[PD-dev] Is gensym() threadsafe?

[Thomas Grill]

Hi Kjetil,
to my mind using syslock is dangerous in any case, because if the lock 
is held by someone else you might wait up to 1 ms (depending on your OS 
turnaround frequency) at this point.
Of course it depends on how often you use gensym, but i would avoid 
it.... (although i introduced it... my bad)

greetings,
Thomas


Am 13.12.2005 um 23:04 schrieb Kjetil S. Matheussen:

> On Tue, 13 Dec 2005, Kjetil S. Matheussen wrote:
>
>> On Tue, 13 Dec 2005, Kjetil S. Matheussen wrote:
>>
>>> On Tue, 13 Dec 2005, Tim Blechmann wrote:
>>>> hi kjetil,
>>>>> I'm working on the snd external, and wonder about gensyms thread
>>>>> safety. It looks to be, but I'm not quite sure. In case it isn't
>>>>> is there a locking-mechanism or something I can use?
>>>>> I also see that there are some functions called sys_lock or
>>>>> something, how does they work?
>>>> gensym is basically not thread safe ... for the devel branch i made
>>>> gensym threadsafe, but if you want to write code for miller's pd, 
>>>> you
>>>> need to use the syslock ...
>>> Thanks! So how do I use syslock from another thread?
>>> Does this make sence:?
>>> t_symbol *thread_safe_gensym(char *symbol){
>>> t_symbol *ret;
>>> sys_lock();
>>> ret=gensym(symbol);
>>> sys_unlock();
>>> return ret;
>>> }
>>
>> Hm, no, actually, I can't do that. Snd isn't running with realtime 
>> priority, so if pd needs to wait for snd, pd will in practice lose 
>> its realtime priority when it has to wait for Snd.
>> Miller P.: Please apply Tim's threadsafe gensym to your version. :-)
>>
>
> Oops, of course, I can just do it like this:
>
> t_symbol *thread_safe_gensym(char *symbol){
>   t_symbol *ret;
>   struct sched_param par;
>   par.sched_priority = sched_get_priority_max(SCHED_FIFO);
>   sched_setscheduler(0,SCHED_FIFO,&par);
>   sys_lock();
>   ret=gensym(symbol);
>   sys_unlock();
>   sched_setscheduler(0,SCHED_OTHER,&par);
>   return ret;
> }
>
>
> -- 
>
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