Thread specific breakpoints

GDB allows breakpoints to be set that are specific to a single thread

  break <addr> thread <threadno>

This is implemented for a remote target by using a Z0 (or Z1 for a
hardware breakpoint) packet, but this is assumed to set a breakpoint
that will stop any thread. In the event that any other thread hits this
breakpoint, the GDB client will automatically continue it. Only when the
required thread hits the breakpoint is it reported.

For a real-time system, this is potentially disruptive, and with a large
number of threads, inefficient.

I have a RTOS with support for thread specific breakpoints. So I would
like a way to pass the thread ID with the Z0/Z1 packet (and for
completeness the z0/z1 packet). One way I have considered is to use the
KIND argument passed with Z0/Z1 to identify the thread. Another is to
extend the Z packets to allow an optional thread field.

I'd welcome comments on using this approach, or suggestions of a better way.

Thanks,


Jeremy

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