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

Waiman Long
2014-06-02T17:33:57Z

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