Re: PPMC & rtlinux

[Jon Elson <jmelson-at-artsci.wustl.edu>]

Paul Corner wrote:

> Hi Jon
>
> On Mon, 11 Dec 2000, Jon Elson wrote:
> > But, I can see some possible ways TkEMC could cause real trouble.
> > Probably the biggest one (Ray, you know more about this than
> > anyone) is something to do with the process of initializing variables
> > in the RT task.  If anything in TkEMC scrambles the mechanism
> > that hands those variables across the shared memory, they could
> > literally trash any location in physical memory, by causing a wild
> > pointer in the RT task.  Now, this is a real stretch, since the
> > routines that accept these messages are pretty well put together.
> > On another tack, is there anything in the TCL interpreter and
> > its interface to the GUI that might be affected by a break in
> > program continuity?
>
> As I understand it, for later versions of rtlinux, the message handling is
> no longer done through shared memory. On the 2.2.13-rtl2.0 kernel, I don't
> have any shared memory set aside. An advantage at present, as the hard disk is
> being swapped between a couple of machines with differing amounts of memory.

Hmm, maybe that solves the problem.  So, your machine is reliable?
I'm running a 2.0.36 kernel.

> I cannot get the current CVS source to build on any kernel/rtl combinations at
> present. But I would assume that later kernels no longer require the shared
> memory.

Hmm, well, this is a problem.  I don't mind changing EMC versions, because it
is pretty straightforward to go back to one that works.  But, changing kernels
is a bigger undertaking.

Jon