[GHC] #11075: Confusing parallel spark behaviour with safe FFI calls

[GHC]

#11075: Confusing parallel spark behaviour with safe FFI calls
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        Reporter:  duncan            |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Runtime System    |              Version:  7.10.2
      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 duncan):

 So thoughtpolice has a very sensible suggestion: annotate this info in the
 FFI call. That is, rather than just safe and unsafe, we can add an extra
 bit to say it's safe but cpu intensive. Then the scheduler could keep note
 of this when it makes the new thread for the FFI call. When there are
 outstanding cpu intensive C calls that this cap is waiting on, then don't
 consider the cap idle for the purposes of grabbing and converting new
 sparks.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11075#comment:1>
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