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xen-devel
[Xen-devel] Re: [PATCH 13/14] x86/ticketlock: add slowpath logic
 
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To:  | 
"Jeremy Fitzhardinge" <jeremy@xxxxxxxx> | 
 
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Subject:  | 
[Xen-devel] Re: [PATCH 13/14] x86/ticketlock: add slowpath logic | 
 
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From:  | 
"Jan Beulich" <JBeulich@xxxxxxxxxx> | 
 
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Date:  | 
Wed, 17 Nov 2010 09:34:40 +0000 | 
 
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Cc:  | 
Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>,	Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>,	Nick Piggin <npiggin@xxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>,	Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>,	Srivatsa Vaddagiri <vatsa@xxxxxxxxxxxxxxxxxx>,	Eric Dumazet <dada1@xxxxxxxxxxxxx>,	Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>,	Avi Kivity <avi@xxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>,	xiyou.wangcong@xxxxxxxxx,	Linux Virtualization <virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx> | 
 
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Delivery-date:  | 
Wed, 17 Nov 2010 01:35:17 -0800 | 
 
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<cover.1289940821.git.jeremy.fitzhardinge@xxxxxxxxxx><cover.1289940821.git.jeremy.fitzhardinge@xxxxxxxxxx>	<97ed99ae9160bdb6477284b333bd6708fb7a19cb.1289940821.git.jeremy.fitzhardinge@xxxxxxxxxx>	<4CE3A1060200007800022B04@xxxxxxxxxxxxxxxxxx>	<4CE397C8.9040901@xxxxxxxx>	<4CE398A0.3040105@xxxxxxxx> <4CE39B7A.1080706@xxxxxxxx> | 
 
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>>> On 17.11.10 at 10:08, Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:
> 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...
Indeed, it's only with 4.5 that non-float operands are properly
supported here. Sad.
Jan
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