HEADER_TYPE_BRIDGE) {
>                 err("Invalid bridge device %s", bridge);
>                 pci_dev_put(dev);
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 74bbaf8..c7d2969 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -152,15 +152,11 @@ failed1:
>  static void virtfn_remove(struct pci_dev *dev, int id, int reset)
>  {
>         char buf[VIRTFN_ID_LEN];
> -       struct pci_bus *bus;
>         struct pci_dev *virtfn;
>         struct pci_sriov *iov = dev->sriov;
>
> -       bus = pci_find_bus(pci_domain_nr(dev->bus), virtfn_bus(dev, id));
> -       if (!bus)
> -               return;
> -
> -       virtfn = pci_get_slot(bus, virtfn_devfn(dev, id));
> +       virtfn = pci_get_domain_bus_and_slot(pci_domain_nr(dev->bus),
> +                       virtfn_bus(dev, id), virtfn_devfn(dev, id));
>         if (!virtfn)
>                 return;
>
> diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
> index d6cc62c..def8d0b 100644
> --- a/drivers/pci/xen-pcifront.c
> +++ b/drivers/pci/xen-pcifront.c
> @@ -982,7 +982,6 @@ static int pcifront_detach_devices(struct pcifront_device *pdev)
>         int err = 0;
>         int i, num_devs;
>         unsigned int domain, bus, slot, func;
> -       struct pci_bus *pci_bus;
>         struct pci_dev *pci_dev;
>         char str[64];
>
> @@ -1032,13 +1031,8 @@ static int pcifront_detach_devices(struct pcifront_device *pdev)
>                         goto out;
>                 }
>
> -               pci_bus = pci_find_bus(domain, bus);
> -               if (!pci_bus) {
> -                       dev_dbg(&pdev->xdev->dev, "Cannot get bus %04x:%02x\n",
> -                               domain, bus);
> -                       continue;
> -               }
> -               pci_dev = pci_get_slot(pci_bus, PCI_DEVFN(slot, func));
> +               pci_dev = pci_get_domain_bus_and_slot(domain, bus,
> +                               PCI_DEVFN(slot, func));
>                 if (!pci_dev) {
>                         dev_dbg(&pdev->xdev->dev,
>                                 "Cannot get PCI device %04x:%02x:%02x.%d\n",
> --
> 1.7.9.5
>

  reply	other threads:[~2012-09-11 22:01 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-08-07 16:10 [RFC PATCH v1 00/22] introduce PCI bus lock to serialize PCI hotplug operations Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 01/22] PCI: use pci_get_domain_bus_and_slot() to avoid race conditions Jiang Liu
2012-09-11 22:00   ` Bjorn Helgaas [this message]
2012-09-12  8:37     ` Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 02/22] PCI: trivial cleanups for drivers/pci/remove.c Jiang Liu
2012-09-11 22:03   ` Bjorn Helgaas
2012-09-12  8:50     ` Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 03/22] PCI: change PCI device management code to better follow device model Jiang Liu
2012-09-11 22:03   ` Bjorn Helgaas
2012-08-07 16:10 ` [RFC PATCH v1 04/22] PCI: split PCI bus device registration into two stages Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 05/22] PCI: introduce pci_bus_{get|put}() to manage PCI bus reference count Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 06/22] PCI: use a global lock to serialize PCI root bridge hotplug operations Jiang Liu
2012-09-11 22:57   ` Bjorn Helgaas
2012-09-12 15:42     ` Jiang Liu
2012-09-12 16:51       ` Bjorn Helgaas
2012-09-13 16:00         ` [PATCH 1/2] PCI: introduce root bridge hotplug safe interfaces to walk root buses Jiang Liu
2012-09-13 17:40           ` Bjorn Helgaas
2012-09-17 15:55             ` Jiang Liu
2012-09-17 16:24               ` Bjorn Helgaas
2012-09-18 21:39                 ` Bjorn Helgaas
2012-09-21 16:07                   ` [PATCH v4] PCI: introduce two interfaces to walk PCI buses Jiang Liu
2012-09-26 20:14                     ` Bjorn Helgaas
2012-09-13 16:00         ` [PATCH 2/2] PCI: remove host bridge hotplug unsafe interface pci_get_next_bus() Jiang Liu
2012-09-17 15:51         ` [RFC PATCH v1 06/22] PCI: use a global lock to serialize PCI root bridge hotplug operations Jiang Liu
2012-09-20 18:49         ` Paul E. McKenney
2012-08-07 16:10 ` [RFC PATCH v1 07/22] PCI: introduce PCI bus lock to serialize PCI " Jiang Liu
2012-09-11 23:24   ` Bjorn Helgaas
2012-08-07 16:10 ` [RFC PATCH v1 08/22] PCI: introduce hotplug safe search interfaces for PCI bus/device Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 09/22] PCI: enhance PCI probe logic to support PCI bus lock mechanism Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 10/22] PCI: enhance PCI bus specific " Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 11/22] PCI: enhance PCI resource assignment " Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 12/22] PCI: enhance PCI remove " Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 13/22] PCI: make each PCI device hold a reference to its parent PCI bus Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 14/22] PCI/sysfs: use PCI bus lock to avoid race conditions Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 15/22] PCI/eeepc: " Jiang Liu
2012-09-11 23:18   ` Bjorn Helgaas
2012-09-12 14:24     ` [PATCH] eeepc-laptop: fix device reference count leakage in eeepc_rfkill_hotplug() Jiang Liu
2012-09-12 19:59       ` Bjorn Helgaas
2012-08-07 16:10 ` [RFC PATCH v1 16/22] PCI/asus-wmi: use PCI bus lock to avoid race conditions Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 17/22] PCI/pciehp: " Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 18/22] PCI/acpiphp: " Jiang Liu
2012-08-07 16:10 ` [RFC PATCH v1 19/22] PCI/x86: enable PCI bus lock mechanism for x86 platforms Jiang Liu
2012-09-11 23:22   ` Bjorn Helgaas
2012-09-12  9:56     ` Jiang Liu
2012-08-07 16:11 ` [RFC PATCH v1 20/22] PCI/IA64: enable PCI bus lock mechanism for IA64 platforms Jiang Liu
2012-08-07 16:11 ` [RFC PATCH v1 21/22] PCI: cleanups for PCI bus lock implementation Jiang Liu
2012-09-11 23:21   ` Bjorn Helgaas
2012-09-12  8:58     ` Jiang Liu
2012-08-07 16:11 ` [RFC PATCH v1 22/22] PCI: unexport pci_root_buses Jiang Liu
2012-08-07 18:11 ` [RFC PATCH v1 00/22] introduce PCI bus lock to serialize PCI hotplug operations Don Dutile
2012-08-08 15:49   ` Jiang Liu

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