[GHC] #8006: Asynchronous exception rethrown synchronously inside runStmt

[GHC]

#8006: Asynchronous exception rethrown synchronously inside runStmt
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    Reporter:  edsko             |       Owner:                  
        Type:  bug               |      Status:  new             
    Priority:  normal            |   Milestone:                  
   Component:  Compiler          |     Version:  7.6.3           
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
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Changes (by simonmar):

  * difficulty:  => Unknown


Comment:

 Thanks for looking into this.  I expect you're right that it's infeasible
 to figure out what to do when `throwTo` returns.

 I would be OK with a solution that did all the lazy loading of interface
 files first before running the snippet, as long as we can be reasonably
 sure that it works. (that is, not just "I tried it and it seems to work",
 but asking somebody who has a reasonable idea of where we do all the
 `unsafePerformIO`s, i.e., simonpj).  I'm not sure, but I think that we
 might lazily read in `IdInfo` from the interface file, so poking on the
 arity of an `Id` might cause an `unsafePerformIO` to happen, and that
 would be outside of the typechecker.

 A couple of other approaches spring to mind:

  * make `forkM` be `forkIO` (or `async`).  I don't know how much overhead
 that would entail, though. We could try it.

  * put a `mask_` inside `forkM`.  Perhaps `uninterruptibleMask` is
 justified in this case, since it's hard to guarantee that we don't have
 any interruptible operations, yet we're reasonably sure that it shouldn't
 block.  However, that might mean we couldn't ^C the typechecker if it
 looped...

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/8006#comment:2>
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