On Wed, Aug 29, 2012 at 07:56:43AM +0800, Jiang Liu wrote:
> On 08/29/2012 12:59 AM, Konrad Rzeszutek Wilk wrote:
> > On Tue, Aug 28, 2012 at 11:43:58PM +0800, Jiang Liu wrote:
> >> Following code has a race window between pci_find_bus() and pci_get_slot()
> >> if PCI hotplug operation happens 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.
> >
> > Has this happend in practice? Is this something one can reproduce
> > by manipulating SysFS and at the same time unplugging the PCI
> > devices?
> Hi Konrad,
> We just noticed this issue by code inspection when improving PCI
> hotplug implementation. I guess we could trigger such issue by adding
> some delay between pci_find_bus() and pci_get_slot().
> Regards!
OK. Let me test it out.
> Gerry
>
> >>
> >> struct pci_bus *pci_bus = pci_find_bus(domain, busno);
> >> struct pci_dev *pci_dev = pci_get_slot(pci_bus, devfn);
> >>
> >> Signed-off-by: Jiang Liu <jiang....@huawei.com>
> >> ---
> >> drivers/pci/xen-pcifront.c | 10 ++--------
> >> 1 file changed, 2 insertions(+), 8 deletions(-)
> >>
> >> 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
> >>
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