Re: pfCycleBuffers

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Remi Arnaud (remi++at++remi.asd.sgi.com)
Thu, 10 Oct 1996 16:24:38 -0700

On Oct 10, 6:13pm, Scott McMillan wrote:
> Subject: pfCycleBuffers
>
> Somebody please tell me where I am going wrong....
>
> My pass-through data (for frame accurate data passing from APP to DRAW) is
> getting rather large and from what I understand it actually copies data from
> one process to the next. I would like to replace this with pfCycleBuffers,
> but so far I have had no success. I have read the examples in the man pages
> and I assume I want to follow the libpf example (like in morph.C). Here's
> what I am doing:
>
> Global variable:
>
> pfCycleBuffer *G_cbuf;
>
>
> In APP, after pfConfig, pfMultiprocess, and pfInit and before the main loop:

 It maybe a typo, but here you declare G_cbuf,

> G_cbuf = new(pfGetSharedArena()) pfCycleBuffer(sizeof(myDataStruct));

 And here, you use G_cycle_buffer ?

> myDataStruct *curr_data = (myDataStruct *)
G_cycle_buffer->getCurData();
>
> // initialize curr_data here
>
> G_cbuf->init(G_cycle_buffer->getData());
>
>
> In APP, during main sim loop, just before pfFrame:
>
> curr_data = (myDataStruct *) G_cycle_buffer->getCurData();
> // update data here
> G_cycle_buffer->changed();
>
>
> In DRAW callback:
>
> myDataStruct *draw_data (myDataStruct *) G_cycle_buffer->getCurData();
> // do something with the data here

 You cannot acces to G_cbuf from here, as the Draw process is forked BEFORE the
Cycle buffer is declared. So the G_cbuf is not initialized for DRAW.

>
> When I run this, I get the following message and a core dump (bus error):
>
> PF Notice: Caught SIGCHLD. Exiting due to death of child with pid 4103.
>
> And dbx reports the following:
>
> PC value from core file (0x40d7f0) is not part of the program.
> Assuming return register value (0x40d7f0) usable to locate PC.
> Core from signal SIGBUS: Bus error
> (dbx) where
> > 0 drawChannel(pfChannel*,void*)(0x1807b0d0, 0x0, 0x0, 0x3f800000)
["pfchannels.C":229, 0x40d7f0]
> 1 pfChannel::pf_callDrawFunc(void)(0x181a62e0, 0x0, 0x0, 0x3f800000)
["../../../lib/libpf/pfChannel.C":1996, 0x5b33e04c]
> 2 doDraw(pfChannel*,pfPipe*,int*)(0x181a62e0, 0x1807fdf0, 0x7fff28d4,
0x3f800000) ["../../../lib/libpf/pfProcess.C":4493, 0x5b379018]
> 3 mpDraw(void)(0x0, 0x0, 0x0, 0x3f800000)
["../../../lib/libpf/pfProcess.C":4924, 0x5b37a16c]
> 4 pfConfig(0x0, 0x1807ad00, 0x0, 0x3f800000)
["../../../lib/libpf/pfProcess.C":1765, 0x5b37264c]
> 5 ::initializePerformer(void)(0x0, 0x0, 0x0, 0x3f800000)
["pfchannels.C":99, 0x40cecc]
> 6 main(0x7fff2e98, 0x7fff2f04, 0x0, 0x3f800000) ["main.C":87, 0x409ae0]
> 7 __istart() ["crt1tinit.s":13, 0x409740]
>
>
> Line 229 in drawChannel() is the first line in the DRAW callback snippet
above.

 Yes, And I bet G_cycle_buffer is NULL

> Also note: I have a 2 processor IR, I am using PFMP_APPCULL_DRAW,
> and G_cbuf->getConfig() returns 4. (????)

 This is ok.

>
>
> As always, any help is greatly appreciated,
> scott

 To solve this problem, allocate a pointer to a pfCyclebuffer in shared memory,
before pfConfig. All processes will have a pointeur to a (pfCycleBuffer*) in
shared memory.

 -- Remi

-- 




 o o  Remi ARNAUD - Silicon Graphics, Performer, Advanced Systems Dev      o o 
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