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Date: Fri, 11 Nov 2016 18:47:44 +0000
From: Mark Rutland <>
Cc: Kees Cook <>, Will Deacon <>,
	Greg KH <>,
	David Windsor <>,
	Elena Reshetova <>,
	Arnd Bergmann <>, Thomas Gleixner <>,
	Ingo Molnar <>,
	"H. Peter Anvin" <>
Subject: Re: Re: [RFC v4 PATCH 00/13] HARDENED_ATOMIC

On Fri, Nov 11, 2016 at 06:46:30PM +0100, Peter Zijlstra wrote:
> On Fri, Nov 11, 2016 at 09:43:00AM -0800, Kees Cook wrote:
> > > 1) kref: Used for honest-to-goodness reference counters that want
> > > overflow protection.  Uses a new type: atomic_nowrap_t that has
> > > HARDENED_ATOMIC protection.
> > 
> > Based on other feedback, it sounds like we're better off with
> > refcount_t (which kref could be implemented on top of). And refcount_t
> > would have a limited API: inc, dec_and_test (or whatever is determined
> > as sanely minimal).
> > 
> > > 2) statistical counters: Atomic in all cases, but wraps.
> > 
> > Yup. sequence_t seems to make the most sense on naming, I think. If we
> > want to get crazy, the type could be sequence_wrap_t.
> Why? atomic_t is still perfectly fine here, right?

Having a name that clearly highlights the intended use-case makes it
much more obvious what the expected semantics are, and when it is being
abused. If atomic_t were rarely used directly, bad uses are less likely
to get cargo-culted into new code.

That said, a plethora of use-case specific aliases for the same
underlying implementation is also problematic.


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