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xen/pciback: Don't deadlock when unbinding.

Bladeren bron 
As commit 0a9fd01529
'xen/pciback: Document the entry points for 'pcistub_put_pci_dev''
explained there are four entry points in this function.
Two of them are when the user fiddles in the SysFS to
unbind a device which might be in use by a guest or not.

Both 'unbind' states will cause a deadlock as the the PCI lock has
already been taken, which then pci_device_reset tries to take.

We can simplify this by requiring that all callers of
pcistub_put_pci_dev MUST hold the device lock. And then
we can just call the lockless version of pci_device_reset.

To make it even simpler we will modify xen_pcibk_release_pci_dev
to quality whether it should take a lock or not - as it ends
up calling xen_pcibk_release_pci_dev and needs to hold the lock.

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
This commit is contained in:
Konrad Rzeszutek Wilk
2014-12-03 16:40:26 -05:00
gecommit door David Vrabel
bovenliggende 2c3fc8d26d
commit e8801a7418
5 gewijzigde bestanden met toevoegingen van 33 en 16 verwijderingen
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14
drivers/xen/xen-pciback/passthrough.c
Bestand weergeven

@@ -69,7 +69,7 @@ static int __xen_pcibk_add_pci_dev(struct xen_pcibk_device *pdev,
}
static void __xen_pcibk_release_pci_dev(struct xen_pcibk_device *pdev,
struct pci_dev *dev)
struct pci_dev *dev, bool lock)
{
struct passthrough_dev_data *dev_data = pdev->pci_dev_data;
struct pci_dev_entry *dev_entry, *t;
@@ -87,8 +87,13 @@ static void __xen_pcibk_release_pci_dev(struct xen_pcibk_device *pdev,
mutex_unlock(&dev_data->lock);
if (found_dev)
if (found_dev) {
if (lock)
device_lock(&found_dev->dev);
pcistub_put_pci_dev(found_dev);
if (lock)
device_unlock(&found_dev->dev);
}
}
static int __xen_pcibk_init_devices(struct xen_pcibk_device *pdev)
@@ -156,8 +161,11 @@ static void __xen_pcibk_release_devices(struct xen_pcibk_device *pdev)
struct pci_dev_entry *dev_entry, *t;
list_for_each_entry_safe(dev_entry, t, &dev_data->dev_list, list) {
struct pci_dev *dev = dev_entry->dev;
list_del(&dev_entry->list);
pcistub_put_pci_dev(dev_entry->dev);
device_lock(&dev->dev);
pcistub_put_pci_dev(dev);
device_unlock(&dev->dev);
kfree(dev_entry);
}