Re: [Qemu-devel] [PATCH 06/11] pseries: Improve error handling in find_unknown_sysbus_device()

[Eric Blake <eblake@redhat.com>]

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On 12/10/2015 05:11 PM, David Gibson wrote:
> Use error_setg() to return an error instead of using an explicit exit().
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  hw/ppc/spapr.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 

> +++ b/hw/ppc/spapr.c
> @@ -1107,6 +1107,7 @@ static void spapr_reset_htab(sPAPRMachineState *spapr, Error **errp)
>  
>  static int find_unknown_sysbus_device(SysBusDevice *sbdev, void *opaque)
>  {

>      if (!matched) {
> -        error_report("Device %s is not supported by this machine yet.",
> -                     qdev_fw_name(DEVICE(sbdev)));
> -        exit(1);
> +        error_setg(errp,
> +                   "Device %s is not supported by this machine yet",
> +                   qdev_fw_name(DEVICE(sbdev)));
>      }
>  
>      return 0;

It looks like find_unknown_sysbus_device is designed to be called in a
loop, and that returning 0 lets the loop continue.

> @@ -1151,7 +1152,7 @@ static void ppc_spapr_reset(void)
>      uint32_t rtas_limit;
>  
>      /* Check for unknown sysbus devices */
> -    foreach_dynamic_sysbus_device(find_unknown_sysbus_device, NULL);
> +    foreach_dynamic_sysbus_device(find_unknown_sysbus_device, &error_abort);

If a caller passes something other than &error_abort as the opaque, AND
the error condition occurs more than once in the loop iteration, then
you really need to change find_unknown_sysbus_device() to return
non-zero after raising error on the first failure, so that the loop
doesn't continue on to a second pass and attempt an error_setg() onto an
already-set error.

Of course, since _this_ patch uses &error_abort as the only client, the
loop will never continue after the first failure, but it's more robust
to be clean without having to audit the callers.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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