Re: [Xen-devel] [PATCH v3 2/5] remus: resume immediately if libxl__xc_domain_save_done() completes

[Wen Congyang <wency@xxxxxxxxxxxxxx>]

On 01/15/2016 05:48 PM, Ian Campbell wrote:
> On Fri, 2016-01-15 at 13:44 +0800, Wen Congyang wrote:
>> On 01/14/2016 06:21 PM, Ian Campbell wrote:
>>> On Tue, 2016-01-12 at 09:40 +0800, Wen Congyang wrote:
>>>> On 01/09/2016 12:27 AM, Ian Campbell wrote:
>>>>> On Fri, 2016-01-08 at 14:38 +0800, Wen Congyang wrote:
>>>>>> For example: if the secondary host is down, and we fail to send
>>>>>> the
>>>>>> data
>>>>>> to
>>>>>> the secondary host. xc_domain_save() returns 0.
>>>>>
>>>>> Just to be check: On failure in this way xc_domain_save() returns 0
>>>>> (i.e.
>>>>> success)?
>>>>
>>>> Yes, it returns 0. I am not sure the return value is right.
>>>>
>>>>>
>>>>>>  So in the function
>>>>>> libxl__xc_domain_save_done(), rc is 0(the helper program exits
>>>>>> normally),
>>>>>> and retval is 0(it is xc_domain_save()'s return value). In such
>>>>>> case,
>>>>>> we
>>>>>> just need to complete the stream.
>>>>>>
>>>>>> Signed-off-by: Wen Congyang <wency@xxxxxxxxxxxxxx>
>>>>>> ---
>>>>>>  tools/libxl/libxl_stream_write.c | 13 +++++++++++--
>>>>>>  1 file changed, 11 insertions(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/tools/libxl/libxl_stream_write.c
>>>>>> b/tools/libxl/libxl_stream_write.c
>>>>>> index 80d9208..82e7719 100644
>>>>>> --- a/tools/libxl/libxl_stream_write.c
>>>>>> +++ b/tools/libxl/libxl_stream_write.c
>>>>>> @@ -354,8 +354,17 @@ void libxl__xc_domain_save_done(libxl__egc
>>>>>> *egc,
>>>>>> void *dss_void,
>>>>>>       * alive, and check_all_finished() may have torn it down
>>>>>> around
>>>>>> us.
>>>>>>       * If the stream is not still alive, we must not continue
>>>>>> any
>>>>>> work.
>>>>>>       */
>>>>>> -    if (libxl__stream_write_inuse(stream))
>>>>>> -        write_emulator_xenstore_record(egc, stream);
>>>>>> +    if (libxl__stream_write_inuse(stream)) {
>>>>>> +        if (dss->remus)
>>>>>> +            /*
>>>>>> +             * For remus, if libxl__xc_domain_save_done()
>>>>>> completes,
>>>>>> +             * there was an error sending data to the secondary.
>>>>>> +             * Resume the primary ASAP.
>>>>>> +             */
>>>>>> +            stream_complete(egc, stream, 0);
>>>>>
>>>>> Is there an indication to the caller that things have failed in
>>>>> this
>>>>> way?
>>>>> Would that information be of use to the caller?
>>>>
>>>> For remus, when we come here, something is wrong regardless of the
>>>> return
>>>> value.
>>>
>>> But does the caller know this? Can it tell.
>>>
>>>>
>>>>>
>>>>> Or does the called infer this has happened because
>>>>> otherwise libxl_domain_remus_start is not supposed to return?
>>>>
>>>> Yes, libxl_domain_remus_start() should not return unless somethins is
>>>> wrong.
>>>
>>> This really ought to be documented somewhere.
>>
>> libxl_domain_remus_start():
>>     /* Point of no return */
>>     libxl__remus_setup(egc, dss);
>>     return AO_INPROGRESS;
> 
> This is (obviously) not documentation.

OK, I will update the comment.

Thanks
Wen Congyang

> 
> 
> 
> .
> 




_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel