On Thu, 27 Apr 2017 23:12:32 +0200 Joerg Roedel <j...@8bytes.org> wrote:
> On Thu, Apr 27, 2017 at 08:11:42PM +0200, Gerald Schaefer wrote: > > > +void zpci_destroy_iommu(struct zpci_dev *zdev) > > > +{ > > > + iommu_group_put(zdev->group); > > > + zdev->group = NULL; > > > +} > > > > While the rest of this patch doesn't seem to make much of a difference to > > the current behavior, I'm wondering where this extra iommu_group_put() > > comes from. It either was erroneously missing before this patch, or it > > is erroneously introduced by this patch. > > This is the way to free an iommu-group. It was missing before probably > because it was unclear whether the add_device function allocated a group > or not. So there was no way to know if it needs to be put again in the > remove_device function. Hmm, for the reference count it should not matter whether a new group was allocated or an existing group found with iommu_group_get(). Our add_device callback always gets one reference either from iommu_group_get or _alloc, and then another one from iommu_group_add_device(), after which the first reference is put again. So there should always be one reference more after a successful add_device. Now I'm wondering where this one reference is put again, and I thought that happened in the remove_device callback, where we call iommu_group_remove_device(). Is this not correct? Just want to make sure that we don't have a refcount issue in the current code. Regards, Gerald _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu