Tracepoint enhancements

[Michael Snyder]

Stan Shebs wrote:
> Michael Snyder wrote:
>> [...] a checkpoint
>> represents a machine state.  If there are multiple machines,
>> that complicates the picture -- but basically gdb is saying
>> to the target "I want to be able to return to the state that
>> you are in *right now*".
> Hmm, that is a significant wrinkle to the execution history theory. 
> Basically it's not possible to know reliably whether the execution state 
> of one CPU comes sooner or later than the state of another CPU - their 
> clocks can't be guaranteed to be sync'ed to a sub-instruction level. 
> It's a little like a distributed version control system, where each 
> repository has its own version numbers, and any ordering derives from 
> explicit push/pull instructions. Each inferior can have a reliable 
> execution history, but if you want to go back to state X on CPU 1, you 
> either just affect the one inferior, or expect that other inferiors will 
> go back to the closest available state in their histories.

All true.  I think this sub-branch of the discussion
was mostly blue-sky.