On Tue, 8 Jan 2019 17:31:13 +0100
Cornelia Huck <coh...@redhat.com> wrote:
> 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.)
>
How does this patch change things? I mean bus->num_children gets
decremented on unplug.
Regards,
Halil
> > > 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.
>
