From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756268Ab0KCSAk (ORCPT ); Wed, 3 Nov 2010 14:00:40 -0400 Received: from claw.goop.org ([74.207.240.146]:47531 "EHLO claw.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753115Ab0KCSAi (ORCPT ); Wed, 3 Nov 2010 14:00:38 -0400 Message-ID: <4CD1A33E.6040105@goop.org> Date: Wed, 03 Nov 2010 14:00:30 -0400 From: Jeremy Fitzhardinge User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.12) Gecko/20101027 Fedora/3.1.6-1.fc13 Lightning/1.0b3pre Thunderbird/3.1.6 MIME-Version: 1.0 To: Eric Dumazet CC: Peter Zijlstra , Linux Kernel Mailing List , Jan Beulich , Avi Kivity , Xen-devel , "H. Peter Anvin" , Linux Virtualization , Srivatsa Vaddagiri , Jeremy Fitzhardinge Subject: Re: [PATCH 03/20] x86/ticketlock: Use C for __ticket_spin_unlock References: <20092775a9df07a5a75820ac250194b535279d51.1288794124.git.jeremy.fitzhardinge@citrix.com> <1288797218.2511.143.camel@edumazet-laptop> In-Reply-To: <1288797218.2511.143.camel@edumazet-laptop> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/03/2010 11:13 AM, Eric Dumazet wrote: > Le mercredi 03 novembre 2010 à 10:59 -0400, Jeremy Fitzhardinge a > écrit : >> From: Jeremy Fitzhardinge >> >> If we don't need to use a locked inc for unlock, then implement it in C. >> >> Signed-off-by: Jeremy Fitzhardinge >> --- >> arch/x86/include/asm/spinlock.h | 33 ++++++++++++++++++--------------- >> 1 files changed, 18 insertions(+), 15 deletions(-) >> >> diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h >> index 6711d36..082990a 100644 >> --- a/arch/x86/include/asm/spinlock.h >> +++ b/arch/x86/include/asm/spinlock.h >> @@ -33,9 +33,23 @@ >> * On PPro SMP or if we are using OOSTORE, we use a locked operation to unlock >> * (PPro errata 66, 92) >> */ >> -# define UNLOCK_LOCK_PREFIX LOCK_PREFIX >> +static __always_inline void __ticket_unlock_release(struct arch_spinlock *lock) >> +{ >> + if (sizeof(lock->tickets.head) == sizeof(u8)) >> + asm (LOCK_PREFIX "incb %0" >> + : "+m" (lock->tickets.head) : : "memory"); >> + else >> + asm (LOCK_PREFIX "incw %0" >> + : "+m" (lock->tickets.head) : : "memory"); >> + >> +} >> #else >> -# define UNLOCK_LOCK_PREFIX >> +static __always_inline void __ticket_unlock_release(struct arch_spinlock *lock) >> +{ >> + barrier(); > technically speaking, it should be : smp_wmb() Perhaps. In practise it won't make a difference because it is defined as barrier() unless OOSTORE is defined, in which case we need to do a locked increment anyway. Thanks, J