On 04/08/14 19:42, Konrad Rzeszutek Wilk wrote: > On Mon, Jul 28, 2014 at 02:06:59PM +0100, David Vrabel wrote: >> On 14/07/14 17:18, Konrad Rzeszutek Wilk wrote: >>> 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. >>> >>> CC: stable@xxxxxxxxxxxxxxx >> >> This deadlock is for a rather specific and uncommon use case (manually >> unbinding a PCI while it is passed-through). Is this critical enough to >> warrant a stable backport? > > We seem to trip over it frequently when rebooting a server. > > That is the VF's end up being unbinded while the guests > are being shutdown. And depending on the timing we end up in a deadlock. Ok. I'll add the stable tag. David -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html