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The best way to circumvent the lack of Thread.kill ?
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Date: | 2005-11-08 (20:34) |
From: | Jonathan Bryant <jtbryant@v...> |
Subject: | Re: [Caml-list] The best way to circumvent the lack of Thread.kill ? |
Ok. Two questions. First of all, what is going on in the Event module? I can't exactly get it to work an I fear I'm missing some important concept. I can't find any documentation other than the interface. Does anybody know of any further documeeentation or have a good explanation of exactly what's going on. Second, the Thread module allows for individual thread signal masks, but no way to signal specific, individual threads. It just has a way to signal one of them pseudo-randomly. Since the signal masks only work under Unix, why isn't Thread.kill mapped to pthread_kill() since that would allow much greater flexibility by allowing individual specific threads to be signaled? --Jonathan On Wed, 2005-11-02 at 13:29, David Teller wrote: > Let me rephrase. I don't want to kill just any thread, I want to send an > exception to whoever is actually synchronising on a channel. Perhaps any > exception can be "distantly thrown", or perhaps only one specific kind. > Something like > > let sender c = > ignore Event.sync (Event.send c 1); > (**Event.send passes an information, > while Event.sync may pass control.*) > ignore Event.sync (Event.send c 2); > ignore Event.sync (Event.send c 4); > ignore Event.sync (Event.kill c) > > and receiver f c = > f Event.sync (Event.receive c); > (**Event.receive receive an information, > while Event.sync may pass control.*) > f Event.sync (Event.receive c); > f Event.sync (Event.receive c); > f Event.sync (Event.receive c); > (*Actually, this operation throws > Event.Closed_channel*) > f Event.sync (Event.receive c) > > in > let c = Event.new_channel () > in > ignore (Thread.create sender c); > try > receiver print_int c > with > x -> (*...*) > > In the case of more than two threads waiting for communication on a > single channel, I would say that they all should receive the exception > during their next Event.sync. > > I agree that this is quite close to your idea of sending thunk > functions, but the additional indirection strikes me as odd for > something which to me looks like a primitive. > > Cheers, > David > > Le mercredi 02 novembre 2005 à 19:43 +0100, Alessandro Baretta a écrit : > > David Teller wrote: > > > > > However, in my mind, all these solutions are the channel equivalent of > > > manual error-handling -- something akin to a function returning an ('a > > > option) instead of an 'a because the result None is reserved for errors. > > > I'm still slightly puzzled as to why this distant killing/raising is not > > > a core feature of channels. After all, unless I'm mistaken, channels are > > > a manner of implementing continuations. I tend to believe I should be > > > able to raise an error (a hypothetical Event.raise/Event.kill) instead > > > of returning/passing a value (as in Event.send). > > > > > > Or did I miss something ? > > > > "Channel" is maybe an inappropriate term for this strange object. An > > Event.channel is more like a single-slot mailbox to pass a message to > > someone. Any number of Threads (zero upwards) can be waiting for > > messages on a channel. There is no obligation that there be exactly one > > thread to kill on the other side. What would happen is try to send a > > hard-kill event on a channel where there is nobody on the other side? > > What if the there is more than one thread? > > > > You are trying to find a way around killing a thread with Thread.kill, > > but there is really no way to cleanly kill a thread asynchronously. A > > clean exit requires some cooperation from the killed thread. > > > > Alex -- --Jonathan Bryant jtbryant@valdosta.edu Student Intern Unix System Operations VSU Information Technology "Das Leben ohne Music ist einfach ein Irrtum, eine Strapaze, ein" Exil." ("Life without music is simply an error, a pain, an exile.") --Frederich Nietzsche "The three cardinal values of a programmer are laziness, impatience, and hubris." --Perl Man Page