Re: Memory allocator semantics

Paul E. McKenney
2014-02-11T12:09:24Z

On Tue, Feb 11, 2014 at 10:50:24AM +0200, Pekka Enberg wrote:
> Hi Paul,
>
> On Sun, Feb 9, 2014 at 4:00 AM, Paul E. McKenney
> <paulmck@linux.vnet.ibm.com> wrote:
> > From what I can see, (A) works by accident, but is kind of useless because
> > you allocate and free the memory without touching it. (B) and (C) are the
> > lightest touches I could imagine, and as you say, both are bad. So I
> > believe that it is reasonable to prohibit (A).
> >
> > Or is there some use for (A) that I am missing?
>
> So again, there's nothing in (A) that the memory allocator is
> concerned about. kmalloc() makes no guarantees whatsoever about the
> visibility of "r1" across CPUs. If you're saying that there's an
> implicit barrier between kmalloc() and kfree(), that's an unintended
> side-effect, not a design decision AFAICT.

Thank you. That was what I suspected, and I believe that it is a
completely reasonable response to (A).

Thanx, Paul