Re: [RFC v2 6/7] powerpc: atomic: Make atomic{,64}_xchg and xchg a full barrier

Hi Peter,

Please forgive me for the format of my reply. I'm travelling,
and replying from my phone.

2015年10月1日 下午7:28，"Peter Zijlstra" [off-list ref]写道：

On Wed, Sep 16, 2015 at 11:49:34PM +0800, Boqun Feng wrote:

quoted

According to memory-barriers.txt, xchg and its atomic{,64}_ versions
need to imply a full barrier, however they are now just RELEASE+ACQUIRE,
which is not a full barrier.

So remove the definition of xchg(), and let __atomic_op_fence() build
the full-barrier versions of these operations.

Do you want to do a patch for -stable fixing the current implementation?

Good idea! I didn't think of this before, and I'd love to do the patch,
but thing is that I'm not able to use my laptop until Oct 10th.
I will send the patch once I'm back.
Does that work for you?

Regards,
Boqun