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Date: 2005-11-22 (17:32)
From: Alexander S. Usov <A.S.Usov@k...>
Subject: Re: [Caml-list] Threads & Fork
On Tuesday 22 November 2005 16:50, Oliver Bandel wrote:
> On Tue, Nov 22, 2005 at 04:39:07PM +0100, Florian Weimer wrote:
> > * Jonathan Bryant:
> > > I'm confused as to why the attached code hangs.  My understanding of
> > > Unix.fork () is that it completely clones the current process, which in
> > > my understanding, clones the processes's threads as well.  Apparently,
> > > though, that is not the case, because I can't join the thread in both
> > > the parent and the child.
> >
> > I can't speak for the OCaml run-time, but POSIX fork only duplicates
> > the current thread, so the new process is essentially single-threaded.
> I doubt that this is true.
> Unix-fork() copies a complete process.
> If the original has threads, the copy also have.
> I don't think that POSIX handles this different to old Unix API.
> Unix-module should do the same as the C-call of fork(2).
> Threads are running inside a process, like any other
> function. So all should be copied completely.
> But using POSIX-threads and Unix-API can yield to many problems,
> for example POSIX threading signals and Unix-signals are clashing
> together and the behaviour can be undefined...

[Option End]A process shall be created with a single thread. If a 
multi-threaded process calls fork(), the new process shall contain a replica 
of the calling thread and its entire address space, possibly including the 
states of mutexes and other resources. Consequently, to avoid errors, the 
child process may only execute async-signal-safe operations until such time 
as one of the exec functions is called. [THR] [Option Start]  Fork handlers 
may be established by means of the pthread_atfork() function in order to 
maintain application invariants across fork() calls. [Option End]

(c) SUS v3

Best regards,