Re: [9fans] Re: Threads: Sewing badges of honor onto a Kernel

[Lucio De Re <lucio@proxima.alt.za>]

On Thu, Feb 26, 2004 at 11:57:52PM -0800, Linus Torvalds wrote:
>
> On Fri, 27 Feb 2004, Lucio De Re wrote:
> >
> > Is Torvalds really saying that environment[] is held _in_ the stack?!
> > No wonder he was reluctant to copy it!  Specially when using "bash".
> > But I must be mistaken.
>
> Take a look if you don't believe me.
>
> There is a _lot_ of state on the stack. That's how C works.
>
Hm.  Yes, C allows it.  And your point is valid that an arbitrary
data segment may justifiably be copied.  But the stack is traditionally
the repository of special, let's call it "holy" information and
having a thread stomping all over it when another thread gets to
find out the hard way is not a thrilling prospect.

After all, there is nothing to prevent a coder from altering the
return address (traditionally a stack entry) in one thread and
totally wrecking the behaviour of another on return, right?

I still think the acid test lies with whether one version can model
the other.

++L

PS: and I really hope that the arguments and environment variables
are stored elsewhere and only the pointers appear on the stack :-)
I mean, even MS-DOS got that bit "sane", to use a very loaded word
previously used by Linus in this discussion.