linux-kernel - Re: Serious problem with ticket spinlocks on ia64

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Date:	Fri, 27 Aug 2010 22:41:14 +0200
From:	Petr Tesarik <ptesarik@...e.cz>
To:	"Luck, Tony" <tony.luck@...el.com>
Cc:	"linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Hedi Berriche <hedi@....com>
Subject: Re: Serious problem with ticket spinlocks on ia64

On Friday 27 of August 2010 22:29:41 Luck, Tony wrote:
> > If this is a memory ordering problem (and that seems quite plausible)
> > then a liberal sprinkling of "ia64_mf()" calls throughout the spinlock
> > routines would probably make it go away.
>
> I think I take this back ... if it were a memory ordering problem, then
> it could show up any time - not just at wrap-around.

Well, I wasn't originally sure if it only happens at wrap-around. OTOH I've 
now modified my tests, so that they would also catch any other badness, and I 
still only got another two failures after wrap-around.

>From looking at the traces, I'm afraid this smells like another Itanium 
erratum. I'm now trying to write a minimal test case...

Petr Tesarik
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