On Fri, Apr 26, 2013 at 9:03 AM, Michael Haberler <mai...@mah.priv.at>wrote:
> Mark, > > > Just being curious, how does the multi-instance RTAI keep from banging > > heads with each other? Lets say we have two instances of RTAI running, > how > > does RTAI keep itself from requiring the same resource as another RTAI > > This multi-instance capability is independent of any specific RTOS and > works with all flavors (RTAI, Xenomai any style, RT-PREEMPT) even across > flavors; you can have a Xenomai kernel, a few Xenomai user RT instances and > a few Posix instances running simultaneously without things going haywire. > Not that that makes any sense, I just mention this works too. > > > instance at the same time, > > "resources" really translates into threads and shared memory > > shared memory is an easy case because all shm is allocated at setup time; > there is no runtime memory allocation in RTAPI land even if it might be > supported as per API description, and it is fact an unnecessary use of a > non-portable OS API, which is why I have removed this and replaced by > standard Posix shm and a single helper driver for kernel threads just fine, > with lots of RTOS-dependent code becoming history in one go. > > all that was needed to coordinate shared memory is clean up the > hodge-podge allocation of shared memory keys here and there, and make an > instance id part of the key > > as for threads, that is quite easy to disambiguate as well > > > > and still maintain the real-time domain of > > having the resource "NOW", when it's needed? > > there is no 'NOW' allocation in allow of LinuxCNC, provided you mean 'NOW' > to mean either task or shm allocation 'within a time critical thread'. It > is all preallocated before the game starts, and _outside_ of any RT > threads, so any fears for collision may be safely put to rest. That case > simply doesnt exist, and I cant conceive one were it suddenly might be > needed. > > - Michael > Michael, I was thinking more of hardware resources, such as interrupts. What happens when both instances require the same interrupt at the same time? Unlike shared memory, interrupts are a bit harder to share, or have concurrent use. Can the separate instances somehow share the IO bus? Or is there some kind of real time scheduler that looks ahead for all possible conflicts, and works it out? Mark ------------------------------------------------------------------------------ Try New Relic Now & We'll Send You this Cool Shirt New Relic is the only SaaS-based application performance monitoring service that delivers powerful full stack analytics. Optimize and monitor your browser, app, & servers with just a few lines of code. Try New Relic and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_apr _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
