[PD-dev] Is gensym() threadsafe?

[Kjetil S. Matheussen]

How about changing sys_lock to something like this:

void sys_lock(){
    if(pd_is_running_realtime() && caller_is_not_running_realtime()){
       post("Error! You must run your thread with realtime priority to be allowed to call sys_lock. Period!");
       abort();
    }
    ...
}


On Tue, 13 Dec 2005, Thomas Grill wrote:

> 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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>
>