Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754042Ab1BGQ0u (ORCPT ); Mon, 7 Feb 2011 11:26:50 -0500 Received: from mx1.redhat.com ([209.132.183.28]:17014 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752428Ab1BGQ0t (ORCPT ); Mon, 7 Feb 2011 11:26:49 -0500 Message-ID: <4D501D43.5060608@redhat.com> Date: Mon, 07 Feb 2011 18:26:43 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20101209 Fedora/3.1.7-0.35.b3pre.fc14 Lightning/1.0b3pre Thunderbird/3.1.7 MIME-Version: 1.0 To: Jan Kiszka CC: Zachary Amsden , Marcelo Tosatti , kvm , Linux Kernel Mailing List Subject: Re: [PATCH] KVM: x86: Convert tsc_write_lock to raw_spinlock References: <4D4BCB97.6000900@siemens.com> <4D4C698A.4010201@redhat.com> <4D4FD8EE.6040009@siemens.com> <4D4FFD97.6010805@redhat.com> <4D5008F0.5060200@siemens.com> <4D500C9F.2080501@redhat.com> <4D50120F.4030809@siemens.com> <4D501547.6040907@redhat.com> <4D501698.1000507@siemens.com> In-Reply-To: <4D501698.1000507@siemens.com> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1390 Lines: 34 On 02/07/2011 05:58 PM, Jan Kiszka wrote: > On 2011-02-07 16:52, Avi Kivity wrote: > > On 02/07/2011 05:38 PM, Jan Kiszka wrote: > >>> > >>> I don't know as it is allowed to sleep, it doesn't call any sleeping > >>> functions to my knowledge. What worries me in the RT case is that the > >>> spinlock acquired for hardware_enable might be preempted and run on > >>> another CPU, which obviously isn't what you want. > >> > >> I see now, there are calls to raw_smp_processor_id. > >> > >> I think it's best to make this a raw lock. At this chance, some > >> read-only users of vm_list should be rcu'ified. Will have a look. > > > > vm_list is rarely used, for either read or write. I don't see the need > > to rcu it. > > Avoid that code under this lock expands the preempt-disabled period, > specifically under -rt, and specifically as the number of objects over > which we loop is user-defined. Good point; even under non-rt. (well, actually, cpufreq_notifier and kvm_arch_hardware_enable are already non preemptible, and the stats code should just go away?) -- error compiling committee.c: too many arguments to function -- 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/