assorted kernel patches

Albert D. Cahalan acahalan at cs.uml.edu
Thu Aug 23 07:12:29 EST 2001


Paul Mackerras writes:
> Edward Swarthout writes:

>> 1. Support for hardware breakpoints for process threads.
>
> A good idea in general although I will be interested to see
> how this interacts with xmon's and kgdb's use of iabr/dabr.

Who cares? Take a look at the Alpha and i386 Linux ports.
Debugger support for users is important. Kernel hackers can
live without it. (including myself) Go check the linux-kernel
archives to see Linus Torvalds and David S. Miller's opinions
about kernel debuggers.

It would be nice if the ppc port met the Linus standard.

>> 2. Allow superviser (MSR[PR]=0) user threads.
>
> Hmmm, you'll need to explain exactly why this is a good idea
> and why it won't break anything. Without a good strong argument
> I would be inclined to reject this. I don't see what you can do
> with a "user" thread running in supervisor mode that you can't
> do with a kernel module.

It is good for experimenting with processor features.

On an embedded system, it is often nice to turn off interrupts
to do a bit of super-hard real-time from userspace. The user code
may well be incompatible with the kernel. (non-GPL C++ or FORTRAN)

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