From: Jeff Dike <jdike@addtoit.com>
To: John Reiser <jreiser@BitWagon.com>
Cc: user-mode-linux-devel@lists.sourceforge.net
Subject: Re: [uml-devel] why allocate page for stack in clone(, stack, ~CLONE_VM & (...)) ?
Date: Thu, 1 Nov 2007 22:25:40 -0400 [thread overview]
Message-ID: <20071102022540.GA12253@c2.user-mode-linux.org> (raw)
In-Reply-To: <472A4DAC.3060104@BitWagon.com>
On Thu, Nov 01, 2007 at 03:05:32PM -0700, John Reiser wrote:
> In arch/um/os/start_up.c, function start_ptraced_child() does:
> pid = clone(ptrace_child, (void *) sp, SIGCHLD, NULL);
> where sp points into a newly- mmap()ed page. Instead, why not
> avoid the mmap() entirely via:
> pid = clone(ptrace_child, NULL, SIGCHLD, NULL);
>
> Because the flags to clone() do not contain CLONE_VM, then the clone()
> is equivalent to a fork() with respect to address space.
If you look at what's currently in mainline, you'll see it does
exactly what you suggest - the patch in question is this one:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=3cdaf45578b9aa1eb748d0a32678ee5a0180575b
Jeff
--
Work email - jdike at linux dot intel dot com
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prev parent reply other threads:[~2007-11-02 2:25 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-01 22:05 [uml-devel] why allocate page for stack in clone(, stack, ~CLONE_VM & (...)) ? John Reiser
2007-11-02 2:25 ` Jeff Dike [this message]
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