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| author |  Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
| 2014-12-03 16:40:26 -0500 |
|---|---|---|
| committer |  David Vrabel <david.vrabel@citrix.com>
| 2014-12-04 12:41:58 +0000 |
| commit | e8801a7418dda995a70f30874aef77e6d064828e (patch) | |
| tree | ee4e691009b468c5397216b9e5776c6c239cc51e /drivers/xen/xen-pciback/pci_stub.c | |
| parent | swiotlb-xen: pass dev_addr to swiotlb_tbl_unmap_single (diff) | |
| download | linux-e8801a7418dda995a70f30874aef77e6d064828e.tar.gz linux-e8801a7418dda995a70f30874aef77e6d064828e.tar.bz2 linux-e8801a7418dda995a70f30874aef77e6d064828e.zip | |
xen/pciback: Don't deadlock when unbinding.
As commit 0a9fd0152929db372ff61b0d6c280fdd34ae8bdb
'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>
Diffstat (limited to 'drivers/xen/xen-pciback/pci_stub.c')
| -rw-r--r-- | drivers/xen/xen-pciback/pci_stub.c | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c index 017069a455d4..9cbe1a31c1e5 100644 --- a/drivers/xen/xen-pciback/pci_stub.c +++ b/drivers/xen/xen-pciback/pci_stub.c @@ -250,6 +250,8 @@ struct pci_dev *pcistub_get_pci_dev(struct xen_pcibk_device *pdev, * - 'echo BDF > unbind' with a guest still using it. See pcistub_remove * * As such we have to be careful. + * + * To make this easier, the caller has to hold the device lock. */ void pcistub_put_pci_dev(struct pci_dev *dev) { @@ -276,11 +278,8 @@ void pcistub_put_pci_dev(struct pci_dev *dev) /* Cleanup our device * (so it's ready for the next domain) */ - - /* This is OK - we are running from workqueue context - * and want to inhibit the user from fiddling with 'reset' - */ - pci_reset_function(dev); + lockdep_assert_held(&dev->dev.mutex); + __pci_reset_function_locked(dev); pci_restore_state(dev); /* This disables the device. */ @@ -567,7 +566,8 @@ static void pcistub_remove(struct pci_dev *dev) /* N.B. This ends up calling pcistub_put_pci_dev which ends up * doing the FLR. */ xen_pcibk_release_pci_dev(found_psdev->pdev, - found_psdev->dev); + found_psdev->dev, + false /* caller holds the lock. */); } spin_lock_irqsave(&pcistub_devices_lock, flags); |