[GHC] #9722: ghcirun004 intermittently fails with ghc: ioManagerWakeup: write: Bad file descriptor

[GHC]

#9722: ghcirun004 intermittently fails with ghc: ioManagerWakeup: write: Bad file
descriptor
-------------------------------------+-------------------------------------
        Reporter:  ezyang            |                   Owner:  simonmar
            Type:  bug               |                  Status:  new
        Priority:  high              |               Milestone:  7.10.1
       Component:  Runtime System    |                 Version:  7.9
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Runtime crash     |  Unknown/Multiple
      Blocked By:                    |               Test Case:  ghcirun004
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
-------------------------------------+-------------------------------------
Changes (by thomie):

 * cc: simonmar (added)
 * owner:   => simonmar
 * component:  GHCi => Runtime System


Comment:

 I can reproduce the notorious 'ioManagerWakeup' bug. Not for `ghci004`
 itself, but for some other ghci tests.

 On my puny laptop with only 2 cores, I do the following:

 1. Make sure the cpu is plenty busy, by running `ghc -e [0..] > /dev/null`
 in 3 different shells.

 2. Run `make test EXTRA_HC_OPTS='+RTS -I0.1 -RTS' TEST='print002 print003
 print006 print007 print008 print010'`


 For me, all tests always fail with:

   "ioManagerWakup: write: Bad file descriptor"

 Step 2 sets the 'GC idle time' for ghci script tests to 0.1 seconds (from
 the default for GHC/GHCi of 5 seconds, see #3408); the same value that is
 used for other tests with WAY=ghci (among which `ghci004`).

 The necessity of step 1 might explain why we don't see the bug when
 running a single test in isolation, but only when running validate, which
 runs a lot of tests at the same time.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9722#comment:14>
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