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!
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.liu@xxxxxxxxxx>
>> ---
>> 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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