[PD-dev] clock_delay question

[Ivica Ico Bukvic]

> > Another question related to this. In the netclient.c (maxlib) there is
> > the following code excerpt:
> > 
> > 	/* get's called when connection has been made */
> > static void netclient_tick(t_netclient *x)
> > {
> >     outlet_float(x->x_outconnect, 1);
> > 		/* add pollfunction for checking for input */
> > 	sys_addpollfn(x->x_fd, (t_fdpollfn)netclient_rcv, x);
> > }
> > 
> > Isn't the outlet_float call here unsafe as it is being triggered by an
> > external potentially out-of-sync force (namely connection)? Shouldn't
> > this be done through clock_delay() just to be safe? If I understand this
> > correctly, Pd does audio in 64-byte chunks and then the data processing
> > in between. Is this correct?
> > 
> > If so, how does Pd deal with such events if they happen during the times
> > the pd's message tree is not being traversed (e.g. during the dsp
> > cycle)?
> 
> That is why they are poll functions. The poll functions are polled right 
> after the dsp update, in sys_microsleep(). A select call is made to see 
> if any of the file descriptors are ready for read/writing. So if the 
> socket connects at any random time, the float will only be sent out the 
> outlet after the dsp. Another poll function is then registered to check 
> for received data on the socket.
> sys_microsleep() is called from m_pollingscheduler(), Pd's main loop, in 
> m_sched.c, after the dacs are written, so (as I understand it), it is 
> safe to make calls from a pollfunction. I think it's only outlet writes 
> made directly from the dsp object's perform routine that are dangerous, 
> they should be scheduled for right after the dac writes using 
> clock_delay(0).
> 
> Martin

Thanks for the explanation. I am not sure however how does this apply to
the aforesaid example, so I would greatly appreciate your insight in
that specific scenario. Namely:

In the netclient example is the outlet_float call ok even though the
netclient_tick function containing it is triggered by an external
out-of-sync force (namely network connection)? If so, what ensures that
this particular call is not going to happen right in the middle of other
GUI stuff already being sent out and/or dsp loop as the network client
has no idea when that is actually happening? Shouldn't this be also
clock_delay()?

In other words, are outlet_<something> calls safe to be made from
non-dsp functions no matter when they happen *or* are they safe to be
made only in objects that are being pushed by incoming data streams
(which is typically most of Pd objects, but not all, e.g. such as metro
for instance)? If latter is the case, I would say clock_delay(0) is
necessary even on the aforesaid call.

Likewise, if the latter is the case, this may potentially turn out to be
the source of gui freezes where calls come in the middle of other calls
and therefore cause "missing close-brace" tcl/tk errors.

Best wishes,

Ico