From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758038Ab2EAPgr (ORCPT ); Tue, 1 May 2012 11:36:47 -0400 Received: from casper.infradead.org ([85.118.1.10]:35004 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756669Ab2EAPgq convert rfc822-to-8bit (ORCPT ); Tue, 1 May 2012 11:36:46 -0400 Message-ID: <1335886587.13683.153.camel@twins> Subject: Re: [RFC PATCH v1 3/5] KVM: Add paravirt kvm_flush_tlb_others From: Peter Zijlstra To: Avi Kivity Cc: "Nikunj A. Dadhania" , mingo@elte.hu, jeremy@goop.org, mtosatti@redhat.com, kvm@vger.kernel.org, x86@kernel.org, vatsa@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, hpa@zytor.com Date: Tue, 01 May 2012 17:36:27 +0200 In-Reply-To: <4FA001D8.6080801@redhat.com> References: <20120427161727.27082.43096.stgit@abhimanyu> <20120427162401.27082.59387.stgit@abhimanyu> <4F9D32B4.8040002@redhat.com> <1335865176.13683.120.camel@twins> <4F9FBF38.2060903@redhat.com> <1335869827.13683.133.camel@twins> <4F9FD337.5010908@redhat.com> <1335884353.13683.144.camel@twins> <4FA001D8.6080801@redhat.com> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2012-05-01 at 18:31 +0300, Avi Kivity wrote: > On 05/01/2012 05:59 PM, Peter Zijlstra wrote: > > On Tue, 2012-05-01 at 15:12 +0300, Avi Kivity wrote: > > > local_irq_save() is a stronger version or rcu_read_lock() > > > > Not so, local_irq_save() doesn't at all stop regular RCU grace periods, > > things like preemptible rcu can be driven from rcu_read_unlock(). > > > > Note that this is the reason call_rcu_sched() exists and is used in this > > case. > > Ah, thanks for the correction. I'll read some more about the _sched > variants. Basically: rcu_read_{,un}lock_sched() -- aka preempt_{en,dis}able() call_rcu_sched() synchronize_rcu_sched() -- aka synchronize_sched(); Define an RCU variant where each cpu has to have scheduled at least once to complete a grace period.