On Thu, Jun 23, 2016 at 07:42:18PM +0800, Yijing Wang wrote: > pci_host_bridge holds the top resources(IO port/Mem/bus), > now we release pci_host_bridge resources in > acpi_pci_root_release_info() which would be called when > pci_host_bridge device refcount reach 0. In some cases, > pci_host_bridge refcount cannot reach 0 after we remove > pci root bus in pci_remove_root_bus(). Did you figure out *why* the host bridge refcount is non-zero? That seems like it could be part of the problem. You're moving some release_resource() calls from pci_root.c to host-bridge.c. Where are the corresponding insert or request resource calls? It's more maintainable if we keep the insert and remove paths close in the code. > Then if we want to > hot add pci root bus, we cannot use pci_host_bridge > resources because of conflicts with old resources which are > still in system. I think this is not reasonable. > > 1. For pci devices, we would release their resources in > pci_destroy_dev() regardless of pci device refcount. > 2. When we try to remove pci root bus, there is no devices > need to use the pci_host_bridge resources again, release > pci_host_bridge resources is safe. > 3. In some cases, users woule make mistake, for example, > user get a pci device(increase refcount), but forget to > put this device, then if we do hotplug pci root bus, > it would make all pci devices cannot work after hot add. Can you explain this a little more? Are you talking about a *driver* that forgets to put the device? > I found this issue in the following case: > 1. I have a raid pci device in my system; > 2. I mount a disk which connect to this raid. > 3. hot remove the pci root bus. > 4. hot add the pci root bus. > 5. found the resource conflicts for the children pci devices under this root bus. > > pci_root_bus increase a refcount at pci_host_bridge. > pci_root_bus decrease a refcount at pci_host_bridge in > release_pcibus_dev() when pci_root_bus device refcount reach 0. > > pci_dev increase a refcount at pci_bus in pci_alloc_dev(). > pci_dev decrease a refcount at pci_bus in pci_release_dev() > when pci_dev refcount reach 0. > > If any pci device refcount cannot reach 0, then its pci_bus > refcount cannot reach 0 too, the result is pci_host_bridge > refcount cannot reach 0. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
