Core awareness
==============

This document specifies MI extensions to inform the client about cores on
which threads are executed. 

While the mapping from thread to core is volatile for traditional Linux
applications, it can be fixed for Linux application that specifically
pin threads, and is often fixed for embedded systems, and for those cases,
making frontend aware of the mapping would be nice.

The proposed changes affect the 'thread groups' interface, and are as
follows:

1. The output of the --list-thread-groups command will include a new
field, 'cores'. For the 'process' thread group it will a list of all
cores on which threads in that group are currently running. For leafs,
that field should be a list with a single element. The new field will
be output regardless of whether the --available option is specified.

Example:

   -list-thread-groups --available
   ^done,groups=[{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]}]

2. To cut down on the number of roundtrips, the --list-thread-groups without
parameters may optionally recurse into the thread hierarchy. New option, 
'--recurse N' will be used to control that. Originally, N will be required 
to be 1. The --recurse option can be used independelty from the --available
option.

Example:

   -list-thread-groups --available --recurse 1
    ^done,groups=[{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
                   threads=[{id="1",target-id="Thread 0xb7e14b90",cores=[1]},
                            {id="2",target-id="Thread 0xb7e14b90",cores=[2]}]}]

Note that when --available is specified together with --recurse, some targets
may not be able to honor the request. In that case, the 'threads' field will be
absent from the output. The frontend should be prepared to handle this situation.

[CONSIDER: Shall -list-target-features report if --available + recurse works?]

3. It will be possible to pass several group ids to --list-thread-groups. In
that case, the output will be identical to that of '-list-thread-groups'
without parameters, except that thread groups that were not listed as
parameters will not be output. This will be allowed both with and without
--available and --recurse.

Example:

   -list-thread-groups --available --recurse 1 17 18
    ^done,groups=[{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
                   threads=[{id="1",target-id="Thread 0xb7e14b90",cores=[1]},
                            {id="2",target-id="Thread 0xb7e14b90",cores=[2]}]}]


[NOTE: explicitly mention in the manual that output when either no thread
group is specified, or >1 thread group is specified has 'groups' as top-level
element, while output when one group is specified has just 'threads' element
at the top level]

4. The *stopped notification will include a new field 'core', giving the core
number on which the breakpoint is hit. This field will only be present if
possible.