[GHC] #825: with -threaded, infinite loops run too slowly

[GHC]

#825: with -threaded, infinite loops run too slowly
-------------------------------+--------------------------------------------
    Reporter:  guest           |        Owner:         
        Type:  bug             |       Status:  new    
    Priority:  normal          |    Milestone:         
   Component:  Runtime System  |      Version:  6.4.2  
    Severity:  normal          |     Keywords:         
          Os:  Linux           |   Difficulty:  Unknown
Architecture:  x86             |  
-------------------------------+--------------------------------------------
This program

 {{{
 a :: ()
 a = a

 main = print a
 }}}

 normally dies with a <<loop>> exception.  However, when compiled with
 -threaded, it just sits, consuming no CPU.  While I know this isn't wrong
 behavior, it severely confounded my expectation that an undefined value
 would either throw an exception or start consuming resources
 conspicuously.  This caused me to go down the wrong alley debugging.

 When watched with strace, I see the program repeatedly doing

 {{{
 12051 --- SIGALRM (Alarm clock) @ 0 (0) ---
 12051 sigreturn()                       = ? (mask now [])
 12051 futex(0x81c0178, FUTEX_WAIT, 1, NULL) = -1 EINTR (Interrupted system
 call)
 }}}

 Another unhappy behavior of this program (compiled with -threaded) is that
 it takes two SIGINTs to kill.

 I'm using the ghc 6.4.2-2 package in Debian, and I saw the same behavior
 with 6.4.1.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/825>
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