[Qemu-devel] [PATCH 0/4] Fix usb-ccid hotplug regression

[Qemu-devel] [PATCH 0/4] Fix usb-ccid hotplug regression

[Marc-André Lureau]

Hi,

The following series fixes the usb-ccid hotplug regression introduced
by commit 675f22c6d3b0: the plugged device is not completely removed
on device_del anymore, due to an extra reference added when doing
set_link(). It turns out the memory management of qdev bus/child is a
bit weird, this is my attempt to improve the situation and fix the
regression.

Fixes:
https://bugzilla.redhat.com/show_bug.cgi?id=1556678

Marc-André Lureau (4):
  bus: do not unref the added child bus on realize
  object: fix OBJ_PROP_LINK_UNREF_ON_RELEASE ambivalence
  usb-ccid: fix bus leak
  usb-hcd-xhci-test: add a test for ccid hotplug

 include/qom/object.h          | 12 +++++++++---
 hw/core/bus.c                 |  1 -
 hw/core/qdev-properties.c     |  2 +-
 hw/core/qdev.c                |  2 +-
 hw/display/xlnx_dp.c          |  2 +-
 hw/dma/xilinx_axidma.c        |  4 ++--
 hw/dma/xlnx-zdma.c            |  2 +-
 hw/i386/pc.c                  |  2 +-
 hw/i386/pc_piix.c             |  2 +-
 hw/i386/pc_q35.c              |  2 +-
 hw/ipmi/ipmi.c                |  2 +-
 hw/net/xilinx_axienet.c       |  4 ++--
 hw/ssi/xilinx_spips.c         |  2 +-
 hw/usb/dev-smartcard-reader.c |  1 +
 net/can/can_host.c            |  2 +-
 net/colo-compare.c            |  2 +-
 qom/object.c                  |  8 +++++---
 target/arm/cpu.c              |  4 ++--
 tests/usb-hcd-xhci-test.c     | 10 ++++++++++
 ui/console.c                  |  2 +-
 20 files changed, 43 insertions(+), 25 deletions(-)


base-commit: c181ddaa176856b3cd2dfd12bbcf25fa9c884a97
-- 
2.17.1.906.g10fd178552

[Qemu-devel] [PATCH 1/4] bus: do not unref the added child bus on realize

[Marc-André Lureau]

When the parent bus removes the child property, it takes care of
removing the added reference, in object_finalize_child_property().

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 hw/core/bus.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/hw/core/bus.c b/hw/core/bus.c
index 4651f24486..ad0c9df335 100644
--- a/hw/core/bus.c
+++ b/hw/core/bus.c
@@ -102,7 +102,6 @@ static void qbus_realize(BusState *bus, DeviceState *parent, const char *name)
         QLIST_INSERT_HEAD(&bus->parent->child_bus, bus, sibling);
         bus->parent->num_child_bus++;
         object_property_add_child(OBJECT(bus->parent), bus->name, OBJECT(bus), NULL);
-        object_unref(OBJECT(bus));
     } else if (bus != sysbus_get_default()) {
         /* TODO: once all bus devices are qdevified,
            only reset handler for main_system_bus should be registered here. */
-- 
2.17.1.906.g10fd178552

[Qemu-devel] [PATCH 2/4] object: fix OBJ_PROP_LINK_UNREF_ON_RELEASE ambivalence

[Marc-André Lureau]

A link property can be set during creation, with
object_property_add_link() and later with object_property_set_link().

add_link() doesn't add a reference to the target object, while
set_link() does.

Furthemore, OBJ_PROP_LINK_UNREF_ON_RELEASE flags, set during add_link,
says whether a reference must be released when the property is destroyed.
This can lead to leaks if the property was later set_link(), as the
added reference is never released.

Instead, rename OBJ_PROP_LINK_UNREF_ON_RELEASE to OBJ_PROP_LINK_STRONG
and use that has an indication on how the link handle reference
management in set_link().

