Re: [PATCH] Convert powerpc simple spinlocks into ticket locks

On Fri, 2014-02-07 at 09:51 -0600, Kumar Gala wrote:

On Feb 7, 2014, at 3:02 AM, Torsten Duwe [off-list ref] wrote:

quoted

On Thu, Feb 06, 2014 at 02:19:52PM -0600, Scott Wood wrote:

quoted

On Thu, 2014-02-06 at 18:37 +0100, Torsten Duwe wrote:

quoted

On Thu, Feb 06, 2014 at 05:38:37PM +0100, Peter Zijlstra wrote:

quoted

quoted

Can you pair lwarx with sthcx ? I couldn't immediately find the answer
in the PowerISA doc. If so I think you can do better by being able to
atomically load both tickets but only storing the head without affecting
the tail.

Can I simply write the half word, without a reservation, or will the HW caches
mess up the other half? Will it ruin the cache coherency on some (sub)architectures?

The coherency should be fine, I just can’t remember if you’ll lose the reservation by doing this.

Yes you do.

quoted

quoted

Plus, sthcx doesn't exist on all PPC chips.

Which ones are lacking it? Do all have at least a simple 16-bit store?

Everything implements a simple 16-bit store, just not everything implements the store conditional of 16-bit data.

Ben.

- k--
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