Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756416Ab0F3OgM (ORCPT ); Wed, 30 Jun 2010 10:36:12 -0400 Received: from vpn.id2.novell.com ([195.33.99.129]:35760 "EHLO vpn.id2.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752966Ab0F3OgL convert rfc822-to-8bit (ORCPT ); Wed, 30 Jun 2010 10:36:11 -0400 Message-Id: <4C2B72950200007800008DBA@vpn.id2.novell.com> X-Mailer: Novell GroupWise Internet Agent 8.0.1 Date: Wed, 30 Jun 2010 15:36:37 +0100 From: "Jan Beulich" To: "Jeremy Fitzhardinge" Cc: "mingo@elte.hu" , "Stefano Stabellini" , "tglx@linutronix.de" , "Ky Srinivasan" , "linux-kernel@vger.kernel.org" , "hpa@zytor.com" Subject: Re: [PATCH 2/4, v2] x86: enlightenment for ticket spin locks - Xen implementation References: <4C2A200F02000078000089E4@vpn.id2.novell.com> <4C2B1769.5090107@goop.org> <4C2B47190200007800008CB7@vpn.id2.novell.com> <4C2B4564.7030203@goop.org> <4C2B6AD60200007800008D90@vpn.id2.novell.com> <4C2B53D1.90101@goop.org> In-Reply-To: <4C2B53D1.90101@goop.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1059 Lines: 27 >>> On 30.06.10 at 16:25, Jeremy Fitzhardinge wrote: > On 06/30/2010 04:03 PM, Jan Beulich wrote: >> Afaics the unlock still involves a function call *in all cases* with >> pvops spinlocks, whereas it's a single inline instruction without. >> > > No. The unlock path can see if there are any further waiters by looking > at the ticket in the, and only do the kick call if there are some. Are we perhaps talking about different things? I'm referring to static __always_inline void arch_spin_unlock(struct arch_spinlock *lock) { PVOP_VCALL1(pv_lock_ops.spin_unlock, lock); } which is an indirect call which, as I understand it, gets replaced with a direct one at runtime. But it remains to be a call (as opposed to being a single inc instructions without CONFIG_PARAVIRT_SPINLOCKS). Jan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/