Re: [Xen-devel] [PATCH v11 12/27] tools/libx{l, c}: introduce wait_checkpoint callback

[Wen Congyang <wency@xxxxxxxxxxxxxx>]

On 03/05/2016 04:23 AM, Konrad Rzeszutek Wilk wrote:
> On Fri, Mar 04, 2016 at 05:03:16PM +0000, Ian Jackson wrote:
>> Changlong Xie writes ("[PATCH v11 12/27] tools/libx{l,c}: introduce 
>> wait_checkpoint callback"):
>>> From: Wen Congyang <wency@xxxxxxxxxxxxxx>
>>>
>>> Under COLO, we are doing checkpoint on demand, if this
>>> callback returns 1, we will take another checkpoint.
>>> 0 indicates unexpected error.
>>
>> This doesn't seem to have a corresponding implementation.  I think the
>> implementation ought to be in the same patch.
>>
>> If 0 is always an `unexpected error', perhaps the return value should
>> be an error code or something ?  I'm not sure.
> 
> I struggled with this API.
> 
> I like the idea of that negative value would imply 'unexpected error'.
> And 1 for 'OK, take another checkpoint'. Not sure if zero would be a valid
> return value..

IIRC, save/restore callback always use 0 for unexpected error, 1 for OK.
negative value for pipe is broken.

Thanks
Wen Congyang

> 
> 
>>
>> Ian.
> 
> 
> .
> 




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