with -threaded, infinite loops run too slowly

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.

Trac metadata

Trac field	Value
Version	6.4.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Runtime System
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