Re: [Xenomai-help] :: rt_printf with daemonized task

[Jan Kiszka <jan.kiszka@domain.hid>]

oliver.schlenker@domain.hid wrote:
> 
> 
> 
> 
> -------- Original Message --------
> Subject: Re: Re : rt_printf with daemonized task (08-Okt-2009 12:16)
> From:    Jan Kiszka <jan.kiszka@domain.hid>
> To:      oliver.schlenker@domain.hid
> 
>> Gilles Chanteperdrix wrote:
>>> Jan Kiszka wrote:
>>>> Gilles Chanteperdrix wrote:
>>>>> oliver.schlenker@domain.hid wrote:
>>>>>>>> int main( int arc, char *argv[] ) { int i;
>>>>>>>>
>>>>>>>> rt_print_auto_init(1);
>>>>>>>>
>>>>>>>> rt_printf("--------------- TEST RT-PRINTF  1 ------------\n");
>>>>>>>>
>>>>>>>> sleep(1);
>>>>>>>>
>>>>>>>> daemon(0,0);
>>>>>>>>
>>>>>>>> rt_print_auto_init(1);
>>>>>> Ok, understood, at least for the scenario where the rt_print feature
>>>>>> is initialised befor the fork/daemon call. What I don't understand
>>>>>> is, why it does not work if the rt_print feature is initialised after
>>>>>> the fork / daemon.
>>>>> From the way I understand your code, you never tried to initialize the
>>>>> rt_print feature only after the fork, your code initializes it both
>>>>> before and after.
>>>>>
>>>> There are two initializations: The base init done via __rt_print_init on
>>>> library loading and the one to be done per-thread via rt_print_init (or
>>>> on first rt_printf). That printer thread is initialized via the former
>>>> one. On fork, we do not need to re-run the full __rt_print_init
>>>> (variables and resources are cloned on fork), we just need to spawn
>>>> another printer thread.
>>> Unless I am wrong, rtdk also maintains a list of the thread buffers
>>> which need to be polled. After the fork, this list will be intact, but
>>> the threads to which belong the buffers will no longer exist. So, IMO,
>>> the fork handler should also free all these buffers and reset the list
>>> to the empty state.
>> Famous last words: That should work without tweaking. A print_buffer
>> only contains data references, nothing that points to some uncloned thread.
>>
>> Jan
>>
>> -- 
>> Siemens AG, Corporate Technology, CT SE 2
>> Corporate Competence Center Embedded Linux
> 
> To have a fork save rtprint library it's necessary to
> 
> 1. Reset rtdk thread buffer list
>    
>     I have no idea where to look at for the rtdk thread buffer list. Inside rt_print.c ?

It's all there, it's called first_buffer. Just walk that list and call
cleanup_buffers on the entries.

>    
> 2. Spawning another printer thread
>     with code like :
> 	pthread_attr_init(&thattr);
> 	pthread_attr_setstacksize(&thattr, PTHREAD_STACK_MIN);
> 	pthread_create(&__printer_thread, &thattr, printer_loop, NULL); 
> 
> 
> Is there anything else to do ?
> 

Probably not, but I was already wrong before. :)

> 
> I'm also planning to add a function to the lib like :
> 
> rt_print_to_syslog( int priority )

Better provide some rt_syslog(int priority, char *format, ...),
corresponding to the standard service.

Jan

-- 
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux