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Date: Wed, 17 Nov 2010 08:31:50 +0000
From: "Jan Beulich" <JBeulich@novell.com>
To: "Jeremy Fitzhardinge" <jeremy@goop.org>
Cc: "Jeremy Fitzhardinge" <jeremy.fitzhardinge@citrix.com>,
        "Eric Dumazet" <dada1@cosmosbay.com>, <xiyou.wangcong@gmail.com>,
        "Peter Zijlstra" <peterz@infradead.org>,
        "Nick Piggin" <npiggin@kernel.dk>,
        "Srivatsa Vaddagiri" <vatsa@linux.vnet.ibm.com>,
        "Linux Virtualization" <virtualization@lists.linux-foundation.org>,
        "Xen-devel" <xen-devel@lists.xensource.com>,
        "Mathieu Desnoyers" <mathieu.desnoyers@polymtl.ca>,
        "Avi Kivity" <avi@redhat.com>,
        "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH 13/14] x86/ticketlock: add slowpath logic
References: <cover.1289940821.git.jeremy.fitzhardinge@citrix.com><cover.1289940821.git.jeremy.fitzhardinge@citrix.com>
 <97ed99ae9160bdb6477284b333bd6708fb7a19cb.1289940821.git.jeremy.fitzhardinge@citrix.com>
In-Reply-To: <97ed99ae9160bdb6477284b333bd6708fb7a19cb.1289940821.git.jeremy.fitzhardinge@citrix.com>
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>>> On 16.11.10 at 22:08, Jeremy Fitzhardinge <jeremy@goop.org> 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?

Jan