[GHC] #9003: GHC eventlog: thread stop status codes modified (breaking ghc-events, threadscope, edentv)

[GHC]

#9003: GHC eventlog: thread stop status codes modified (breaking ghc-events,
threadscope, edentv)
-------------------------------+-------------------------------------------
        Reporter:  jberthold   |            Owner:  simonmar
            Type:  bug         |           Status:  new
        Priority:  normal      |        Milestone:  7.8.3
       Component:  Runtime     |          Version:  7.8.2
  System                       |         Keywords:
      Resolution:              |     Architecture:  Unknown/Multiple
Operating System:              |       Difficulty:  Easy (less than 1 hour)
  Unknown/Multiple             |       Blocked By:
 Type of failure:  Other       |  Related Tickets:
       Test Case:              |
        Blocking:              |
-------------------------------+-------------------------------------------
Changes (by jberthold):

 * cc: jberthold (added)


Comment:

 Like the GHC-6.x tid field length problem, any solution to the problem
 requires baking in knowledge of GHC version differences into ghc-events
 (might break other software that writes event log format).

 A fix in ghc-events is possible (the fork ghc-events-parallel has been
 fixed like this as a temporary solution): EVENT_USER_MARKER was added
 after the 7.6 branch, so the ghc-events parser can use it as an indication
 to use different thread stop state decoders. When fixing it like this,
 however, older tools will always yield the error.

 OTOH, when reverting to the original encoding in GHC (fix inside GHC), one
 needs to reliably detect GHC-7.8.2 and distinguish it from subsequent
 versions. Again by adding a new event type in master and GHC-7.8.3.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9003#comment:1>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler