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Date: Mon, 23 Jan 2006 20:01:51 -0700 (MST)
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To: deischen@freebsd.org
From: "M. Warner Losh" <imp@bsdimp.com>
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References: <43D56E79.60504@elischer.org>
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	Mon, 23 Jan 2006 20:01:29 -0700 (MST)
Cc: freebsd-current@freebsd.org, rwatson@freebsd.org, julian@elischer.org
Subject: Re: kernel thread as real threads..
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In message: <Pine.GSO.4.43.0601231954150.17167-100000@sea.ntplx.net>
            Daniel Eischen <deischen@freebsd.org> writes:
: On Mon, 23 Jan 2006, Julian Elischer wrote:
: 
: > Robert Watson wrote:
: >
: >
: > well, the operation woudll continue for the parent only I woudl assume.
: >
: > > (although davidxu is changing that)
: >
: > I'm not convinced that that multiple threads should be allowed to
: > proceed during a fork
: > but I can see that not allowing it is more a "foot shooting avoidance"
: > than a requirement.
: > it could be allowed that if you do a fork and allow multipel threads to
: > runat the same time
: > and end up with an inconsistant address space in the child, then you get
: > what you deserve.
: > :-)
: 
: POSIX specifies that only 1 thread (the forking thread) is present
: after a fork.  If you want all (or some subset) of the parent's
: threads to exist after a fork(), you must call it something
: else (use a flag to rfork?) and ensure it is not the default
: behavior.

The problem that we have today is that single_thread suspends most,
but not all, of the threads.  There are many scenarios where one could
get deadlock if you are sleeping uninterruptably in one thread, but
interruptably in another.

Warner