[Devel] Re: [RFC PATCH 11/17] define function to print error messages to user log

[Oren Laadan]

Serge E. Hallyn wrote:
> Quoting Oren Laadan (orenl at librato.com):
>>
>> Serge E. Hallyn wrote:
>>> Quoting Oren Laadan (orenl at librato.com):
>>>> Serge E. Hallyn wrote:
>>>>> Quoting Oren Laadan (orenl at librato.com):
>>>>>> Serge E. Hallyn wrote:
>>>>>>> Quoting Matt Helsley (matthltc at us.ibm.com):
>>>>>>>>> @@ -401,6 +409,9 @@ char *ckpt_generate_fmt(struct ckpt_ctx *ctx, char *fmt)
>>>>>>>>>  		case 'E':
>>>>>>>>>  			len += sprintf(format+len, "[%s]", "err %d");
>>>>>>>>>  			break;
>>>>>>>>> +		case 'C': /* count of bytes read/written to checkpoint image */
>>>>>>>>> +			len += sprintf(format+len, "[%s]", "pos %d");
>>>>>>>>> +			break;
>>>>>>>> Instead we could always output ckpt->total and then we wouldn't need %(C). I
>>>>>>>> suspect it's such a useful piece of information that it'll be repeated
>>>>>>>> in many/all format strings eventually.
>>>>>>> Yes, likewise %(T).  If that's what we want to do.
>>>>>> I agree. For the cases when there is not task, can put "none"
>>>>>>
>>>>>>> Should we discuss here what we want an entry to look like?  For both
>>>>>>> ckpt_write_err (to the checkpoint image) and ckpt_error()?
>>>>>>>
>>>>>> Yes please !
>>>>> Actually %T isn't the current task, right, so it shouldn't always be prepended?
>>>>> It actually is only meaningful during checkpoint_task(), collect_objs(), and
>>>>> __tree_count_tasks?
>>>>>
>>>>> Ok, so how about:
>>>>>
>>>>> 	1. ckpt_write_err() always also calls ckpt_error() (which in turn calls
>>>>> 		ckpt_debug).  Avoid duplication which exists in several places
>>>>> 		right now.
>>>>> 	2. We always prepend:
>>>>>
>>>>> 		[current->pid]:[ctx->root_pid]:[ctx->active_pid]:[ctx->errno][ctx->total]
>>>>>
>>>>> 	The %(X) expansions if specified come whereever they are in the fmt
>>>>> 	string (which is what's happening now with my patchset).
>>>> So somewhere should set ctx->errno during a checkpoint.
>>>>
>>>> I suppose active_pid is for restart, but it's redundant isn't it ?
>>>> (it's always active_pid) - is it the different between top-level pid-ns
>>>> and "current" pid-ns ?
>>> No, I figured it would be meaningful for instance in places like
>>> wait_task_active().
>> Perhaps then leave it out of the default printing, and have the
>> specific debug messages there write it explicitly.
> 
> Ok, so then current suggested format looks like:
> 
> [current->pid]:[ctx->errno]:[ctx->total]
> 
> Though is ctx->errno helpful even in restart?  Or should we assume we'll
> figure that out through the msg in restore_notify_error()?
> 
> Maybe do:
> [current->pid]=[task_pid_vnr(current)]:[ctx->total]

I think errno is only helpful if an error occured.

So it should definitely be a part of the default msg given by
ckpt_error(), but not otherwise.

Oren.

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