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 include/qom/object.h      | 12 +++++++++---
 hw/core/qdev-properties.c |  2 +-
 hw/core/qdev.c            |  2 +-
 hw/display/xlnx_dp.c      |  2 +-
 hw/dma/xilinx_axidma.c    |  4 ++--
 hw/dma/xlnx-zdma.c        |  2 +-
 hw/i386/pc.c              |  2 +-
 hw/i386/pc_piix.c         |  2 +-
 hw/i386/pc_q35.c          |  2 +-
 hw/ipmi/ipmi.c            |  2 +-
 hw/net/xilinx_axienet.c   |  4 ++--
 hw/ssi/xilinx_spips.c     |  2 +-
 net/can/can_host.c        |  2 +-
 net/colo-compare.c        |  2 +-
 qom/object.c              |  8 +++++---
 target/arm/cpu.c          |  4 ++--
 ui/console.c              |  2 +-
 17 files changed, 32 insertions(+), 24 deletions(-)

diff --git a/include/qom/object.h b/include/qom/object.h
index a0c78c76f7..f3d2308d56 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -1103,6 +1103,11 @@ char *object_property_get_str(Object *obj, const char *name,
  * @errp: returns an error if this function fails
  *
  * Writes an object's canonical path to a property.
+ *
+ * If the link property was created with
+ * <code>OBJ_PROP_LINK_STRONG</code> bit, the old target object is
+ * unreferenced, and a reference is added to the new target object.
+ *
  */
 void object_property_set_link(Object *obj, Object *value,
                               const char *name, Error **errp);
@@ -1394,7 +1399,7 @@ void object_property_add_child(Object *obj, const char *name,
 
 typedef enum {
     /* Unref the link pointer when the property is deleted */
-    OBJ_PROP_LINK_UNREF_ON_RELEASE = 0x1,
+    OBJ_PROP_LINK_STRONG = 0x1,
 } ObjectPropertyLinkFlags;
 
 /**
@@ -1432,8 +1437,9 @@ void object_property_allow_set_link(const Object *, const char *,
  * link property.  The reference count for <code>*@child</code> is
  * managed by the property from after the function returns till the
  * property is deleted with object_property_del().  If the
- * <code>@flags</code> <code>OBJ_PROP_LINK_UNREF_ON_RELEASE</code> bit is set,
- * the reference count is decremented when the property is deleted.
+ * <code>@flags</code> <code>OBJ_PROP_LINK_STRONG</code> bit is set,
+ * the reference count is decremented when the property is deleted or
+ * modified.
  */
 void object_property_add_link(Object *obj, const char *name,
                               const char *type, Object **child,
diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
index 5bbc2d98b5..f3a83a3643 100644
--- a/hw/core/qdev-properties.c
+++ b/hw/core/qdev-properties.c
@@ -1309,7 +1309,7 @@ static void create_link_property(Object *obj, Property *prop, Error **errp)
     object_property_add_link(obj, prop->name, prop->link_type,
                              child,
                              qdev_prop_allow_set_link_before_realize,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              errp);
 }
 
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index f6f92473b8..ce7c316552 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -435,7 +435,7 @@ void qdev_init_gpio_out_named(DeviceState *dev, qemu_irq *pins,
         object_property_add_link(OBJECT(dev), propname, TYPE_IRQ,
                                  (Object **)&pins[i],
                                  object_property_allow_set_link,
-                                 OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                                 OBJ_PROP_LINK_STRONG,
                                  &error_abort);
         g_free(propname);
     }
diff --git a/hw/display/xlnx_dp.c b/hw/display/xlnx_dp.c
index 6715b9cc2b..b737e1d3af 100644
--- a/hw/display/xlnx_dp.c
+++ b/hw/display/xlnx_dp.c
@@ -1221,7 +1221,7 @@ static void xlnx_dp_init(Object *obj)
     object_property_add_link(obj, "dpdma", TYPE_XLNX_DPDMA,
                              (Object **) &s->dpdma,
                              xlnx_dp_set_dpdma,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              &error_abort);
 
     /*
diff --git a/hw/dma/xilinx_axidma.c b/hw/dma/xilinx_axidma.c
index 9b48103574..401a328e27 100644
--- a/hw/dma/xilinx_axidma.c
+++ b/hw/dma/xilinx_axidma.c
@@ -525,12 +525,12 @@ static void xilinx_axidma_realize(DeviceState *dev, Error **errp)
     object_property_add_link(OBJECT(ds), "dma", TYPE_XILINX_AXI_DMA,
                              (Object **)&ds->dma,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              &local_err);
     object_property_add_link(OBJECT(cs), "dma", TYPE_XILINX_AXI_DMA,
                              (Object **)&cs->dma,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              &local_err);
     if (local_err) {
         goto xilinx_axidma_realize_fail;
diff --git a/hw/dma/xlnx-zdma.c b/hw/dma/xlnx-zdma.c
index 8eea757aff..b6745f5bcf 100644
--- a/hw/dma/xlnx-zdma.c
+++ b/hw/dma/xlnx-zdma.c
@@ -787,7 +787,7 @@ static void zdma_init(Object *obj)
     object_property_add_link(obj, "dma", TYPE_MEMORY_REGION,
                              (Object **)&s->dma_mr,
                              qdev_prop_allow_set_link_before_realize,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              &error_abort);
 }
 
