When debugging operation systems on PPC440 with simultaneous application/kernel debugging breakpoints af application debugger always result in kernel debugger halt.

That behavior occurs due to the nature of implementing software breakpoints on the PPC440.

The kernel debugger uses the TRAP instruction to patch software breakpoints. The application debugger does it in the same way. It is a typical resource problem. To avoid that problem it is possible to prevent the kernel debugger from setting/using TRAP breakpoint patching via the Jtag Target Interface setup. Enable the Do not use TRAP for software breakpoints option in the PowerPC 440 page via UDE® menu Config -> Target Interface. Be aware that is only possible to use hardware breakpoints with that option enabled.