NOUX limitations

[Norman Feske]

Hi Daniel,

> Can someone explain the current limitations of NOUX?  I set up my own NOUX
> package, then tried to call POSIX sleep and got the error "Invalid attempt
> to create a thread besides main".  Why is this?  

Noux is meant as a solution to enable the use of command-line-based GNU
software on Genode. I am referring to classical Unix software such as
compilers, shells, and utilities that interact with each other using
pipes and files.

This is where Noux draws its line. It does not even attempt to provide
functionalities that go beyond the scope of Unix.

> I also see that pthreads are not functional for NOUX.  Is there a specific
> reason for this?  Can you tell me what your roadmap for NOUX is?

POSIX threads would make Noux more complex but bring not much benefit.
None of the tools we want to use with Noux requires them. My personal
stance on the subject is that most use cases for 'pthreads' in the world
of Unix can and should be accommodated with classical Unix mechanisms
(e.g., using select, fork, and pipes). If your application requires
POSIX threads (as is the case for many GUI applications, or a Java
virtual machine, or other runtimes), it is better to run it as a normal
Genode component w/o using Noux. In this case, the 'pthread' library in
the 'libports' repository might be a good starting point.

Do you think that this line of thinking is reasonable?

Regarding your question about the road map, the Noux development is
driven by the programs that we want to use. In the previous months, we
concentrated on enabling the functionality needed to run the Genode tool
chain. There is work in progress to bring Git to Noux as well. We will
continue to address all the programs that we need to use Genode as a
development environment.

Whereby we have originally focused our attention on mere functionality,
we just started to look into optimizations. For example, we recognized
that executing the Genode tool chain on Noux is slower than on Linux.
Consequently we are investigating ways to detect the bottlenecks and
speed it up. Until mid 2013, we plan to add support for starting Genode
subsystems out of a Noux environment. So the worlds of Noux and plain
Genode components will come closer together.

However, multi-threaded Noux applications are not on the list. That
said, I do not want to discourage your from trying to add
pthread-support into Noux yourself. Maybe I am wrong and this addition
is less complex than I think?

Coming back to your question about sleep. In this case, the 'sleep'
function uses the libc's default implementation, which tries to spawn a
timer thread on the first call. On Noux, we detect (and prevent) the
creation of threads other than the main thread. So we would need to
override the default 'sleep' function. This is apparently missing since
'sleep' remained unused by all the Noux programs that we ported so far.
If you like to see it added, would you like to open a new topic in our
issue tracker?

Cheers
Norman

-- 
Dr.-Ing. Norman Feske
Genode Labs

http://www.genode-labs.com · http://genode.org

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Geschäftsführer: Dr.-Ing. Norman Feske, Christian Helmuth