On Tue, Jul 25, 2017 at 08:00:47PM +0200, Greg Kurz wrote: > From: Michael Roth <mdr...@linux.vnet.ibm.com> > > device_unparent(dev, ...) is called when a device is unparented, > either directly, or as a result of a parent device being > finalized, and handles some final cleanup for the device. Part > of this includes emiting a DEVICE_DELETED QMP event to notify > management, which includes the device's path in the composition > tree as provided by object_get_canonical_path(). > > object_get_canonical_path() assumes the device is still connected > to the machine/root container, and will assert otherwise, but > in some situations this isn't the case: > > If the parent is finalized as a result of object_unparent(), it > will still be attached to the composition tree at the time any > children are unparented as a result of that same call to > object_unparent(). However, in some cases, object_unparent() > will complete without finalizing the parent device, due to > lingering references that won't be released till some time later. > One such example is if the parent has MemoryRegion children (which > take a ref on their parent), who in turn have AddressSpace's (which > take a ref on their regions), since those AddressSpaces get cleaned > up asynchronously by the RCU thread. > > In this case qdev:device_unparent() may be called for a child Device > that no longer has a path to the root/machine container, causing > object_get_canonical_path() to assert. > > Fix this by storing the canonical path during realize() so the > information will still be available for device_unparent() in such > cases.
Hm. I'm no expert on the QOM model, but I'm not sure this is the right approach. I would have thought the right time to emit the DEVICE_DELETED message would be when the device leaves the main composition tree, even if it could be finalized later. If we made that the case, does this problem go away? > Cc: Michael S. Tsirkin <m...@redhat.com> > Cc: Paolo Bonzini <pbonz...@redhat.com> > Signed-off-by: Michael Roth <mdr...@linux.vnet.ibm.com> > Signed-off-by: Greg Kurz <gr...@kaod.org> > --- > Changes since RFC: > - rebased against ppc-for-2.10 > --- > hw/core/qdev.c | 15 ++++++++++++--- > include/hw/qdev-core.h | 1 + > 2 files changed, 13 insertions(+), 3 deletions(-) > > diff --git a/hw/core/qdev.c b/hw/core/qdev.c > index 606ab53c42cd..a64b35c16251 100644 > --- a/hw/core/qdev.c > +++ b/hw/core/qdev.c > @@ -928,6 +928,12 @@ static void device_set_realized(Object *obj, bool value, > Error **errp) > goto post_realize_fail; > } > > + /* always re-initialize since we clean up in device_unparent() > instead > + * of unrealize() > + */ > + g_free(dev->canonical_path); > + dev->canonical_path = object_get_canonical_path(OBJECT(dev)); > + > if (qdev_get_vmsd(dev)) { > if (vmstate_register_with_alias_id(dev, -1, qdev_get_vmsd(dev), > dev, > dev->instance_id_alias, > @@ -984,6 +990,7 @@ child_realize_fail: > } > > post_realize_fail: > + g_free(dev->canonical_path); > if (dc->unrealize) { > dc->unrealize(dev, NULL); > } > @@ -1102,10 +1109,12 @@ static void device_unparent(Object *obj) > > /* Only send event if the device had been completely realized */ > if (dev->pending_deleted_event) { > - gchar *path = object_get_canonical_path(OBJECT(dev)); > + g_assert(dev->canonical_path); > > - qapi_event_send_device_deleted(!!dev->id, dev->id, path, > &error_abort); > - g_free(path); > + qapi_event_send_device_deleted(!!dev->id, dev->id, > dev->canonical_path, > + &error_abort); > + g_free(dev->canonical_path); > + dev->canonical_path = NULL; > } > > qemu_opts_del(dev->opts); > diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h > index ae317286a480..9237b6849ff3 100644 > --- a/include/hw/qdev-core.h > +++ b/include/hw/qdev-core.h > @@ -153,6 +153,7 @@ struct DeviceState { > /*< public >*/ > > const char *id; > + char *canonical_path; > bool realized; > bool pending_deleted_event; > QemuOpts *opts; > -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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