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Date: Mon, 05 May 2003 20:31:33 -0700
From: Terry Lambert <tlambert2@mindspring.com>
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To: Igor Sysoev <is@rambler-co.ru>
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Subject: Re: rfork(RFPROC|RFMEM)
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Igor Sysoev wrote:
> On Mon, 5 May 2003, Terry Lambert wrote:
> What is stack glue ?

See the code in fork1() in /sys/kern/kern_fork.c.


> I use rfork_thread(3) wrapper that allows to setup another stack for
> rfork()ed process.
>
> What RFTHREAD flag does ?

See the code.  It basically sets up for kernel threading, rather
than merely for processes sharing the same address space and/or
file descriptor table and/or heap, which is what rfork was
intended to be able to do.  It also ensures propagation of any
SIGKILL to all peers, so they die all at once, in exit1() in 
/sys/kern/kern_exit.c.


> By the way linuxthreads port always uses RFTHREAD flag.

They don't know any other way than the moral equivalent of
the Linux "clone" system call, so that's what they use; it's
technically not necessary.  See also the source code in the
directory /usr/src/lib/libpthread, which doesn't use rfork()
at all.

-- Terry