Re: vfork & co bugfix

[Linus Torvalds <torvalds@transmeta.com>]

On 11 Jan 1999, Eric W. Biederman wrote:
> 
> >> Question.  Why don't we let CLONE_VFORK be a standard clone flag?
> 
> LT> Because then we're back to the old problem: before doing a vfork(),
> LT> somebody could do a "clone(CLONE_VFORK)" (which would _not_ wait on the
> LT> semaphore like a real vfork() would), and now the wrong child can wake up
> LT> the parent and mess up the real vfork(). 
> 
> Sorry.  I had the implicit assumption that if CLONE_VFORK was a
> standard clone flag, do_fork would include the five lines of semaphore
> code.

Oh, ok.

Sure, makes sense, and is probably the right thing to do - that way you
can (if you really want to) do some strange half-way vfork(), half-way
clone() thing where you share your file descriptors in a vfork(). 

I don't know how useful it would be, but it would be no uglier than doing
it any other way, and I see some advantages (no need for a separate
vfork()  system call - clone() can do it directly). 

I thus remove all my objections,

		Linus

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