Bug in IO manager when increasing the number of capabilities

The new IO manager in HEAD has a logic error in the function responsible for creating more IO manager threads after increasing the number of capabilities with setNumCapabilities. This results in an index-out-of-range error later on in the program when one perform blocking IO.

Test case:

import GHC.Conc

main = do
    setNumCapabilities 2
    getLine

$ ghc-stage2 -threaded program.hs
$ ./program
program: Ix{Int}.index: Index (1) out of range ((0,0))

The fix is simple and will be arriving shortly.

Trac metadata

Trac field	Value
Version	7.7
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	libraries/base
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture