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

[Wen Congyang <wency@xxxxxxxxxxxxxx>]

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.

> 
> 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.

Thanks
Wen Congyang

> 
>> +        else
>> +            write_emulator_xenstore_record(egc, stream);
>> +    }
>>  }
>>  
>>  static void write_emulator_xenstore_record(libxl__egc *egc,
> 
> 
> .
> 




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