[Vm-dev] opening a unix pipe via external FFI call

[Douglas McPherson]

The problem was the linux interval timer interfering with system calls. After re-building the VM with the threaded heartbeat everything works, (or works so far)!  

I managed to get all 16 RISC cores to participate in a very simple parallel task, each filling in their portion of a 256 element buffer. Useless, but cool :)

On Sep 11, 2014, at 18:06 , Douglas McPherson wrote:

> Hi,
> 
> Short: 
> Does anyone know offhand of pitfalls trying to make system calls through pipes via FFI from Squeak on Linux (Ubuntu 14.04 on ARM if it makes a difference)?
> 
> Long:
> I’ve been having fun playing with the Parallella board [1]. The Parallella board has a Xilinx dual-core ARMv7 with a small FPGA, and an Epiphany coprocessor which has 16 RISC cores.
> 
> I managed to get a CogStackVM running on (one of the) ARM cores. Based on Tim’s CogStackVM for the RPi (ARMv6), I made some hacks to get it working on the BeagleBoneBlack (ARMv7). This ARMv7 version was compiled on a Chromebook by Ken Dickey where it magically worked, and now by me on the Parallella where it also “just works”. 
> 
> So I wanted to see if I could fire up any of the Epiphany cores. I loaded Squeak OpenCL FFI bindings [2] (very cool) and have been able to do some very simple things such as query the Epiphany capabilities, and create Epiphany buffers and write/read them. So far so good.
> 
> If you want to induce any of the Epiphany’s cores to do some actual work, you have to provide some code (kernel in OpenCL-speak). These can be compiled and loaded on the fly by an OpenCL library API. This is where I am stuck.
> 
> The OpenCL library for the Parallella is open source so I can see exactly where things go wrong. When the kernel compile API is called, it performs its work by making a bunch of system calls via popen(<cmd>, “r”). None of these works; both Squeak and the command are deadlocked once the first popen() call is made. I rebuilt the OpenCL library from sources with debug enabled, as well as added some additional debug prints. 
> 
> In order to communicate with the Epiphany, processes need to be run as root, thus I am running Squeak as root for these tests. And since Squeak is running as root I don’t suspect permission problems getting access to commands and files.
> 
> The OpenCL library for Parallella compiles kernels successfully for test programs written in C, so /it/ should be ok. And the Squeak OpenCL bindings seem to work fine (insofar as I have played with them; that alone is a lot of fun :)) on a Mac with GPU.
> 
> I know the question is vague, and I’m sure I haven’t provided nearly enough info, but thought I would throw it out there :) 
> 
> Thanks!
> Doug
> 
> [1] http://www.parallella.org
> [2] https://sites.google.com/site/schwaj/home/opencl-binding-for-squeak

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