[PD] lock free problem

[Marco Matteo Markidis]

So, for a complete guaranteed situation a [readsf~]-like mechanics is a
good solution?
"Generate Pd messages from outside the main thread" means to generate
something in Pd, i.e. with a multithreaded externals, but from a child
thread?

Best,

Marco

2016-08-23 18:54 GMT+02:00 Miller Puckette <msp at ucsd.edu>:

> Well, Pd itself only calls that lock from its main thread - so
> theoretically
> that call won't ever block.  But it's provided in case someone wants to
> generate Pd messages from outside the main thread.  If you do that, Pd's
> call to the lock can block - whether the time it's blocked can be bounded
> depends on the behavior of  the other thread and the OS's ability to give
> control quickly to a blocked thread when another thread releases the lock.
> It's probably very hard to guarantee but probably works 99% of the time in
> reasonable situations.
>
> cheers
> Miller
>
> On Tue, Aug 23, 2016 at 06:26:16PM +0200, Marco Matteo Markidis wrote:
> > Thank you Miller for your answer.
> >
> > This afternoon I just took a look of s_audio_paring.c/h.
> > Do you think the lock in the scheduler can be a problem? It's meaningful
> a
> > lock free queue between audio and worker thread?
> >
> > Best,
> > Marco
> >
> > 2016-08-23 18:13 GMT+02:00 Miller Puckette <msp at ucsd.edu>:
> >
> > > There's a good, byte-stream lock-free fifo in pd/src/s_audio_paring.c .
> > > (It's borrowed from portaudio).  The difficulty there would be the
> > > necessity
> > > of encoding everything into byte streams.  Perhaps just sprintf/sscanf
> will
> > > do it for you.
> > >
> > > cheers
> > > Miller
> > >
> > > On Tue, Aug 23, 2016 at 03:49:20PM +0200, Marco Matteo Markidis wrote:
> > > > Dear all,
> > > >
> > > > I'm developing an external that has two threads, one audio thread
> and one
> > > > worker thread. The audio thread contains all usual stuff; while the
> > > worker
> > > > thread computes calculations (I need knn searches and so on for my
> > > > resynthesis) and put them in a data structure. At the end of
> > > calculations,
> > > > the worker thread atomically CAS the data structure.
> > > > Actually, I'm using a [readsf~]-like mechanics with pthread signal to
> > > > communicate between threads.
> > > >
> > > > I would like to remove lock and use a lock free system. I don't know
> if
> > > it
> > > > feasible. Moreover I don't know if it has some sense, because Pd
> locks a
> > > > mutex in scheduler and I don't know if a lock free implementation
> could
> > > be
> > > > a right solution.
> > > >
> > > > In the case it could be a solution, I will start with a SPSC circular
> > > queue
> > > > and I will use atomic CAS to swap the data structure.
> > > >
> > > > Best regards,
> > > >
> > > > Marco
> > >
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