Shutting Down the RTS
Mon, 13 Jan 2003 00:41:17 +0100
I'm almost ready to send in a patch that should fix most of the current
issues with the threaded RTS.
But.... I'm stuck at the problem of terminating the RTS in a proper way.
According to the GHC manual, a concurrent Haskell program should
terminate when the main action terminates. This sounds reasonable and
matches the behaviour of C programs on most platforms.
In the threaded RTS, this behaviour has never been implemented. We
can't simply return from schedule(), because we might no longer be
running in the thread of the RTS main() routine. The thread where
rts_mainEvalIO was called might be busy executing some foreign code
that we know nothing about.
(Im)possible solution #1: As soon as the main action terminates, call
shutdownHaskellAndExit(). At first, this seems to work fine.
But then, shutdownHaskellAndExit() comes along and tries to run
finalizers. For every finalizer, the RTS is started back up again using
rts_mainEvalIO(), and this time, we really have to exit by returning
Possible solution #2: Forget about running finalizers at program
termination and just exit().
In most of the situations where I'd use finalizers, I don't need to run
them upon program termination, the OS cleans up after me. Also, the
finalizers are not run in the correct order anyway, and there are
situations where running them in the wrong order might be worse than
not running them at all.
And, most of all, solution #2 is easy to implement.
Can somebody suggest a third solution, or shall I go for #2 for the