[GHC] #11830: Disabling idle GC leads to freeze

13 Apr 2016

      #11830: Disabling idle GC leads to freeze
-------------------------------------+-------------------------------------
           Reporter:  NeilMitchell   |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Runtime        |           Version:  8.0.1-rc3
  System                             |
           Keywords:                 |  Operating System:  Linux
       Architecture:                 |   Type of failure:  Incorrect result
  Unknown/Multiple                   |  at runtime
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 I'm currently getting a runtime freeze with a spinning CPU with the latest
 GHC 8.0.1 RC (8.0.0.20160411). Testing 2 months ago on whatever was the
 latest release candidate showed no problems. The reproduction steps are a
 bit long winded:

 * All tested on Ubuntu Linux.
 * Checkout Shake, https://github.com/ndmitchell/shake.git (currently at
 75505baa5fc5d1b99a1162edae6ecf7669f00ed9).
 * {{{cabal install}}}
 * Checkout Ninja, https://github.com/ninja-build/ninja.git (currently at
 78f548880e549c701bd77760e4b3f3a4ee147641).
 * Change to the {{{ninja}}} directory.
 * Run {{{./configure.py --bootstrap}}}
 * Run {{{cp ninja nin}}}
 * Run {{{./nin -t clean}}}
 * Run {{{shake}}}

 Observe that Shake fails to complete and starts spinning on 1 CPU.

 If you modify {{{shake.cabal}}} to remove {{{-with-rtsopts=-I0 -qg -qb}}}
 then it works again and completes in < 1 min. Adding back flags with
 {{{+RTS -I0 -RTS}}} shows that {{{-I0}}} alone is the culprit.

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11830
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