On Fri, Dec 18, 2015 at 04:30:47PM +0100, Igor Mammedov wrote:
> qdev_device_add() currently uses object_new() which
> will abort if there memory allocation for device instance
> fails. While it's fine it startup, it is not desirable
> diring hotplug.
>
> Try to allocate memory for object first and fail safely
> if allocation fails.
>
> Signed-off-by: Igor Mammedov <imamm...@redhat.com>
> ---
> It's just a step in making hotplug safer wrt object allocation.
> To make it more safer, hotplugged class constructor
> shouldn't allocate memory either, but that should be
> addressed on per device basis providing we fix QOM
> internals to avoid dynamic allocations.
> ---
> qdev-monitor.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/qdev-monitor.c b/qdev-monitor.c
> index a35098f..a70262e 100644
> --- a/qdev-monitor.c
> +++ b/qdev-monitor.c
> @@ -514,6 +514,7 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error **errp)
> DeviceClass *dc;
> const char *driver, *path, *id;
> DeviceState *dev;
> + size_t obj_size;
> BusState *bus = NULL;
> Error *err = NULL;
>
> @@ -555,7 +556,13 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error
> **errp)
> }
>
> /* create device */
> - dev = DEVICE(object_new(driver));
> + obj_size = object_class_get_instance_size(OBJECT_CLASS(dc));
> + dev = g_try_malloc0(obj_size);
> + if (dev == NULL) {
> + error_setg(errp, "Not enough memory for Device '%s'", driver);
> + return NULL;
> + }
This just avoids one small malloc failure.
> + object_initialize(dev, obj_size, driver);
This is going to call g_new many more times, so you'll
still hit OOM almost immediately. eg the call to
g_hash_table_new_full() in object_initialize_with_type
will abort on OOM, not to mention anything run in a
instance constructor function registered against the
class. There's no way to avoid this given that we have
chosen to use GLib in QEMU, so I don't really see any
point in replacing the 'object_new' call with g_try_malloc
Regards,
Daniel
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