linux-kernel - Re: [PATCH 13/14] x86/ticketlock: add slowpath logic

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Message-ID: <4CE39B7A.1080706@goop.org>
Date:	Wed, 17 Nov 2010 01:08:10 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Jan Beulich <JBeulich@...ell.com>
CC:	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Nick Piggin <npiggin@...nel.dk>,
	Peter Zijlstra <peterz@...radead.org>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Xen-devel <xen-devel@...ts.xensource.com>,
	Avi Kivity <avi@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
	xiyou.wangcong@...il.com, Eric Dumazet <dada1@...mosbay.com>,
	Linux Virtualization <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH 13/14] x86/ticketlock: add slowpath logic

On 11/17/2010 12:56 AM, Jeremy Fitzhardinge wrote:
> On 11/17/2010 12:52 AM, Jeremy Fitzhardinge wrote:
>> But, yes, %z0 sounds interesting.  Is it documented anywhere?  I think
>> I've tried to use it in the past and run into gcc bugs.
> This one: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39590
>
> Should be OK in this case because there's no 64-bit values to be seen...
Hm, it fails when __ticket_t is 16 bits:

/home/jeremy/git/linux/arch/x86/include/asm/spinlock.h: Assembler messages:
/home/jeremy/git/linux/arch/x86/include/asm/spinlock.h:73: Error: suffix
or operands invalid for `or'

        lock; ors $1, 2(%rbx)   #,


So I don't think that's going to work out...

    J
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