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Re: gdb for multiprocessor machines?



   Date: Fri, 05 Mar 1999 08:30:06 -0500
   From: Mohan Pakkurti <pmohan@cadence.com>

   I am wondering if there is currently any work being done in 
   the area of supporting gdb for machines with multiple processors?
   What is involved? can someone comment on this? thanks.

There are a couple ways to accomplish this.  One is to use threads,
have different threads run on different processors.  GDB's thread
support will generally work unchanged on these kinds of machines,
since the OS handles the thread/processor mapping invisibly.

Another way is to have multiple processes.  GDB has nothing for this,
although the idea has been talked about.  GDB would need some hefty
modifications, since much of its internal data about the inferior
process is tied to global variables, and all this would have to
change.

Finally, there is the coprocessor approach, more often seen in
embedded environments, in which multiple CPUs are executing
instructions from different programs in the same physical address
space.  They may or may not have the same architecture; for instance
there are cell phone designs featuring an ARM and a DSP on the same
chip, and using the same RAM.  Supporting debugging in this kind
of environment is a big challenge for GDB, and will require a lot
more work on the underpinnings.  I'm encouraging people to change
GDB in ways that will facilitate this, but I don't know of anybody
actually tackling this multiple-processor problem.

							Stan