Re: [LAD] some questions about writing a jack client

On Wed, 25 Nov 2009, Paul Davis wrote:

> On Wed, Nov 25, 2009 at 12:10 PM, Kjetil S. Matheussen
> <k.s.matheussen@email-addr-hidden> wrote:
>>
>> "Gabriel M. Beddingfield":
>>> So you see, by using a mutex... you have to consider
>>> those sections of code as being a part of your
>>> process() function.
>>
>> Great explanation, but you forgot to explicitly mention
>> that those sections of code also has to run with higher
>> or equal priority as the jack process to avoid priority
>> inversion.
>
> and since (IIRC) linux/pthreads don't do this, you basically should
> never use a lock in this fashion at all!
>
> pthread_mutex_trylock() is fine. just avoid pthread_mutex_lock(). this
> does require that you have some fallback strategy: what to do if you
> can't take the lock.
>

But sometimes it makes sense to temporarily boost performance
of non-realtime threads, like this:

non_realtime_thread_visiting(){
   old_prio = get_prio();
   set_prio(jack_prio);{
     pthread_mutex_lock(){
       <do realtime-safe stuff>
     }pthread_mutex_unlock();
   }set_prio(old_prio)
}

jack_process_thread(){
   pthread_mutex_lock(){
     <do realtime-safe stuff>
   }pthread_mutex_unlock();
}

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Received on Thu Nov 26 00:15:03 2009