#7719: System.Timeout.timeout may leak <<timeout>> exceptions -------------------------+-------------------------------------------------- Reporter: int-e | Owner: Type: bug | Status: new Priority: normal | Component: libraries/base Version: 7.7 | Keywords: Os: Linux | Architecture: x86_64 (amd64) Failure: None/Unknown | Blockedby: Blocking: | Related: -------------------------+-------------------------------------------------- The current implementation of {{{timeout}}} can leak {{{Timeout}}} exceptions if an asynchronous exception is delivered at the wrong time. The most worrysome such case is another {{{Timeout}}} exception raised by surrounding call to {{{timeout}}}. The following program reproduces the issue reliably for me: {{{ import System.Timeout import Control.Monad import Control.Concurrent t d = timeout d $ timeout d $ timeout d $ timeout d $ timeout d $ timeout (10^9) $ threadDelay 100 main = forever $ mapM_ t [1..200] -- > ghc -O2 -rtsopts -threaded --make TT.hs -- > ./TT +RTS -N1 -- TT: <<timeout>> }}} Context: A recent thread on {{{ghc-users}}}, starting with http://www.haskell.org/pipermail/glasgow-haskell- users/2013-February/023811.html, got me thinking about corner cases of timeout handling again. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7719 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler