Re: [PATCH v2] introduce atomic_pointer to fix a race condition in cancelable mcs spinlocks

[Waiman Long]

On 06/02/2014 12:30 PM, Peter Zijlstra wrote:
> On Mon, Jun 02, 2014 at 06:25:25PM +0200, Peter Zijlstra wrote:
> > I'm almost inclined to just exclude parisc from using opt spinning.
> >
> > That said, this patch still doesn't address the far more interesting
> > problem of actually finding these issues for these few weird archs.
> So why do these archs provide xchg() and cmpxchg() at all? Wouldn't it
> be much simpler if archs that cannot sanely do this, not provide these
> primitives at all?

I believe xchg() and cmpxchg() are used in quite a number of places 
within the generic kernel code. So kernel compilation will fail if those 
APIs aren't provided by an architecture.

-Longman
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