[GHC] #13970: Segmentation fault inside threadPaused

[GHC]

#13970: Segmentation fault inside threadPaused
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        Reporter:  albertov          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Runtime System    |              Version:  8.2.1-rc3
      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 albertov):

 Replying to [comment:22 bgamari]:
 > I have managed to reproduce it a few times although it does seem to take
 a while. Moreover, it (perhaps not surprisingly) is quite dependent upon
 paralellism. I was unable to reproduce it in a reasonable amount of time
 on my dual-core, four-thread laptop. However, on my 4-core, eight-thread
 server I was able to reproduce it within ten minutes or so. How many cores
 does your test environment have?

 I'm testing on a 6-core, 12-thread machine. It is indeed hard to reproduce
 although it is no much more frequent. I've noticed that giving a large
 `-N` value to the RTS increases the odds. I'm testing with `-N30`. Have
 you tried increasing this value way over your number of cores?

 Another interesting thing is that without this
 [https://github.com/meteogrid/propag/blob/master/app/Main.hs#L69 pause] I
 was unable to reproduce the crash and noticed that a breakpoint I had set
 at `suspendComputation` was never being hit. Adding this pause causes
 `suspendComputation` to be called multiple times and eventually manifests
 the problem (when running outside gdb). Maybe playing with that pause
 helps increasing the odds in your environment?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13970#comment:23>
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