Proposal: new signal-handling API
marlowsd at gmail.com
Mon Jul 21 05:43:04 EDT 2008
> Synchronising with signal handlers should be done using ordinary thread
> synchronisation. Have one big signal lock if you like, or one per
> signal, or one per handler - it's up to you.
> It's true that you can't synchronise with other people's signal handlers
> this way. But I think that's a feature, or at least not a bug. Even
> using SIG_IGN or sigprocmask() you couldn't stop a handler that had
> already been started anyway.
It just occurred to me that it would be relatively easy to add back support
for blocking signals in a way that makes sense. We could add one MVar per
signal, and have every signal handler do something like
withMVar sigINT_lock $ \_ -> do ...
(implemented under the hood in the API). That would let us provide a way
to temporarily disable handlers for particular signals.
It would have the effect of serialising the handlers for each signal too,
I'm not sure if that's a good thing. We could provide a back door too,
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