Re: [Qemu-arm] [Qemu-devel] [PATCH v2 15/16] hw/arm/mps2: Use object_initialize_child for correct reference counting

[Paolo Bonzini]

On 07/05/19 11:34, Philippe Mathieu-Daudé wrote:
> As explained in commit aff39be0ed97:
> 
>   Both functions, object_initialize() and object_property_add_child()
>   increase the reference counter of the new object, so one of the
>   references has to be dropped afterwards to get the reference
>   counting right. Otherwise the child object will not be properly
>   cleaned up when the parent gets destroyed.
>   Thus let's use now object_initialize_child() instead to get the
>   reference counting here right.
> 
> This patch was generated using the following Coccinelle script:
> 
>  @use_sysbus_init_child_obj_missing_parent@
>  expression child_ptr;
>  expression child_type;
>  expression child_size;
>  @@
>  -   object_initialize(child_ptr, child_size, child_type);
>      ...
>  -   qdev_set_parent_bus(DEVICE(child_ptr), sysbus_get_default());
>      ...
>  ?-  object_unref(OBJECT(child_ptr));
>  +   sysbus_init_child_obj(OBJECT(PARENT_OBJ), "CHILD_NAME", child_ptr,
>  +                         child_size, child_type);
> 
> We let the MPS2 boards adopt the cpu core, the FPGA and the SCC children.
> 
> While the object_initialize() function doesn't take an
> 'Error *errp' argument, the object_initialize_child() does.
> Since this code is used when a machine is created (and is not
> yet running), we deliberately choose to use the &error_abort
> argument instead of ignoring errors if an object creation failed.
> This choice also matches when using sysbus_init_child_obj(),
> since its code is:
> 
>   void sysbus_init_child_obj(Object *parent,
>                              const char *childname, void *child,
>                              size_t childsize, const char *childtype)
>   {
>       object_initialize_child(parent, childname, child, childsize,
>                               childtype, &error_abort, NULL);
> 
>       qdev_set_parent_bus(DEVICE(child), sysbus_get_default());
>   }
> 
> Suggested-by: Eduardo Habkost <address@hidden>
> Inspired-by: Thomas Huth <address@hidden>
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> ---
>  hw/arm/mps2-tz.c | 8 ++++----
>  hw/arm/mps2.c    | 8 ++++----
>  2 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/hw/arm/mps2-tz.c b/hw/arm/mps2-tz.c
> index 7832408bb70..82dce1a7b38 100644
> --- a/hw/arm/mps2-tz.c
> +++ b/hw/arm/mps2-tz.c
> @@ -214,9 +214,9 @@ static MemoryRegion *make_scc(MPS2TZMachineState *mms, 
> void *opaque,
>      DeviceState *sccdev;
>      MPS2TZMachineClass *mmc = MPS2TZ_MACHINE_GET_CLASS(mms);
>  
> -    object_initialize(scc, sizeof(mms->scc), TYPE_MPS2_SCC);
> +    sysbus_init_child_obj(OBJECT(mms), "scc", scc,
> +                          sizeof(mms->scc), TYPE_MPS2_SCC);
>      sccdev = DEVICE(scc);
> -    qdev_set_parent_bus(sccdev, sysbus_get_default());
>      qdev_prop_set_uint32(sccdev, "scc-cfg4", 0x2);
>      qdev_prop_set_uint32(sccdev, "scc-aid", 0x00200008);
>      qdev_prop_set_uint32(sccdev, "scc-id", mmc->scc_id);
> @@ -229,8 +229,8 @@ static MemoryRegion *make_fpgaio(MPS2TZMachineState *mms, 
> void *opaque,
>  {
>      MPS2FPGAIO *fpgaio = opaque;
>  
> -    object_initialize(fpgaio, sizeof(mms->fpgaio), TYPE_MPS2_FPGAIO);
> -    qdev_set_parent_bus(DEVICE(fpgaio), sysbus_get_default());
> +    sysbus_init_child_obj(OBJECT(mms), "fpgaio", fpgaio,
> +                          sizeof(mms->fpgaio), TYPE_MPS2_FPGAIO);
>      object_property_set_bool(OBJECT(fpgaio), true, "realized", &error_fatal);
>      return sysbus_mmio_get_region(SYS_BUS_DEVICE(fpgaio), 0);
>  }
> diff --git a/hw/arm/mps2.c b/hw/arm/mps2.c
> index 54b7395849f..ecb8ae3c14c 100644
> --- a/hw/arm/mps2.c
> +++ b/hw/arm/mps2.c
> @@ -174,9 +174,9 @@ static void mps2_common_init(MachineState *machine)
>          g_assert_not_reached();
>      }
>  
> -    object_initialize(&mms->armv7m, sizeof(mms->armv7m), TYPE_ARMV7M);
> +    sysbus_init_child_obj(OBJECT(mms), "armv7m", &mms->armv7m,
> +                          sizeof(mms->armv7m), TYPE_ARMV7M);
>      armv7m = DEVICE(&mms->armv7m);
> -    qdev_set_parent_bus(armv7m, sysbus_get_default());
>      switch (mmc->fpga_type) {
>      case FPGA_AN385:
>          qdev_prop_set_uint32(armv7m, "num-irq", 32);
> @@ -308,9 +308,9 @@ static void mps2_common_init(MachineState *machine)
>                         qdev_get_gpio_in(armv7m, 10));
>      sysbus_mmio_map(SYS_BUS_DEVICE(&mms->dualtimer), 0, 0x40002000);
>  
> -    object_initialize(&mms->scc, sizeof(mms->scc), TYPE_MPS2_SCC);
> +    sysbus_init_child_obj(OBJECT(mms), "scc", &mms->scc,
> +                          sizeof(mms->scc), TYPE_MPS2_SCC);
>      sccdev = DEVICE(&mms->scc);
> -    qdev_set_parent_bus(sccdev, sysbus_get_default());
>      qdev_prop_set_uint32(sccdev, "scc-cfg4", 0x2);
>      qdev_prop_set_uint32(sccdev, "scc-aid", 0x00200008);
>      qdev_prop_set_uint32(sccdev, "scc-id", mmc->scc_id);
> 

Reviewed-by: Paolo Bonzini <address@hidden>