#4400: Asynchronous exceptions in runInUnboundThread
---------------------------------+------------------------------------------
Reporter: basvandijk | Owner:
Type: proposal | Status: new
Priority: normal | Component: libraries/base
Version: 6.12.3 | Keywords:
Testcase: | Blockedby:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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When you throw an asynchronous exception to a thread which is executing:
`runInUnboundThread m`, `m` will keep executing and there's no way to kill
it.
I propose to catch asynchronous exceptions in `runInUnboundThread` and
throw them to the thread which is executing `m`. `m` in turn can decide to
catch or ignore them. In case `m` decides to ignore them or to rethrow
them, the exception will be rethrown in the current thread:
{{{
runInUnboundThread :: IO a -> IO a
runInUnboundThread action = do
bound <- isCurrentThreadBound
if bound
then do
mv <- newEmptyMVar
mask $ \restore -> do
tid <- forkIO $ Exception.try (restore action) >>= putMVar mv
let wait = takeMVar mv `Exception.catch` \(e :: SomeException) ->
Exception.throwTo tid e >> wait
wait >>= unsafeResult
else action
unsafeResult :: Either SomeException a -> IO a
unsafeResult = either Exception.throwIO return
}}}
The attached patch implements this behaviour.
(Note there are two other bug-fix patches in the bundle that this patch
depends on which can be independently applied.)
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4400>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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