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index d768930d02..1aaa60a5d4 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -484,7 +484,7 @@ void pc_cmos_init(PCMachineState *pcms,
                              TYPE_ISA_DEVICE,
                              (Object **)&pcms->rtc,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE, &error_abort);
+                             OBJ_PROP_LINK_STRONG, &error_abort);
     object_property_set_link(OBJECT(pcms), OBJECT(s),
                              "rtc_state", &error_abort);
 
diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index b4c5b03274..3b87f3cedb 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -289,7 +289,7 @@ static void pc_init1(MachineState *machine,
                                  TYPE_HOTPLUG_HANDLER,
                                  (Object **)&pcms->acpi_dev,
                                  object_property_allow_set_link,
-                                 OBJ_PROP_LINK_UNREF_ON_RELEASE, &error_abort);
+                                 OBJ_PROP_LINK_STRONG, &error_abort);
         object_property_set_link(OBJECT(machine), OBJECT(piix4_pm),
                                  PC_MACHINE_ACPI_DEVICE_PROP, &error_abort);
     }
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index 83d6d75efa..087f2630f9 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -194,7 +194,7 @@ static void pc_q35_init(MachineState *machine)
                              TYPE_HOTPLUG_HANDLER,
                              (Object **)&pcms->acpi_dev,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE, &error_abort);
+                             OBJ_PROP_LINK_STRONG, &error_abort);
     object_property_set_link(OBJECT(machine), OBJECT(lpc),
                              PC_MACHINE_ACPI_DEVICE_PROP, &error_abort);
 
diff --git a/hw/ipmi/ipmi.c b/hw/ipmi/ipmi.c
index 9be281fd87..63c031703d 100644
--- a/hw/ipmi/ipmi.c
+++ b/hw/ipmi/ipmi.c
@@ -104,7 +104,7 @@ void ipmi_bmc_find_and_link(Object *obj, Object **bmc)
 {
     object_property_add_link(obj, "bmc", TYPE_IPMI_BMC, bmc,
                              isa_ipmi_bmc_check,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              &error_abort);
 }
 
diff --git a/hw/net/xilinx_axienet.c b/hw/net/xilinx_axienet.c
index d4c2c89dc1..cc880a3d08 100644
--- a/hw/net/xilinx_axienet.c
+++ b/hw/net/xilinx_axienet.c
@@ -951,12 +951,12 @@ static void xilinx_enet_realize(DeviceState *dev, Error **errp)
     object_property_add_link(OBJECT(ds), "enet", "xlnx.axi-ethernet",
                              (Object **) &ds->enet,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              &local_err);
     object_property_add_link(OBJECT(cs), "enet", "xlnx.axi-ethernet",
                              (Object **) &cs->enet,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              &local_err);
     if (local_err) {
         goto xilinx_enet_realize_fail;
diff --git a/hw/ssi/xilinx_spips.c b/hw/ssi/xilinx_spips.c
index 03f5faee4b..f599025956 100644
--- a/hw/ssi/xilinx_spips.c
+++ b/hw/ssi/xilinx_spips.c
@@ -1346,7 +1346,7 @@ static void xlnx_zynqmp_qspips_init(Object *obj)
     object_property_add_link(obj, "stream-connected-dma", TYPE_STREAM_SLAVE,
                              (Object **)&rq->dma,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              NULL);
 }
 
diff --git a/net/can/can_host.c b/net/can/can_host.c
index c3d26521cd..c79347abab 100644
--- a/net/can/can_host.c
+++ b/net/can/can_host.c
@@ -77,7 +77,7 @@ static void can_host_instance_init(Object *obj)
     object_property_add_link(obj, "canbus", TYPE_CAN_BUS,
                              (Object **)&ch->bus,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              &error_abort);
 }
 
