Date: Fri, 6 Nov 2009 12:02:10 -0600
From: "Serge E. Hallyn" <serue@us.ibm.com>
To: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: linux-kernel@vger.kernel.org, arnd@arndb.de,
       Containers <containers@lists.linux-foundation.org>,
       "Eric W. Biederman" <ebiederm@xmission.com>, hpa@zytor.com,
       Alexey Dobriyan <adobriyan@gmail.com>, roland@redhat.com,
       Pavel Emelyanov <xemul@openvz.org>
Subject: Re: [v11][PATCH 8/9] Define clone_with_pids() syscall
Message-ID: <20091106180210.GA31652@us.ibm.com>
References: <20091105053053.GA11289@us.ibm.com> <20091105054124.GH16142@us.ibm.com>
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Quoting Sukadev Bhattiprolu (sukadev@us.ibm.com):
> +	stack_size = (unsigned long)kca.child_stack_size;
> +	child_stack = (unsigned long)kca.child_stack_base + stack_size;
> +
> +	if (!child_stack)
> +		child_stack = regs->sp;

I'm hooking up the s390 version right now.  Do you think you should
make this

	if (!kca.child_stack_base)
		child_stack = regs->sp;

?

I suppose that in general if I pass in a NULL kca.child_stack_base
I'll also pass in a 0 stacksize, but as a user I'd expect that if
I pass in NULL, the size gets ignored.  Instead, if I pass in NULL
plus a size, then the kernel will take (void *)size as the stacktop.

-serge
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