From 04162f8f4bcf8c9ae2422def4357289b44208c8c Mon Sep 17 00:00:00 2001 From: Michael Roth Date: Mon, 16 Oct 2017 17:23:13 -0500 Subject: [PATCH] qdev: store DeviceState's canonical path to use when unparenting 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. Cc: Michael S. Tsirkin Cc: Paolo Bonzini Signed-off-by: Michael Roth Signed-off-by: Greg Kurz Signed-off-by: Michael Roth Tested-by: Eric Auger Reviewed-by: David Gibson Message-Id: <20171016222315.407-2-mdroth@linux.vnet.ibm.com> [Clear dev->canonical_path at the post_realize_fail label, which is cleaner. Suggested by David Gibson. - Paolo] Signed-off-by: Paolo Bonzini --- hw/core/qdev.c | 17 ++++++++++++++--- include/hw/qdev-core.h | 1 + 2 files changed, 15 insertions(+), 3 deletions(-) diff --git a/hw/core/qdev.c b/hw/core/qdev.c index 606ab53c42..0019a49503 100644 --- a/hw/core/qdev.c +++ b/hw/core/qdev.c @@ -928,6 +928,13 @@ static void device_set_realized(Object *obj, bool value, Error **errp) goto post_realize_fail; } + /* + * always free/re-initialize here since the value cannot be cleaned up + * in device_unrealize due to its usage later on in the unplug path + */ + 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 +991,8 @@ child_realize_fail: } post_realize_fail: + g_free(dev->canonical_path); + dev->canonical_path = NULL; if (dc->unrealize) { dc->unrealize(dev, NULL); } @@ -1102,10 +1111,12 @@ 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 089146197f..0a71bf83f0 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;