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

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Date:	Fri, 7 Feb 2014 10:02:48 +0100
From:	Torsten Duwe <duwe@....de>
To:	Scott Wood <scottwood@...escale.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, Paul Mackerras <paulus@...ba.org>,
	Anton Blanchard <anton@...ba.org>,
	Tom Musta <tommusta@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linuxppc-dev@...ts.ozlabs.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] Convert powerpc simple spinlocks into ticket locks

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?

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

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

	Torsten

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