diff --git a/net/colo-compare.c b/net/colo-compare.c
index 23b2d2c4cc..63469b11a1 100644
--- a/net/colo-compare.c
+++ b/net/colo-compare.c
@@ -980,7 +980,7 @@ static void colo_compare_init(Object *obj)
     object_property_add_link(obj, "iothread", TYPE_IOTHREAD,
                             (Object **)&s->iothread,
                             object_property_allow_set_link,
-                            OBJ_PROP_LINK_UNREF_ON_RELEASE, NULL);
+                            OBJ_PROP_LINK_STRONG, NULL);
 
     s->vnet_hdr = false;
     object_property_add_bool(obj, "vnet_hdr_support", compare_get_vnet_hdr,
diff --git a/qom/object.c b/qom/object.c
index 0fc972030e..bfec376628 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -1564,9 +1564,11 @@ static void object_set_link_property(Object *obj, Visitor *v,
         return;
     }
 
-    object_ref(new_target);
     *child = new_target;
-    object_unref(old_target);
+    if (prop->flags == OBJ_PROP_LINK_STRONG) {
+        object_ref(new_target);
+        object_unref(old_target);
+    }
 }
 
 static Object *object_resolve_link_property(Object *parent, void *opaque, const gchar *part)
@@ -1581,7 +1583,7 @@ static void object_release_link_property(Object *obj, const char *name,
 {
     LinkProperty *prop = opaque;
 
-    if ((prop->flags & OBJ_PROP_LINK_UNREF_ON_RELEASE) && *prop->child) {
+    if ((prop->flags & OBJ_PROP_LINK_STRONG) && *prop->child) {
         object_unref(*prop->child);
     }
     g_free(prop);
diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 5d60893a07..ab047b9402 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -690,7 +690,7 @@ static void arm_cpu_post_init(Object *obj)
                                  TYPE_MEMORY_REGION,
                                  (Object **)&cpu->secure_memory,
                                  qdev_prop_allow_set_link_before_realize,
-                                 OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                                 OBJ_PROP_LINK_STRONG,
                                  &error_abort);
 #endif
     }
@@ -718,7 +718,7 @@ static void arm_cpu_post_init(Object *obj)
     if (arm_feature(&cpu->env, ARM_FEATURE_M_SECURITY)) {
         object_property_add_link(obj, "idau", TYPE_IDAU_INTERFACE, &cpu->idau,
                                  qdev_prop_allow_set_link_before_realize,
-                                 OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                                 OBJ_PROP_LINK_STRONG,
                                  &error_abort);
         qdev_property_add_static(DEVICE(obj), &arm_cpu_initsvtor_property,
                                  &error_abort);
diff --git a/ui/console.c b/ui/console.c
index ef1247f872..bc58458ee8 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -1287,7 +1287,7 @@ static QemuConsole *new_console(DisplayState *ds, console_type_t console_type,
     object_property_add_link(obj, "device", TYPE_DEVICE,
                              (Object **)&s->device,
                              object_property_allow_set_link,
-                             OBJ_PROP_LINK_UNREF_ON_RELEASE,
+                             OBJ_PROP_LINK_STRONG,
                              &error_abort);
     object_property_add_uint32_ptr(obj, "head",
                                    &s->head, &error_abort);
-- 
2.17.1.906.g10fd178552

[Qemu-devel] [PATCH 3/4] usb-ccid: fix bus leak

[Marc-André Lureau]

qbus_create_inplace() creates a new reference in realize(), it must be
released in unrealize().

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 hw/usb/dev-smartcard-reader.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/hw/usb/dev-smartcard-reader.c b/hw/usb/dev-smartcard-reader.c
index f7451923f4..a564d24d7e 100644
--- a/hw/usb/dev-smartcard-reader.c
+++ b/hw/usb/dev-smartcard-reader.c
@@ -1147,6 +1147,7 @@ static void ccid_unrealize(USBDevice *dev, Error **errp)
     USBCCIDState *s = USB_CCID_DEV(dev);
 
     ccid_bulk_in_clear(s);
+    object_unref(OBJECT(&s->bus));
 }
 
 static void ccid_flush_pending_answers(USBCCIDState *s)
-- 
2.17.1.906.g10fd178552

[Qemu-devel] [PATCH 4/4] usb-hcd-xhci-test: add a test for ccid hotplug

[Marc-André Lureau]

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 tests/usb-hcd-xhci-test.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tests/usb-hcd-xhci-test.c b/tests/usb-hcd-xhci-test.c
index 9c14e3053a..5b1b681bf2 100644
--- a/tests/usb-hcd-xhci-test.c
+++ b/tests/usb-hcd-xhci-test.c
@@ -35,6 +35,15 @@ static void test_usb_uas_hotplug(void)
     qtest_qmp_device_del("uas");
 }
 
