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Violators will be prosecuted for from ; Tue, 8 Jan 2019 16:50:26 -0000 Date: Tue, 8 Jan 2019 17:50:21 +0100 From: Halil Pasic In-Reply-To: <20190108173113.3c2d830c.cohuck@redhat.com> References: <1545062250-7573-1-git-send-email-akrowiak@linux.ibm.com> <112a03e6-3d6c-1c14-10ab-c9cea09ad388@linux.ibm.com> <20190108173113.3c2d830c.cohuck@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-Id: <20190108175021.003deab9@oc2783563651> Subject: Re: [Qemu-devel] [PATCH v3] qdev/core: fix qbus_is_full() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Cornelia Huck Cc: Tony Krowiak , imammedo@redhat.com, qemu-devel@nongnu.org, Christian Borntraeger , Peter Maydell On Tue, 8 Jan 2019 17:31:13 +0100 Cornelia Huck wrote: > On Tue, 8 Jan 2019 11:08:56 -0500 > Tony Krowiak 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 > > > Reviewed-by: Pierre Morel > > > Reviewed-by: Halil Pasic > > > --- > > > 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. >