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Re: [Qemu-ppc] [for-2.11 PATCH 13/26] qdev: store DeviceState's canonica
From: |
David Gibson |
Subject: |
Re: [Qemu-ppc] [for-2.11 PATCH 13/26] qdev: store DeviceState's canonical path to use when unparenting |
Date: |
Wed, 26 Jul 2017 15:24:43 +1000 |
User-agent: |
Mutt/1.8.3 (2017-05-23) |
On Tue, Jul 25, 2017 at 08:00:47PM +0200, Greg Kurz wrote:
> From: Michael Roth <address@hidden>
>
> 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 <address@hidden>
> Cc: Paolo Bonzini <address@hidden>
> Signed-off-by: Michael Roth <address@hidden>
> Signed-off-by: Greg Kurz <address@hidden>
> ---
> 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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- Re: [Qemu-ppc] [for-2.11 PATCH 08/26] spapr_drc: add unrealize method to physical DRC class, (continued)
- [Qemu-ppc] [for-2.11 PATCH 09/26] spapr_drc: pass object ownership to parent/owner, Greg Kurz, 2017/07/25
- [Qemu-ppc] [for-2.11 PATCH 10/26] spapr_iommu: pass object ownership to parent/owner, Greg Kurz, 2017/07/25
- [Qemu-ppc] [for-2.11 PATCH 11/26] spapr_iommu: unregister vmstate at unrealize time, Greg Kurz, 2017/07/25
- [Qemu-ppc] [for-2.11 PATCH 12/26] pci: allow cleanup/unregistration of PCI buses, Greg Kurz, 2017/07/25
- [Qemu-ppc] [for-2.11 PATCH 13/26] qdev: store DeviceState's canonical path to use when unparenting, Greg Kurz, 2017/07/25
- Re: [Qemu-ppc] [for-2.11 PATCH 13/26] qdev: store DeviceState's canonical path to use when unparenting,
David Gibson <=
- [Qemu-ppc] [for-2.11 PATCH 14/26] spapr_pci: add PHB unrealize, Greg Kurz, 2017/07/25
- [Qemu-ppc] [for-2.11 PATCH 15/26] spapr: add pseries-2.11 machine type, Greg Kurz, 2017/07/25
- [Qemu-ppc] [for-2.11 PATCH 16/26] spapr: enable PHB hotplug for pseries-2.11, Greg Kurz, 2017/07/25