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

[Kumar Gala]

On Feb 7, 2014, at 3:02 AM, Torsten Duwe <duwe@xxxxxx> wrote:

> On Thu, Feb 06, 2014 at 02:19:52PM -0600, Scott Wood wrote:
>> On Thu, 2014-02-06 at 18:37 +0100, Torsten Duwe wrote:
>>> On Thu, Feb 06, 2014 at 05:38:37PM +0100, Peter Zijlstra wrote:
>> 
>>>> 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.

>> 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.

- k--
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