Re: [Xen-devel] [PATCH v3 04/11] libxl: add generic function to add device

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Jun 27, 2017 at 01:03:20PM +0300, Oleksandr Grytsov wrote:
> From: Oleksandr Grytsov <oleksandr_grytsov@xxxxxxxx>
> 
> Add libxl__device_add functio.
> Almost all devices have similar libxl__device_xxxx_add function.
> This generic function implements same functionality but
> using the device handling framework. The device specific
> part this is setting xen store configuration. This part
> is moved to set_xenstore_config callback of the device framework.
> 
> Signed-off-by: Oleksandr Grytsov <oleksandr_grytsov@xxxxxxxx>
[...]
> +
> +void libxl__device_add(libxl__egc *egc, uint32_t domid,
> +                       const struct libxl_device_type *dt, void *type,
> +                       libxl__ao_device *aodev)
> +{
> +    STATE_AO_GC(aodev->ao);
> +    libxl__device *device;
> +    int rc;
> +
> +    rc = dt->set_default(gc, domid, type);
> +    if (rc) goto out;
> +
> +    GCNEW(device);
> +    rc = dt->to_device(gc, domid, type, device);
> +    if ( rc != 0 ) goto out;
> +
> +    rc = libxl__device_exists(gc, XBT_NULL, device);
> +    if (rc < 0) goto out;
> +    if (rc == 1) {              /* already exists in xenstore */
> +        LOGD(ERROR, domid, "device already exists in xenstore");
> +        aodev->action = LIBXL__DEVICE_ACTION_ADD; /* for error message */
> +        rc = ERROR_DEVICE_EXISTS;
> +        goto out;
> +    }
> +
> +    if (aodev->update_json) {
> +        rc = device_add_domain_config(gc, domid, dt, type);
> +        if (rc) goto out;
> +    }
> +
> +    if (dt->set_xenstore_config) {
> +        rc = dt->set_xenstore_config(gc, domid, type);
> +        if (rc) goto out;
> +    }
> +

This has changed the locking hierarchy we define in libxl_internal.h.
See libxl_internal.h:L2592.

Either you need to preserve the hierarchy or you need to prove the
correctness of the new approach. The former is probably easier.

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