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xen-devel
[Xen-devel] Re: [PATCH 13/14] x86/ticketlock: add slowpath logic
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To: |
Jan Beulich <JBeulich@xxxxxxxxxx> |
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Subject: |
[Xen-devel] Re: [PATCH 13/14] x86/ticketlock: add slowpath logic |
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From: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
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Date: |
Wed, 17 Nov 2010 00:52:24 -0800 |
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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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Wed, 17 Nov 2010 00:53:06 -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> |
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On 11/17/2010 12:31 AM, Jan Beulich wrote:
>>>> On 16.11.10 at 22:08, Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:
>> +static inline void __ticket_enter_slowpath(struct arch_spinlock *lock)
>> +{
>> + if (sizeof(lock->tickets.tail) == sizeof(u8))
>> + asm (LOCK_PREFIX "orb %1, %0"
>> + : "+m" (lock->tickets.tail)
>> + : "i" (TICKET_SLOWPATH_FLAG) : "memory");
>> + else
>> + asm (LOCK_PREFIX "orw %1, %0"
>> + : "+m" (lock->tickets.tail)
>> + : "i" (TICKET_SLOWPATH_FLAG) : "memory");
>> +}
> Came only now to mind: Here and elsewhere, did you try using
> %z0 to have gcc produce the opcode suffix character, rather
> than having these somewhat ugly if()-s?
Actually in this case I'm pretty sure there's already a "set bit"
function which will do the job. set_bit(), I guess, though it takes a
bit number rather than a mask...
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.
Thanks,
J
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