+static void test_usb_ccid_hotplug(void)
+{
+    qtest_qmp_device_add("usb-ccid", "ccid", NULL);
+    qtest_qmp_device_del("ccid");
+    /* check the device can be added again */
+    qtest_qmp_device_add("usb-ccid", "ccid", NULL);
+    qtest_qmp_device_del("ccid");
+}
+
 int main(int argc, char **argv)
 {
     int ret;
@@ -44,6 +53,7 @@ int main(int argc, char **argv)
     qtest_add_func("/xhci/pci/init", test_xhci_init);
     qtest_add_func("/xhci/pci/hotplug", test_xhci_hotplug);
     qtest_add_func("/xhci/pci/hotplug/usb-uas", test_usb_uas_hotplug);
+    qtest_add_func("/xhci/pci/hotplug/usb-ccid", test_usb_ccid_hotplug);
 
     qtest_start("-device nec-usb-xhci,id=xhci"
                 " -drive id=drive0,if=none,file=null-co://,format=raw");
-- 
2.17.1.906.g10fd178552

Re: [Qemu-devel] [PATCH 0/4] Fix usb-ccid hotplug regression

[Paolo Bonzini]

On 31/05/2018 21:51, Marc-André Lureau wrote:
> Hi,
> 
> The following series fixes the usb-ccid hotplug regression introduced
> by commit 675f22c6d3b0: the plugged device is not completely removed
> on device_del anymore, due to an extra reference added when doing
> set_link(). It turns out the memory management of qdev bus/child is a
> bit weird, this is my attempt to improve the situation and fix the
> regression.

It's my fault for not reviewing this promptly, but can patches 1 and 3
please be reverted?  Thanks,

Paolo

> Fixes:
> https://bugzilla.redhat.com/show_bug.cgi?id=1556678
> 
> Marc-André Lureau (4):
>   bus: do not unref the added child bus on realize
>   object: fix OBJ_PROP_LINK_UNREF_ON_RELEASE ambivalence
>   usb-ccid: fix bus leak
>   usb-hcd-xhci-test: add a test for ccid hotplug
> 
>  include/qom/object.h          | 12 +++++++++---
>  hw/core/bus.c                 |  1 -
>  hw/core/qdev-properties.c     |  2 +-
>  hw/core/qdev.c                |  2 +-
>  hw/display/xlnx_dp.c          |  2 +-
>  hw/dma/xilinx_axidma.c        |  4 ++--
>  hw/dma/xlnx-zdma.c            |  2 +-
>  hw/i386/pc.c                  |  2 +-
>  hw/i386/pc_piix.c             |  2 +-
>  hw/i386/pc_q35.c              |  2 +-
>  hw/ipmi/ipmi.c                |  2 +-
>  hw/net/xilinx_axienet.c       |  4 ++--
>  hw/ssi/xilinx_spips.c         |  2 +-
>  hw/usb/dev-smartcard-reader.c |  1 +
>  net/can/can_host.c            |  2 +-
>  net/colo-compare.c            |  2 +-
>  qom/object.c                  |  8 +++++---
>  target/arm/cpu.c              |  4 ++--
>  tests/usb-hcd-xhci-test.c     | 10 ++++++++++
>  ui/console.c                  |  2 +-
>  20 files changed, 43 insertions(+), 25 deletions(-)
> 
> 
> base-commit: c181ddaa176856b3cd2dfd12bbcf25fa9c884a97
> 

Re: [Qemu-devel] [PATCH 0/4] Fix usb-ccid hotplug regression

[Gerd Hoffmann]

On Wed, Jun 13, 2018 at 06:18:19PM +0200, Paolo Bonzini wrote:
> On 31/05/2018 21:51, Marc-André Lureau wrote:
> > Hi,
> > 
> > The following series fixes the usb-ccid hotplug regression introduced
> > by commit 675f22c6d3b0: the plugged device is not completely removed
> > on device_del anymore, due to an extra reference added when doing
> > set_link(). It turns out the memory management of qdev bus/child is a
> > bit weird, this is my attempt to improve the situation and fix the
> > regression.
> 
> It's my fault for not reviewing this promptly, but can patches 1 and 3
> please be reverted?  Thanks,

Can you have a look at the revert series posted by Marc?

thanks,
  Gerd