#7325: threadDelay mistreats minBound and maxBound in some configurations
-----------------------------------------+----------------------------------
Reporter: joeyadams | Owner:
Type: bug | Status: new
Priority: normal | Component: Runtime System
Version: 7.6.1 | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Incorrect result at runtime | Testcase:
Blockedby: | Blocking:
Related: |
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threadDelay currently treats minBound and maxBound incorrectly in some
cases. This breaks the following idiom
([http://hackage.haskell.org/packages/archive/async/latest/doc/html/src
/Control-Concurrent-Async.html#Concurrently as seen in the async
package]):
{{{
forever (threadDelay maxBound)
}}}
On Linux (Ubuntu 10.04 64-bit) without -threaded, {{{threadDelay
maxBound}}} returns immediately. For lower numbers on the same order of
magnitude, it behaves non-deterministically. For example, given this
program:
{{{
import Control.Concurrent
import Control.Monad
main = forM_ [6244222868950683224..] $ \i -> do
print i
threadDelay i
}}}
threadDelay returns immediately in some cases but not in others. If I
compile and run it in bash like this:
{{{
ghc-7.6.1 -fforce-recomp threadDelay-maxBound.hs ; ./threadDelay-maxBound
}}}
The bug usually appears, but if I run it like this:
{{{
ghc-7.6.1 -fforce-recomp threadDelay-maxBound.hs
./threadDelay-maxBound
}}}
The bug does not appear (threadDelay blocks like it should). Thus, the
program is affected by a very subtle difference in how it is invoked.
Perhaps it is sensitive to file descriptor numbers.
On Windows without -threaded, {{{threadDelay maxBound}}} seems to work,
but {{{threadDelay minBound}}} blocks rather than returning immediately.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7325>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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