[GHC] #15774: SIGKILL only reports backtrace for one capability

[GHC]

#15774: SIGKILL only reports backtrace for one capability
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        Reporter:  bgamari           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Runtime System    |              Version:  8.6.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 There is the question of what the precise semantics of SIGKILL should be.
 Should we dump the state of all threads, all schedulable threads, or only
 currently scheduled threads? My feeling is the latter.

 This isn't entirely trivial to implement, especially given that we need to
 ensure that the output is readable (e.g. prevent interleaving of output
 from different capabilities). One option would be to add a new Message
 variety which can be used to request a backtrace from a capability. The
 thread handling the SIGKILL could then send this message to each
 capability and wait for their replies and print the result. This sounds
 complex for a debugging feature, however.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15774#comment:1>
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