[BusyBox] busybox shell ash executing binaries problem

[Rietman, Wijnand - SRQ]

I have got a very weird problem. I am currently evaluating if busybox is suitable for one of our embedded products. This product runs a self-made linux distribution, but for maintenance purposes I would like to switch to busybox. Everything seems to be working fine with busybox, except for one important application. This application is being started from the shell and I am using busybox's build-in shell ash. The application is talking through ttyS2 and ttyS3 to two other devices and is showing a continuously updating status on the console. For some reason it is not able to communicate anymore through ttyS3 when I use busybox's shell ash. TtyS2 is updating just fine.

The application looks like this on the console:

                 1     2     3     4
=====================================
device-1   /     1     1     0     1
device-2       Detector comms failure

If I compile busybox with no shell at all and just use our original ash or bash shell in exactly the same set-up, the application works just fine. When I take a look with "top" or "ps" at all the running processes, I do not notice any differences.

Is there something special on how busybox's shell ash executes binaries or spawns processes? Does anybody have an idea of what could be the cause of this problem? I am running kernel 2.4.22. The application that does not work with the busybox shell ash is commercial software and I do not have the source code of this application...

Thanks,
Wijnand.