On Tue, 8 Jan 2019 11:08:56 -0500 Tony Krowiak <akrow...@linux.ibm.com> wrote:
> On 12/17/18 10:57 AM, Tony Krowiak wrote: > > The qbus_is_full(BusState *bus) function (qdev_monitor.c) compares the > > max_index > > value of the BusState structure with the max_dev value of the BusClass > > structure > > to determine whether the maximum number of children has been reached for the > > bus. The problem is, the max_index field of the BusState structure does not > > necessarily reflect the number of devices that have been plugged into > > the bus. > > > > Whenever a child device is plugged into the bus, the bus's max_index value > > is > > assigned to the child device and then incremented. If the child is > > subsequently > > unplugged, the value of the max_index does not change and no longer > > reflects the > > number of children. > > > > When the bus's max_index value reaches the maximum number of devices > > allowed for the bus (i.e., the max_dev field in the BusClass structure), > > attempts to plug another device will be rejected claiming that the bus is > > full -- even if the bus is actually empty. > > > > To resolve the problem, a new 'num_children' field is being added to the > > BusState structure to keep track of the number of children plugged into the > > bus. It will be incremented when a child is plugged, and decremented when a > > child is unplugged. > > > > Signed-off-by: Tony Krowiak <akrow...@linux.ibm.com> > > Reviewed-by: Pierre Morel<pmo...@linux.ibm.com> > > Reviewed-by: Halil Pasic <pa...@linux.ibm.com> > > --- > > hw/core/qdev.c | 3 +++ > > include/hw/qdev-core.h | 1 + > > qdev-monitor.c | 2 +- > > 3 files changed, 5 insertions(+), 1 deletion(-) > > Ping ... > I could not determine who the maintainer is for the three files > listed above. I checked the MAINTAINERS file and the prologue of each > individual file. Can someone please tell me who is responsible > for merging these changes? Any additional review comments? > > > > > diff --git a/hw/core/qdev.c b/hw/core/qdev.c > > index 6b3cc55b27c2..956923f33520 100644 > > --- a/hw/core/qdev.c > > +++ b/hw/core/qdev.c > > @@ -59,6 +59,8 @@ static void bus_remove_child(BusState *bus, DeviceState > > *child) > > snprintf(name, sizeof(name), "child[%d]", kid->index); > > QTAILQ_REMOVE(&bus->children, kid, sibling); > > > > + bus->num_children--; > > + > > /* This gives back ownership of kid->child back to us. */ > > object_property_del(OBJECT(bus), name, NULL); > > object_unref(OBJECT(kid->child)); > > @@ -73,6 +75,7 @@ static void bus_add_child(BusState *bus, DeviceState > > *child) > > char name[32]; > > BusChild *kid = g_malloc0(sizeof(*kid)); > > > > + bus->num_children++; > > kid->index = bus->max_index++; Hm... I'm wondering what happens for insane numbers of hotplugging operations here? (Preexisting problem for busses without limit, but busses with a limit could now run into that as well.) > > kid->child = child; > > object_ref(OBJECT(kid->child)); > > diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h > > index a24d0dd566e3..521f0a947ead 100644 > > --- a/include/hw/qdev-core.h > > +++ b/include/hw/qdev-core.h > > @@ -206,6 +206,7 @@ struct BusState { > > HotplugHandler *hotplug_handler; > > int max_index; > > bool realized; > > + int num_children; > > QTAILQ_HEAD(ChildrenHead, BusChild) children; > > QLIST_ENTRY(BusState) sibling; > > }; > > diff --git a/qdev-monitor.c b/qdev-monitor.c > > index 07147c63bf8b..45a8ba49644c 100644 > > --- a/qdev-monitor.c > > +++ b/qdev-monitor.c > > @@ -414,7 +414,7 @@ static DeviceState *qbus_find_dev(BusState *bus, char > > *elem) > > static inline bool qbus_is_full(BusState *bus) > > { > > BusClass *bus_class = BUS_GET_CLASS(bus); > > - return bus_class->max_dev && bus->max_index >= bus_class->max_dev; > > + return bus_class->max_dev && bus->num_children >= bus_class->max_dev; > > } > > > > /* > > The approach the patch takes looks sane to me.